Tag Archive for: Herb Stevens

Herb Stevens

Skiing Weatherman: More Snow Coming. No Kidding.

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Late Season Snow Opens Nordic Opportunities.

As the coronavirus situation has continued to unfold and expand, the curtain has all but come down on the alpine season across North America. Nevertheless, lovers of the great outdoors continue to find ways to ingest their fair share of fresh air by a variety of different means, including cross country skiing aficionados. At last count, 17 Nordic centers around the country remain open.  For those of you who will continue to rack up the kilometers as we move through early spring, here’s this week’s weather outlook.

This season now has all the earmarks of ending up with bookends in terms of jet stream patterns. You may recall that November got us off to a quick start as the jet stream aligned itself in a fashion favorable for the delivery of early season cold to the lower 48 states. Here in the East, as the calendar turned from October to November, the folks at Killington were very nervous about the prospect for the Women’s World Cup event scheduled for late that month. However, when the Women’s White Circus showed up three weeks later, the reversal of weather fortunes made for another hugely successful weekend of racing.

And then came the rest of the winter. As I discussed a couple of weeks ago, the Midwest and East got locked into a highly unfavorable jet steam setup that, unfortunately, made it very difficult for cold air masses to stick around for a while. Well, that appears to be about to change, which should help to extend the Nordic season.

In a nutshell, an upper level trough is going to set up shop over the eastern half of North America later next week. At the same time, a blocking ridge will be in place over Greenland. It was the LACK of a blocking ridge in that position that allowed cold air masses to slide right off the continent when they did manage to make a push into the Midwest and East. Cold air is not as abundant as it was one or two months ago, but there is enough available to flow into a trough and lead to late season snow. That scenario is on the table around April 3-5 in the Northeast. Here is a look at the expected pattern on the morning of the April 3:

A deep trough centered over eastern New York will provide the focus for the cold air. The trough may want to progress eastward into the north Atlantic, but the ridge that extends from Labrador to Greenland will resist and force the trough to only slowly move toward the ocean. It is important to also know that near the center of circulation of troughs, the air is rising and cooling to a greater extent than at points further away from the center. This further suggests that eastern New York and northern New England could very well pick up a substantial late season snowfall next weekend. That’s great news for Nordic touring centers from the Adirondacks to the mountains of Maine. As long as the ridge remains over Greenland, the colder air will stick around, just like in November.

Here Are The Regional Details.

Northwest U.S./western Canada: A season of abundant snowfall shows no signs of quitting. The hits will keep on coming in this part of the world for the next couple of weeks at least.

Sierra: While the amounts won’t be as prodigious as further north, the proximity of a trough not far offshore should produce several meaningful snowfalls in the next two weeks.

Northern Rockies: The storms that continue to bury the coastal ranges will move inland and keep this part of the U.S. and adjacent Canada in the crosshairs for solid snowfalls for the foreseeable future.

Central and southern Rockies: In the absence of an El Nino, it is tough to grind much snow out of the southern branch of the jet stream late in the season. Northern stream systems will graze these areas from time to time and provide several lighter snowfalls.

Midwest: Other than across the Upper Peninsula of Michigan, snowfall is a long shot the rest of the way in the middle of the country.

Northeast/Quebec: Next weekend looks like the best opportunity for late snow. Based on what has happened the past few weeks, northern Maine and adjacent Quebec won’t see bare ground for many weeks to come.

Thanks for reading. Enjoy your sliding and your summer.

Herb Stevens

Skiing Weatherman: There’s Snow In The West, Only Maybe East

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For Those Still Venturing Out On Snow Shoes, Skinny Skis, Or Skins.

On a typical office day in the winter, I often scan web cams from resorts, living vicariously on those days when I can’t be on the snow myself. Now that the coronavirus pandemic has ground the winter sports season to a virtual halt, I still check out the cams, but recently I have felt more of a sense of sadness rather than excitement or anticipation of my next trip to the mountains. The absence of skiers and the stationary lifts is striking, and where fresh snow has fallen and remains untouched, the scenes are downright bizarre. Although the alpine resort options are very limited, there are many of you who still want to get your fresh air on skins, skinny skis, or snowshoes, or perhaps with your grandchildren on a sledding hill, and it is for you that I present this week’s weather discussion.

The winter pattern has shown a great reluctance to change from a dominant western trough/southeastern ridge configuration, which has led to abundant western snows and a struggle for snow lovers in the Midwest and East. For the past two weeks, there have been signs of change in the Pacific that correlate to colder than normal weather spreading into the eastern half of the country and that change makes sense based on the change of seasons. You see, as we head toward spring, the distance between jet stream features shortens as the available supply of cold air in the hemisphere starts its seasonal decrease. If you think of that cold air as one large puddle in the heart of winter, it becomes smaller puddles as the overall supply dwindles. Each winter trough requires a cold pool aloft to exist, but with less cold air around, those features tend to be smaller than a month or two ago. So, rather than have two large features covering the continent, there is room for three, or even four from the eastern Pacific to the East coast. It is possible to have a western trough AND an eastern trough with shorter wavelengths. This jet stream forecast for next Tuesday illustrates that setup.

Not only is there a deep trough off the West coast, which will deliver another significant snowfall to the Sierra, Cascades, and northern Rockies, but there is a departing trough over the Northeast. In addition, the ripple in the flow over the Plains is another package of energy that could turn into a deeper eastern trough and potential snow producer by late next week because it could become stronger as it moves into the East.

Looking further down the road into early April, there are conflicting signs as to whether or not the jet stream flow will tap any appreciable amount of cold air to sustain what is left of the season. The transitional months are easily the most difficult time to forecast. Judging the battle between the retreating cold and advancing spring warmth is a handful, and there are signs that the pattern will revert to one that is milder than normal over the East while the West continues in more of a wintry setup. I still think that the shorter wavelengths will deliver cold shots and late opportunities for snow to the Midwest and East, at least up until Easter weekend.

Here Are The Regional Details.

Northwest U.S./western Canada: Quiet weekend with systems from Alaska moving into the region next week, leading to a snowy period overall.

Sierra: Dry weekend with snows returning to region next week as an upper trough slides down the coast. Only issue is that if trough hugs the coast, snow levels will rise.

Northern Rockies: Sunny weekend. Coastal Pacific system will bring snow to the region by Tuesday and Wednesday…another system arrives next weekend.

Central and southern Rockies: Southern branch of jet stream has brought this area snow over the past two weeks, but it will be rather quiet for the next week. Nothing more than a little light snow at times.

Midwest: Late week snow will refresh surfaces across the north. Nice weather for the weekend. Next opportunity for snow late next week.

