Snow For All.

Often when I write this piece, I have good news for one region of the country and not-so good news for other areas of ski country. Such is the nature of winter weather across a country that stretches 3,000 miles from coast to coast and with so many and varied climate zones. However, just as there are times in the middle of the summer when much of the country is warmer than normal, occasionally we see a pattern in winter where most or all of the skiing regions get lined up for significant snowfall at roughly the same time. We are entering just such a period.

In order for a favorable pattern to set up for such a large area of the country we obviously need an ample supply of cold air. From mid-December until just recently, most of the air flowing across the country was of Pacific origin, not the prime source region for winter weather. The jet stream configuration now in place is tapping cold air from the northwestern corner of the continent. There is still a risk that we could see an intrusion of severely cold arctic air by the end of the month, but at a minimum, enough cold has showed up to make even southern regions cold enough to be on the lookout for fresh snow. It certainly helps that this is the time of year when normal temps in most areas are right at their climatological minimums for the year. To illustrate the extent of the cold air, here is a look at the forecasted 5,000 foot level for Friday, Jan. 29^th

The area shaded in hues of blue indicate where temps will be below freezing. Sub-freezing temps at that level are a proxy for where the column of air overhead is cold enough to support snow, even the southern Appalachians look sufficiently cold.

The other ingredient for widespread snow is a favorable jet stream configuration. Here is a forecast for the jet stream for late next week that I agree with, showing three key components to a snowy pattern from coast to coast.

The trough along the west coast will produce fresh snow from Alaska down to the southern Sierra, and inland to AZ and NM as well. Storms from the southern end of that trough will traverse the country and bring the opportunity for snow to the central and southern Appalachians. The red ridge over northeastern Canada will remain in place and help keep storms from cutting through the Great Lakes, which would produce rain to the east of the track. Northern disturbances will come out of the Gulf of Alaska, move along the U.S./Canadian border, and produce snow in the Great Lakes and Northeast from time to time. Those systems are often called Alberta Clippers because they typically move through that province. If the impulses in the northern and southern branches of the jet combine forces, the trough off the east coast will be pulled westward and potentially lead to a blockbuster coastal storm for the mid-Atlantic and