Northeast/Quebec: Chilly, dry weekend. No major storms next week, but an early week southern system could bring late snow to the northern mid-Atlantic areas. Overnight lows help preserve snow most nights.

Herb Stevens

Skiing Weatherman: Out Like A Lion

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March Won’t Be Ending Spring-like.

Although I had good intentions, I must confess that I did not get on the snow in the past week.  65 degree temperatures here in Rhode Island early this week didn’t help to inspire, for sure.  Much of the East has had a frustrating season, due to a lack of cold and snow, but the evolving pattern over the next several weeks is not going to please those ready to turn their backs on winter.  The pattern is going to change to one that delivers cold and snow into the country, first into the West but also to the East, where the colder pattern will persist for a longer spell than we have seen since early winter.  That is great news if you have plans to ski or ride Easter weekend!

In the short term, a massive high pressure center is going to deliver a seasonably cold weekend to the resorts in the Great Lakes and East.  In the West, the best news is that the Tahoe area is going to receive heavy snow during the second half of this weekend into early next week.  After a largely snow-free February, some lighter snow has fallen the past two weekends in the central Sierra but this event will deliver the load that the resorts really need.  Amounts will range from 1 to 2.5 feet with this storm.  Snow is headed for the northern Rockies this weekend, too, as this surface map from Sunday morning illustrates. 

 

Next week will turn milder again in the East, but not to the extent that we saw earlier this week.  The coastal system that impacts the Sierra this weekend will continue to rotate southeastward during the first half of next week, bringing snows to the southern Rockies.  While the upper level trough that produces that snow favors the West, an upper ridge over the East will keep it mild and deflect a storm up through the Great Lakes late in the week, and that track will be unfavorable for snow in the East.

Help is on the way to the East, though, in a classic case of “better late than never”.  Changes are underway in the Pacific in terms of the location of ridges and troughs, and we will soon see a configuration that has been rare this winter.  An upper ridge will set up shop over Alaska, with a trough south of that spot.   Here is forecast for the 22nd that illustrates the position of that ridge.

In addition to the strong ridge sitting over Alaska, notice the trough extending down from the southern flank of the polar vortex all the way to southern California…that will continue to benefit parts of the West.  With a clockwise flow around the ridge and a counterclockwise flow around the trough, you can see how the air will be directed from the Yukon into the northern Plains and then eastward through the Great Lakes.  As the trough presses eastward, it will spread the cold air into the East for the final week of the month and likely beyond.  The season will roll along in the West, while in the East, don’t despair, a solid shot of cold and snow will set things up for some nice Easter sliding.

Here Are The Regional Details    

Northwest U.S./western Canada:  Light to moderate snow this weekend followed by several dry days next week.  Light snows return Thursday, followed by a more substantial weekend storm.       

Sierra:  Good sized storm this weekend, the biggest since January.  Next weekend looks promising, too.  Longer term, eastern Pacific trough development will bring additional snows into April.             

Northern Rockies:  Moderate to heavy snow this weekend, light snows continue early in the week.  Next shot at snow later next weekend.  

Central and southern Rockies: Light to moderate snow this weekend, another shot at significant snow Tuesday as southern branch systems moves toward Four Corners.      

Midwest:  Nice weekend on the slopes.  Light precip early next week, snow across north, rain south.  Developing colder pattern will help sustain the season late month/early April.               

Northeast/Quebec:  Seasonably cold, dry weekend.  Milder next week, not so much for northern New York and New England.  Pattern change will make Easter viable for skiing, riding.     

Herb Stevens

Skiing Weatherman: Cold Air Scarce In The East

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What’s The Matter With The Polar Vortex?

The past week brought light to moderate snows to much of the West, including some much needed snow in the Sierra, a region that has missed out on storms for much of this winter. A three-day storm last weekend was very productive from the snow belt areas downwind of the Great Lakes through the higher peaks of northern New York and northern New England. Stowe, Smuggler’s Notch, and Jay Peak in Vermont were the lottery winners, with over three feet of snow piling up. A good friend and Stowe skier told me that every turn in the woods last Saturday produced a “face shot” of powder! My favorite resort in the world, Mont Sutton in Quebec, just over the border from Jay, had a three foot dump, as well, and their phenomenal “su bois” (glade) skiing was the best of the season.

While most of the West has enjoyed frequent snows through the heart of the winter, the eastern half of the country has had trouble lining up storms on favorable tracks, and snowmaking temps have been spotty, especially south of I-90. There have been several major snows across the far north, and at elevation, but even in those areas, mixed precip events have also passed through. The main problem has been pretty simple: a lack of deep cold air masses AND a lack of staying power of the cold air that managed to push south. In this piece, I thought I would touch on the reasons why cold air has been hard to come by this winter.

For most of the season, a low pressure center at the upper levels of the atmosphere has been sitting over the western portions of the Arctic. The Polar Vortex typically meanders around the high latitudes, and occasionally weakens and breaks down, and that is when chunks of very cold air migrate southward into the mid-latitudes, often supporting snowstorms in the process. Occasionally, the vortex moves bodily southward, and that is when we see the coldest air reach the U.S. This winter, the PV has been remarkably persistent in its size and position, and that has greatly limited the amount of available cold air. Here is a map of the jet stream showing the current PV.

So, cold air has been scarce and when it has managed to find the eastern half of the country, it has seldom lasted more than a couple of days before milder air returned. The lack of staying power is related to the lack of a blocking pattern over the North Atlantic. A high pressure ridge over Greenland does a nice job of buckling the jet stream over the U.S. in winter, allowing cold air masses to hang around and help produce multiple snow events. That ridge has been missing much of the winter, resulting in a flat jet stream flow across the country, which has tapped milder Pacific air and pumped it into the pattern. Here is a diagram to illustrate.

Notice there’s a low pressure center near Greenland, not the usual high pressure ridge. The counter-clockwise circulation around that feature helps sweep any cold off the east coast and out to sea. There are signs that the flow may be buckling more from mid-month on, which would help generate late snows and sustain the eastern season into April. We shall see.

Here Are The Regional Details.

Northwest U.S./western Canada: Trough offshore brings moderate to heavy snow into next week. After a couple of dry days, a stronger trough comes ashore with heavy snow later next week. The epic season continues.

Sierra: Trough digs down the coast from the NW over the weekend, producing light to moderate snows. Dry early next week, with southern branch trough moving inland late next week, bringing significant snow to the southern Sierra.

Northern Rockies: Weakening troughs produces light snow over the weekend into early next week. Next shot at major snow late next week from northern branch system.

Central and southern Rockies: Ridge aloft early with mild temps. Light snow later this weekend. Next significant storm late next week.

Midwest: Mild weekend with surfaces softening.   Lower Lakes looking at potential snow event later next week. No lake effect events in next week.

Northeast/Quebec: Nice weekend on the slopes. Next potential storm mid to late next week, likely another elevation event.

Herb Stevens

The Skiing Weatherman: Snow West, Maybe East

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The Pattern Persists.

In the past two weeks I have enjoyed many days on the snow, and a couple of them turned out feeling like reunions with old girlfriends. First came an afternoon at West Mountain in Glens Falls, NY, where new owners and $6 million in investments have turned a sleepy hill into a dynamic mountain that embraces racing for all ages. Got my skis tuned there, and the result was phenomenal!

Then I caught Wildcat, NH on a packed powder bluebird day. The long winding cruisers loaded with natural mini-features brought back memories of cutting high school in Rhode Island for twofer days on Wednesdays. The views of Mt. Washington across the street are beyond stunning. Wildcat summit view is the best in the East, IMO.

So, where are we going with the weather the next couple of weeks? The pattern has been rather persistent for weeks on end now, with abundant snow piling up over much of the West, the exception is the central and southern Sierra, where storms of significance have been rare this winter. In the Midwest and East, “persistent” has had a different meaning with mild and cold air masses taking turns marching through every four to six days. Storm tracks have favored a “cutter” type, where the primary low center moves through the eastern Great Lakes toward the St. Lawrence River Valley. A coastal secondary storm has formed with many of the cutters, but usually quite late—south of Long Island or Cape Cod—which has helped boost snowfall totals in New Hampshire and Maine as the low center heads for the Maritimes. However, at resorts further west, in VT, NY, and PA, the cutter has been more influential and most have produced a “variety pack” in terms of precip types.

There are a number of indices that help me put together longer range forecasts, such as the SOI (Southern Oscillation Index), MJO (Madden Julian Oscillation), AO (Arctic Oscillation) and NAO (North Atlantic Oscillation). For the most part, these indices have sent mixed signals in what has turned out to be a tough winter for forecasting over the eastern half of the country. The West has been much easier: ”Snow and more snow”.

One index that has performed admirably has been the EPO (Eastern Pacific Oscillation). When it is positive, we tend to see a trough over Alaska, which helps drive moisture into the NW, which accounts for the bountiful snow, but that Pacific air is mild when it reaches the lower elevations further east. When the EPO is negative, an upper ridge pokes northward to Alaska and helps tap colder air from the Arctic regions. This forecast of the EPO telegraphs the changeable nature of the temps going forward.

Following the green line, the neutral look to start with accounts for the chill of this weekend, with the rise next week foretelling a milder spell, followed by a drop and colder weather thereafter, a sequence that mimics what we have experienced for quite a while.

The decade of the 10’s was the most active on record in terms of sizable coastal snowstorms in the East, but the first winter of the new decade has pitched a shutout to this point. That said, there are signs that the forces might conspire to bring the Northeast a late season dump during the colder dip in the EPO. Here is a look at the European forecast for the 7th of March. A man can dream can’t he?

Here Are The Regional Details

Northwest U.S./western Canada: Onshore flow from the Pacific will keep the snow coming, broken periodically by a short wavelength ridge passing through. Many powder days coming through mid-March.

Sierra: Some much needed snow is coming to this region early in the week of the 2nd. Another shot comes along about a week later.

Northern Rockies: I don’t see a whopper on the horizon, but a moderate snowfall will come along every few days in the next two weeks

Central and southern Rockies: Light to moderate snow event 3rd-5th followed by upper level ridging and bluebird skies late next week.

Midwest: Lake effect snow early in snowbelt areas. Clipper systems bring additional snow during EPO dip.

Northeast/Quebec: Back and forth temperature ride continues into mid-March. Snowfall highly storm track/elevation dependent. Some signs of coastal storm around March 6-7 starting to show up.

Herb Stevens

Skiing Weatherman: A Battle For The Second Half

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Post-Ground Hog Day Winter Looks Like A Struggle Between Air Masses. The Winner Determines the Outcome Of The Season.

Over the past week, the Northwest and northern Rockies have been the overall winners in the snowfall lottery, continuing a trend that has been in place much of this winter. Over the eastern half of the country, it has been a struggle to pile up snowfalls. More often than not, storms have produced a mix of precip types because of an unfavorable storm track or simply just a lack of available cold air. This discussion is going to focus on the Midwest and East, because a battle for the outcome of the season in those regions is getting underway. What I mean by that is cold air is trying to push southward out of Canada but milder air associated with an upper ridge over the Southeast just won’t go away. While the next couple of weeks look snowy, there are signs that the ridge may push back and cause the storm track to shift northward late this month.

The day this is posted, a juicy storm is delivering heavy snow to a swath of the Northeast from upstate New York to western Maine. Further south, snow is also falling on the heels of another round of mixed precip. The dramatic thermal gradient between the contrasting air masses is responsible for the storm and if we look at the outlook for temperatures at 5,000 feet for Friday (2/7), you can see the essence of the fight.

The border between blue and green is the 32 degree line, which approximates where the rain/snow line is likely to be. The line has cut across the East, and at times the Midwest, in most storms this season, causing a wide variety of precip types and changeable conditions.

Last week I wrote about the cold that was finally asserting itself again, and it will be available for storms through at least mid-month, so I am confident that more snow will fall north of I-80 or so. Beyond that, I have some concerns about the staying power of any cold, based on whether or not the EPO, or Eastern Pacific Oscillation, will stay negative, where it is now. A negative EPO, where an upper ridge is found over Alaska with an upper trough underneath it and off the west coast, correlates with colder than normal temps over the eastern half of the country. That helps turn more water vapor into snowflakes rather than those less desirable forms of precipitation. There are signs that the EPO will trend positive later this month, with a trough returning to Alaska. That would inject milder Pacific air into the pattern which would squeeze the rain/snow line further north once again. Here is a forecast for the EPO going forward.

It is not forecast to go strongly positive, but still enough to potentially limit the push of the cold air from southern Canada. I will have more in my next post, but in the meantime, enjoy the snowy pattern unfolding from the Lakes to the Northeast.

Here Are The Regional Details

Northwest U.S./western Canada: Disturbances will slide down the coast along the eastern flank of the ridge over Alaska and deliver moderate to locally heavy snowfall every two or three days through the next week. The parade will continue into Week Two.

Sierra: Ridge offshore is “too close for comfort” in Week One as most storms are deflected to the east. Week Two looks more promising for fresh snow.

Northern Rockies:  Systems cutting southeast into the region will maintain enough moisture and power to keep the snows coming every few days Week One into Week Two/

Central and southern Rockies: The storms that hit the NW/N Rockies will produce a snowy Week One in the central Rockies. Light to moderate snows further south in NM/AZ. Week Two looks better.

Midwest: Two snowfalls north of I-80 in Week One will refresh the slopes nicely. Alberta Clippers will bring additional snow in Week Two. Packed powder to rule in most of this region.

Northeast/QB: Early storm sets things up for a nice weekend from central NY through Adirondacks, northern Greens/Whites and western Maine.  Same areas hit again later next week. Mixed precip south of these areas.

Herb Stevens

Skiing Weatherman: Winter Is Delivering

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Looks Like A Promising Couple Of Weeks.

It has been a terrific week of skiing and riding in most of the U.S. and Canada and I have been lucky enough to squeeze in a couple of days. Loon Mountain on Tuesday was wonderful; miles and miles of packed powder and views of the White Mountains that are hard to beat. Packed powder, sunshine, and light winds at Stratton on Thursday added up to another awesome day.

The pattern looks very promising for the next couple of weeks, but it is not without its challenges. The primary challenge arises from a jet stream development over the northeastern Pacific that quite honestly, I had not anticipated. With a sizable pool of warmer than normal water over that part of the Pacific, I expected an upper level ridge to be a persistent feature that would extend northward to Alaska. Instead, a trough is parked over Alaska and the counter clockwise circulation around it cuts off cold air from the high latitudes and pumps milder Pacific air into the southern Canada/U.S. pattern instead. Temps will be above normal over Canada for the next ten days or so as flat ridging dominates there. Does that mean that it can’t snow over the northern tier of states? Not at all, because we are at the climatologically coldest time of year. However, each storm will be a nail-biter for snow vs. rain in the Midwest, northern mid-Atlantic, and Northeast. Here is a forecast map for the jet stream across the continent for later Saturday, Jan 25, that illustrates the issues.

The trough off the west coast that stretches northward to Alaska is tapping relatively mild air and sending it into the Northwest and mountains of B.C. There is a ton of moisture available, but snow levels will be an issue in WA and OR this weekend…not so further north in B.C. The moisture will flow east and the northern and central Rockies will benefit with moderate amounts of new snow later this weekend.

 

The red shades that you see across Canada indicate the extent of the ridge that will play a major role in this weekend’s event in the Northeast. Although it is mild relative to normal over the eastern half of Canada, that air is still cold enough to support snow. Also, upper ridges support surface high pressure centers that can deliver low level cold air into the path of a storm. Just such a high will be present over Quebec this weekend and it will help produce snow in the Adirondacks, Greens, Whites, and into the mountains of Maine. Further south it will turn into more of an elevation-dependent tossup. The upper ridge will help suppress the trough you see over eastern Ohio and it will track east…favorable for the snow to the north. The upper ridge will also keep the surface low from racing out to sea, so the snow will be a 48-60 hour event. Here is a snowfall forecast map through Monday night…it is great to see that significant snow will reach southward to West Virginia resorts…they are running a little lean right now.

Longer term it looks like the same general pattern will remain in place for the next 10-14 days, with another eastern storm in the cards late next week. After that, the western ridge should poke north far enough to deliver a fresh shot of cold to the lower 48.

Here Are The Regional Details

Northwest U.S./Western Canada: B.C. will see very heavy snow this weekend. WA and OR Cascades pick up heavy “cement” as snow levels start high and slowly drop. Same general setup holds through next week.

Sierra: Snow—perhaps a foot—Saturday night/Sunday Tahoe regio. Snow levels dropping through the event. Lighter snows southern Sierra. Some light snow next week; main storm track to north.

Northern Rockies: Moderate snow will develop later this weekend from Pacific trough. Wasatch, Tetons and points north looking snowy next week.

Central and southern Rockies: Dry weekend. Light snow early next week central, just snow showers south.

Midwest: Light snow north this weekend, mixed precip WI and lower MI. Another shot at snow later next week.

Northeast/QB: Long duration light to moderate snow event this weekend, north of I-90. Elevation snow between I-80 and I-90. Snow south to WV along Appalachian spine. Another storm late next week.

Herb Stevens

Skiing Weatherman: For The East, Enter Winter

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A Comeback For The East And Midwest, More Pow For The West.

I spent the first two days of this week with fellow members of the North American Snowsports Journalists Association at Windham Mountain,  NY, where the crew did an outstanding job of providing a fun surface in the wake of a mid-season meltdown last Sunday. One of the presentations was by Masterfit University, an outfit that boasts having the best boot fitters in the world. It was a fascinating seminar, and after spending a couple of hours one on one with Windham’s Masterfit representative, I came away convinced that if you want to maximize your skiing, you absolutely should find a Masterfit shop in your area.

While this week started on an unseasonably mild note in the East, the skies kept unloading in parts of the West. A persistent series of low pressure centers loaded with Pacific moisture has utterly buried resorts in Washington, Oregon, northern Idaho, the Tetons, and northern Wasatch in the past week with anywhere from three to six feet of new snow. Lookout Pass in Idaho checked in with a 101 inch storm total! Lighter snows fell elsewhere in the West, and if you are heading in that direction, you can’t make a bad choice right now.

In the Midwest and East, a major pattern change is getting underway, one that delivered some fresh snow in the mountains of the Northeast late this week, with another round coming this weekend. For the first time in weeks, once the low pressure center moves through the Great Lakes and East, a bonafide cold air mass will follow in its wake, leading to great snowmaking conditions and productive lake effect snow in favored snowbelt areas, especially the upper peninsula of Michigan.

Over the next 10 to 14 days, temperatures will be stepping down over the eastern half of the country as an upper level trough becomes the dominant jet stream feature. At the same time, an upper level ridge will be found more of the time in the Northwest, so the “snow hose” that has been pointed at that region lately will back off quite a bit. The southern Sierra and southern Rockies could see periodic snows as disturbances in the southern branch of the jet move through that part of the country. If a southern branch disturbance manages to phase with energy in the eastern trough, we could see a major storm in the East before too long. The pieces will all be there soon and hopefully they will come together. For your viewing pleasure, here is a forecast map of snowfall for the next 15 days. Don’t focus on one specific spot as much as take note of the breadth of the area, particularly over the eastern half of the country, where significant snow is forecast. The pattern is rounding into shape for meaningful snow events, but the devil will be in the details.

There is reason to believe that once the colder pattern gets established in the Midwest and East, it will remain in control much of the time going forward. My analog years suggest it, as does this jet stream map for two weeks from now:

 

The broad trough that you see for late this month looks cold and stormy to me.

Here AreThe Regional Details

Northwest U.S./Western Canada: Another rather snowy week coming up, but the recent amazing rate of snowfall will start to back down as an upper ridge takes up residence.

Cascades and Sierra:  Snowy (Cascades) into the middle of next week, although snow levels will be a little high late this weekend before settling back down. Lighter snows Tahoe area. Snowfalls back off late this month as ridging develops.

Rockies: Dry weekend into midweek when a new trough will bring some light snow. Longer term, central and southern Rockies favored for snow thanks to disturbances in the southern branch of the jet stream

Midwest: Arctic air dominates for the foreseeable future. Each frontal passage sets off lake effect snow. Great spell of snowmaking temps underway and conditionS.  Trail counts will be improving.

Northeast/QB: Moderate snow event this weekend (north of I-80) starts the comeback. Great snowmaking temps for several days in the wake of the storm. Another sizeable snow threat next weekend. Conditions and trail counts will be getting better each day until further notice.

 

 

 

Herb Stevens

The Skiing Weatherman: Changeable East, Snowy West and Mid-West

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The West Continues To Luck Out, Cold Coming East By Month End.

Despite a wildly changeable run of weather in the East recently, I managed to get two days of wonderful winter turns in early this week. It snowed on Monday at Sugarbush as I skied packed powder with my son. Wednesday at Killington surfaces were just about perfect packed powder early on and then an arctic cold front arrived. It brought fresh snow: three inches in 30 minutes! An absolute whiteout that gave me a chance to focus on my toes with each turn, a method I was taught decades ago to deal with low visibility. It still works!

Changeable weather will continue to rule short term in the East while much of the West continues snowy, but that imbalance will be changing in the near future. The past couple of weeks, the jet stream maps across the continent have featured a trough centered over the West and a ridge over the East. The trough has produced tons of snow, particularly in the Northwest and coastal ranges of British Columbia.

As this week comes to a close, another storm will cut southeast from the Gulf of Alaska and dump on B.C. as well as the WA and OR Cascades. Lighter snows will reach down to Tahoe as well as the northern and central Rockies. Over the eastern half of the country, a low will cut northeastward through the Great Lakes and into Ontario and Quebec.  That’s great news for the resorts of Michigan, where significant snow will result. Further east, the northern track forced by the strength of the southeast ridge means another mild, wet event this weekend before colder air returns Monday. The “cutter” track is consistent with the current warm state of the MJO, as discussed last week.

Changes are coming, though, and by the final week of the month, the changes will be dramatic across the country. A pool of very cold air has been building in central and western Canada and due to the density of that air mass, it will start to spread southward and eastward. Here is a look at a forecast for the 5,000 foot temperature anomalies for ten days from now that I agree with.

The 5,000 foot level is a forecasting proxy for surface temps, and you can see that a large mass of colder than normal air will cover much of the eastern half of the country by 19th or so. Meanwhile, the West will turn a little warmer than normal, but not until after some of the arctic air descends through the Rockies later next week. At the jet stream level, the setup will flip, and we will find a trough in the East and a flat ridge out west.  Here is a reasonable jet stream forecast for the same time.

Now, any change in air masses and jet stream features of this magnitude will come with a stormy transition, so there is reason for optimism for eastern snow, at least north of the Mason Dixon line, from late next week onward. Once the new pattern settles in, I expect it to dominate through the bulk of rest of the winter, due to the anticipated influence of the warm water pool in the northeast Pacific Ocean.

Here are the regional details.

Northwest U.S./Western Canada: Another heavy snowfall is coming this weekend, light snow in AB.

Periodic lighter snows will continue next week as arctic air presses southward.

Cascades and Sierra: Snowy weekend with heavy amounts in OR, tapering down further south in CA.

Lighter snow continues next week as it turns windy and colder.

Rockies: Northern Rockies catch light snow this weekend but as several upper level short wavelength disturbances move through the first half of next week, persistent light to moderate snow will provide daily “refills”. Each successive trough will draw arctic air further south, reaching the Tetons by mid-week. Light snow in central Rockies first half of next week.

Midwest: Messy weekend storm lower Lakes, snowy in northern Lakes, narrow ice storm in the middle.

Some light snow northern Lakes from a Clipper or two next week.

Northeast/QB: Another cutter brings wet and icy weather to the northern mountains of NY/New England this weekend, snow up in Quebec. Renewed snowmaking and light Clipper snow next week, with bigger storm threat late. Pattern will look much better a week from now.

 

Herb Stevens

Skiing Weatherman: Global Pattern Bringing Warmth Then Cold Mid-Month

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Happy New Year To All Of My Fellow Senior Sliders!

In the two weeks since my last post, the western slopes of the U.S. and Canada have been the unquestioned winners in terms of fresh snow. Just prior to Christmas, the trail counts from British Columbia south to the Sangre de Cristos of New Mexico were on the lean side, but a persistent parade of moist troughs started marching ashore from the Pacific. Those systems produced an overall snowy pattern that jacked up those trail counts dramatically. There are a few resorts here and there that got slighted by Mother Nature, but by and large, it is hard to make a bad choice out west.

While troughs produced the goods on one side of the country, flat ridging at the jet stream level have made fresh snow rather scarce in the Midwest and East. Fresh shots of cold air have been more of a glancing blow, but resorts in the northern Great Lakes eastward through the mountains of northern New York and New England have maintained their trail counts for the most part through the holiday period.

So, where are we headed from here? Well, a pattern that can best be described as changeable will unfold during the first half of January. As such, I think that there will be opportunities for resorts all across the country to enjoy some fresh snow. I still believe that we will eventually see a western ridge/eastern trough couplet become more favored, but there are too many conflicting signals coming from the Pacific for the jet stream to settle into that set up just yet.

The factor that seems to have the most impact on our weather right now is the MJO, or Madden Julian Oscillation. The MJO is all about convection that forms in the Indian Ocean and tracks eastward into the southwest Pacific. Madden and Julian divided the track into eight sectors and noticed that there were significant correlations with weather over North America, with a lag of 7-10 days, depending on where the thunderstorms were clustered.   Right now, the convection is fired up north/northwest of Australia, as you can see in this infrared satellite picture.

If you follow the green line in the chart below—each black dot is one day—you will see the MJO making a move into octants 4 and 5 in about a week. [Editor Note: octants 4 and 5 represent continental North and South America.]

Using the temperature correlation maps below, you can clearly see that octants 4 and 5 are warm over much of the country, and I believe a warmup will occur mid-month before the pattern turns colder again.

Before any warmth reaches the East, though, Midwest and Eastern resorts—north of the Mason Dixon line—will pick up fresh snow at least a couple of times. The first event will be this weekend as a storm cuts southeastward to the mid-Atlantic coast before turning up toward New England, with an Alberta Clipper sliding through the East a couple of days later. Big winners in the snow derby the next week or so in the West will be the Cascades, northern Rockies, and the resorts of B.C.

Here are the regional details.

Northwest U.S./Western Canada: Healthy storm nails B.C. this weekend, with another system arriving later next week.

Cascades and Sierra:  Light to moderate snow in the Cascades this weekend. Northern system late next week looks productive in WA/OR, but the Sierra will only receive lighter amounts.

Rockies: Late this weekend/early next week the Rockies will pick up light to moderate snow (north) and generally light amounts south of I-70. The Tetons and Wasatch are in line for moderate to heavy snow late next week.

Midwest: Early week Clipper system will deliver light to locally moderate snow, with the best snowmaking temps in a while following. That cold air will also support lake effect snow in northern parts of the lower peninsula of MI.

Northeast/QB: A system this weekend will turn into a moderate to locally heavy snow producer from WV northeast into New England and southern QB. A Clipper system will follow in the middle of next week with the potential for additional light to moderate snow.

 

 

Herb Stevens

Skiing Weatherman: All Is Calm

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Except The West Coast.

Last week I discussed the role of upper level troughs as they relate to our insatiable appetite for fresh snow, both natural and machine made. Most of the time, troughs are indeed our friends but that doesn’t necessarily mean that upper level ridges are the enemy. The influence of ridge is just like the old cliche about real estate: location, location, location. Troughs often look like the letter “U” on a map while ridges tend to take on the shape of the Greek letter Omega. I have used a jet stream forecast map for Sunday the 22nd to illustrate this common configuration.

Now, in order to take on the Omega shape, you can see that the two ends of the line are wrapped around adjacent troughs, and that is where the location piece comes into the equation. You see, ridges are areas where overall, the air is sinking. Sinking air limits cloud cover and precip, and it also warms up as it sinks, consistent with the laws of physics. So, if you find your favorite resort under a ridge, your odds of seeing snow are greatly reduced. But, if that same ridge is off to the west of the resort by several hundred miles or more, the clockwise flow around the ridge will work together with the counterclockwise flow around a downstream trough to the east to tap cold air from the north. At that point, the ridge becomes your ally. As I have expressed in earlier posts, I am confident that a western ridge/eastern trough couplet is going to be the favored setup as we head through this winter, but in the shorter run, the ridge is going to spread out and cover much of the eastern two thirds of the country as we head through the holidays. Overall, Pacific systems will bring seasonable cold and some snow to the west while it is milder than normal east of the Mississippi.

Here Are The Regional Details.      

Northwest U.S./Western Canada: A very juicy storm will be in progress into this weekend. Whistler finally gets tagged. Cascades get healthier trail counts. Pattern more benign next week.

Cascades and Sierra:  The same storm will nail the Cascades. Snow levels will be rising through the storm, so only count on “all snow” above 6K feet. Amounts will be 2-3 feet WA and OR. CA Sierra pick up moderate snow Sunday. The pattern will turn quieter through most of Christmas Week.  

Rockies: The coastal storm will slow coming inland due to the spreading of the upper ridge further east, so any snow that makes it out of the Cascades will be spotty and light late this weekend/early next week. No big storms next week by the looks.

Midwest: Late week lake effect will help set up this weekend. Milder temps develop into next week, which limits snowmaking windows. The good news is, it looks rather dry, under the ridge, Christmas week.   Colder air returns after the 29th or so.

Northeast: Late week shot of Arctic air will allow snowmakers to get busy 24/7 in most spots. It will turn milder next week and snowmaking will be feasible in the mountains. The lower elevation areas should have some windows, too. With the ridge axis fairly far to the west next week, some colder air will filter into the region at times. No significant snow events appear to be in the cards through the end of next week.  

Overall, after a major “Cascade Cement” storm in the NW at the outset, the holiday period looks rather dull from a forecaster’s perspective. Some lighter snow will fall in the west…the milder temps will keep it comfortable on the slopes for skiers and riders in the Midwest and East.       

Herb Stevens

Skiing Weatherman: How A Trough Works

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And Regional Forecasts From West To East.

Had my first day on snow last Thursday at Jiminy Peak in the Berkshires. It was a wonderful day on nearly perfect snow: chalky packed powder with some windblown pillows of powder along the edge of several trails.

Today, I thought I would tell you about the jet stream feature to look for when you are hungry for snow or cold weather.

For the most part, troughs are your friends. On a map they look like the letter “U” and act as receptacles for cold air delivered from Canada. They also provide the upper level support for surface low pressure centers to form and deliver fresh snow. There are two “branches” of the jet stream that flow across the continent in the winter, northern and southern. Northern troughs tap into the cold from Canada, and southern troughs enhance the injection of moisture into surface lows. When the two branches combine, or “phase”, we often see our strongest storms. In the West, single branch systems can be pre-loaded with moisture as they roll ashore from the Pacific, so phasing isn’t as necessary to generate a major snowfall. The next opportunity for a significant snowfall in the East will come next Tuesday, when some phasing looks possible. This jet stream map for Tuesday night illustrates the attempt at phasing:

 

Notice that the southern branch feature is lagging behind the northern one. If it catches up to the longitude of the northern branch system, the storm will be more intense.

Here is the surface map that goes along with that trough at that time:

The High to the north, in Quebec, will feed the system with cold air and should suppress the track to the south far enough to keep most of the NE in moderate snow.

Next week I will discuss the role of upper level ridges in winter weather.

Here is the outlook for the next 1-2 weeks, by region.

Northwest U.S./Western Canada: Light to moderate snow has fallen in BC in the past week with heavier snow in Alberta helping to boost skiable acreage. With the eastern Pacific ridge temporarily replaced by a trough for much of the next couple of weeks, new snow should be significant.

Cascades and Sierra:  A much needed juicy storm hit the Sierra last weekend and open terrain percentages took a major jump. Late this week, the Cascades are cashing in, and totals will be two-four feet when the storm winds down over the weekend. Tahoe will pick up five-10 inches. Cascades will also be hit by a moderate storm early next week. Additional troughs will arrive every few days up until the holiday.

Rockies: The northern branch storm that nails the NW will bring heavy snow to ID, MT, WY, northern UT and northern CO over the weekend. One-two foot totals look likely. Like the coastal ranges, the northern half of the Rockies can expect additional helpful systems in the next 10-14 days. The southern Rockies will see lighter snow this weekend, but will have to wait for a southern system for help…later next week at the earliest.

Midwest: Lake effect snow has helped this week, especially in northern Lower Michigan, but it looks as though the air that flows over the Lakes in the next week will not be as cold, so amounts will be modest. An Alberta Clipper or two next week could help the northern Lakes, in addition to pretty solid snowmaking temps.

Northeast: Early week rain was followed by outstanding snowmaking temps this week but another wet storm will move through Saturday, due to a track that hugs the coast too closely…some backside snow will occur across northern New York and New England on Sunday. Prospects are better for a meaningful snow event on Tuesday/Wednesday of next week. Cold air will not be abundant, so there will be an elevation component to the storm. The snow should provide a shot in the arm to resorts roughly north of I-80. Longer term will be a high wire act leading up to Christmas, as the progressive pattern will make it difficult for cold air to get locked in enough to ensure snow vs. rain. There will be enough cold intervals for helpful snowmaking, however.

Overall, the weather in the Western half of the country looks good while the pattern will be rather chaotic with an enhanced degree of variability over the Eastern half for the next 10-14 days.  

 

 

Herb Stevens

Skiing Weatherman: Regional Outlooks

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By the time this piece is posted, I will have enjoyed my first turns of this season, at Jiminy Peak in the Berkshires.  The skiing should be superb after more than two feet of new snow from the early week storm.  It was a slow mover and got stretched out from west to east due to a blocking pattern to the north, and the axis of the heaviest snow shows that dramatically…take a look. 

It was a major shot in the arm from the Catskills and upstate New York eastward through Massachusetts as well as in southern VT and NH, but further north in New York and New England, amounts were much lighter. 

The Midwest has benefitted from a parade of Alberta Clipper systems and some lake effect snow in the past two weeks, and trail counts have been slowly climbing in the center of the country.  The West benefitted from a series of storms in late November that hit the southern Sierra and southern and central Rockies, (Five+ FEET at Mammoth and Alta).  We all know that it takes more than one healthy storm to get things really rolling in that part of the country but recent storms have certainly helped.  The Cascades and northern Rockies have been in a quiet pattern for the most part, due to the influence of an upper level ridge that has been persistent over the western edge of the continent from Oregon northward to Alaska.  That jet stream ridge will likely be dominant this winter, due to the large pool of anomalously warm water that is present in the northeast Pacific, as we have discussed in a previous post.

So, with less than three weeks to the holiday period, every winter sports region in the country could use fresh snow, or at least consistent cold and dry weather for snowmaking.  Here are the prospects for the next couple of weeks, broken down by region.

Northwest U.S./Western Canada:  Recent snows have helped in the coastal ranges of B.C. with interior B.C. and Alberta getting some help, too.  However, the ridge looks like the dominant player the next couple of weeks but systems that weaken as they approach the coast should produce some light to moderate snow on at least a couple of occasions.

Cascades and Sierra:   A weekend storm will produce one to three feet in the Sierra, with the storm bypassing Oregon and Washington, where the ridge will hang tough.  The southern extent of heavy snow should reach Mammoth, but taper off quickly further south.  Any system that reaches the southern ranges next week will not be nearly as dynamic.

Rockies:  The northern Rockies will see some light to moderate snow at times, but no major storms, as the ridge will knock down the strength of any systems that fight their way inland after most of the moisture is wrung out by the coastal ranges.  A new, deep trough will take shape over the eastern half of the country next week and disturbances sliding down the western edge of the trough could produce some snow in WY and CO.  The southern Rockies will have to wait for another batch of southern stream systems but overall, the southern branch does not look too busy going forward.

Midwest:  After a mild, wet start to next week, this region will see a more favorable pattern develop.  A new, cold trough will take shape and deliver arctic air by midweek.  That air mass will set off widespread lake effect snow, Alberta Clipper systems will cut across the Lakes in the days to follow, and temps will be conducive to very productive snowmaking much of the time in the next two weeks.

Northeast:   Pretty much the same as the Midwest, with a one day delay for the arctic air.  Snowmaking, snow showers, and grooming will rehab the surfaces by next weekend and cold and occasionally snowy weather will dominate the next two weeks of holiday prep. 

For reasons not fully understood, the persistence of weather patterns is enhanced during times of low solar activity, especially blocking patterns.  We are very close to the bottom of the 11 year solar cycle, as shown here.

Working together with the northeast Pacific warm pool, persistence and blocking will favor the eastern half of the country this winter.   

Herb Stevens

The Skiing Weatherman: Haves And Have Nots

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The Difference Between East and West Is Remarkable.

Over the past few weeks, I have shared with you some of my winter forecasting tricks of the trade but now it is time to get down to business and do some actual forecasting. 

The pattern change that was foretold a couple of weeks ago by the re-curvature of a typhoon east of Japan is well underway (The “Typhoon Rule”). By this weekend an unseasonably cold upper trough will cover the eastern half of the country.  The air that the trough delivers will be of arctic origin, and, although it travels over ground that is not yet covered with snow, it will still be cold enough for some productive snowmaking in the taller mountains of the Northeast and as far south as resorts in the central Appalachians. 

Better yet, the cold air will rush in on the heels of a low pressure system that will generate a swath of snow from the Great Lakes eastward to the interior Northeast.  Lake effect snow will kick in downwind of Erie and Ontario for a short time, but because the system will be progressive, that backside snow won’t last very long.  This looks like a three- to six- inch event from the Adirondacks eastward through the Greens and Whites and on into the mountains of Maine.  That may not seem like much, but that first inch of machine made snow is laid down a lot faster when it lands on crystals and not leaves and dirt.  The cold temps this weekend will help to chill the soil, too.

On a broader scale, the developing pattern will be one of the “haves” and the “have nots” with respect to cold weather and prospects for snow.  Here is what the jet stream pattern is likely to resemble late next week

The deep trough will cover much of the eastern half of the country, with a strong ridge covering the waters of the eastern Pacific.  Clockwise flow around the ridge will combine with counterclockwise flow around the trough to tap into air masses from far to the north. This setup is ideal for the delivery of cold to the Midwest and East.  This next map shows the expected temperature anomalies at the five thousand foot level in a week from now. That altitude level is a proxy for forecasting surface temps.

The purple shading tells me that the air will be plenty cold for snowmaking and natural snow opportunities from the upper Midwest through the Northeast.  That takes us to the middle of the month, but my sense is that the same general pattern will persist until after the 20th or so, and perhaps close to Thanksgiving.  From time to time, smaller scale disturbances embedded in the flow around the trough will spin through the Lakes and into the East, and those systems will represent the best shots at natural snow over the next couple of weeks.

That is the good news.  While eastern North America will be unseasonably cold for the foreseeable future, thanks to the trough, the not-so-good news is that the ridge over the Pacific will keep temps above normal for the most part from the Continental Divide westward, as the temperature anomaly map suggests. 

Some snowmaking will be possible at times in the higher elevations of the West, but natural snow will be hard to come by in this pattern.  In the heart of winter, there is enough cold air around for both the West and the East to be cold simultaneously, but we are still six weeks away from the START of winter, so we are playing the game of “haves” and “have nots”.  For now, it is “advantage Midwest and East”.           

Herb Stevens

The Skiing Weatherman: Knowing The NAO

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A Negative NAO IS Friendly To Skiers. Right Now, It’s Smiling.

During the upcoming winter I will be producing condensed regional forecasts on a weekly basis, hopefully providing readers with another nugget of info before they pick a destination for time on the slopes.  I will refer to a number of different reasons for forecasts that you will probably not hear from other sources.  Things like the Typhoon Rule that I wrote about last week and SSW (Sudden Stratospheric Warming) episodes.  In addition, I will use a number of “teleconnections” around the northern hemisphere. 

A teleconnection is a relationship between surface and/or jet stream level features located thousands of miles apart both west to east and north to south.  Each one has a correlation to different types of winter weather in different parts of the country.  Examples are the SOI (Southern Oscillation Index), AO (Arctic Oscillation), EPO (Eastern Pacific Oscillation), and MJO (Madden Julian Oscillation).  One of the most significant winter teleconnections for snow lovers east of the Rockies is the NAO (North Atlantic Oscillation), which I would like to explain today.

The components of the NAO are found over the waters of the North Atlantic and the teleconnection is based on the difference in sea level pressure between two persistent features: the Icelandic low and an Azores high.   The relative positions and comparative strengths of these features determine the sign (positive or negative) of the NAO. 

When the two systems are relatively strong, the interactive circulation between them (counterclockwise around the low to the north and clockwise around the high to the south) speeds up, which results in more of a zonal, or west to east flow across the Atlantic.  That setup makes it easier for cold outbreaks from Canada to be ushered offshore after only a brief visit to the central and eastern U.S.  This is an example of a positive NAO.

When the two systems are weaker, the flow can buckle more easily, not only at the surface but also aloft.  When that happens, upper troughs are favored over central and eastern North America and blocking ridges can be found in the vicinity of Iceland and Greenland.  This is the configuration when the NAO is negative. 

Jet stream patterns are more persistent when there is greater amplitude of troughs and ridges. When the NAO goes negative, the trough acts as a receptacle for cold air from Canada.  The development of such troughs often spawns surface storms, many of which bring snow to the Lakes, mid-Atlantic, and Northeast, often in the form of a disturbance that becomes a coastal “Nor’easter”.  It is worth noting that a correlation exists between low solar activity (we are now very near the minimum of the 11 year solar cycle) and North Atlantic blocking patterns that support a persistent negative NAO. So, there is reason to believe that the NAO will be in a mode friendly to skiers and riders at least a fair amount of the time this winter. 

Here are depictions of the two modes of the NAO…

Now that November is here I know that many or you are starting to get as revved up about the season as I am and you are looking for snow, or at least temperatures cold enough for productive snowmaking.  The Rockies have gotten off a fast start and the first shot of true cold air has reached the Great Lakes this week and will spread into the Northeast over the upcoming weekend.  The first half of the new month, at least, looks good for cold and some natural snow roughly north of I-80 from the Midwest into the Northeast. It won’t be long now.

Herb Stevens

The Skiing Weatherman: How Do Pacific Cyclones Dictate US Weather?

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The Typhoon Rule Can Predict Chilly Wet Air In North America.

In an age where computer models are believed to be the only viable long range weather forecasting tool, there remains a very effective technique for looking ahead a couple of weeks that had its roots in World War Two. 

It is called the “Typhoon Rule”. When the far western Pacific is active in terms of tropical disturbances, it is a great way to determine what the jet stream pattern will look like over the US with a lead time of one to two weeks. 

Military forecasters in the Pacific theatre dealt with typhoons pretty much year round, due to the persistence of water warm enough to form and sustain such storms in that part of the ocean.  One of the meteorologists noted that after a typhoon either re-curved over or east of Japan or tracked straight west into mainland Asia, a change in the weather would result in a week or two in Washington, D.C. and thus the correlations were born.  Here is how the Typhoon Rule works:

All tropical disturbances across the globe act like a cork in a stream.  They are warm systems without the warm and cold fronts that drive mid-latitude low pressure systems, and are therefore more influenced by jet stream level winds in terms of where they will move.  When a typhoon in the southwest Pacific encounters an upper ridge to the north—centered over Korea and Japan—the clockwise circulation around the ridge directs the storm westward, often through the Philippines and into Asia. 

A ridge in that position correlates with an upper level ridge and tranquil weather over central and eastern North America with a lead time of one to two weeks.  However, when the axis of the Pacific ridge is set up further east by several hundred miles or more, over the waters well east of Japan, the typhoons tend to run around the perimeter of the circulation, leading to a track that heads for Japan before turning north and then northeastward. 

This happens in a fashion similar to Atlantic storms threatening the east coast before turning around the perimeter of the Bermuda high as they head for New England and the Maritimes—when the ridge is far enough to the east, the storms miss the U.S.  A re-curving Pacific typhoon around a ridge well east of Japan correlates with a central/eastern North American trough, often leading to colder and stormy weather.

As we wait anxiously for the new season to start, the Typhoon Rule can give us a hint as to when colder air masses will be available for early season snowmaking or natural snow.  As I write this on Oct. 22, the Typhoon Rule is set up for a cold air mass to dive into the center of the country later in the week of the 28th.  The cold will also spread into the East, though in modified form.  Take a look:

This October typhoon is re-curving to the north east, transporting its heat to a trough in the Gulf of Alaska. Result: an early cold shot that will get snow guns going.

There are nuances to the rule, and one of them comes into play here.  This strong October 22 storm will not make a dramatic turn to the northeast toward the Aleutians, but it will turn north of east. This track suggests that the trough/cold shot will be centered in the middle of the country with the chilly air eventually spreading east. 

The Killington Women’s World Cup is about five weeks away, and it looks as though the snowmakers will be able to get started there around Halloween. The Typhoon Rule that an observant WWII forecaster discovered says so.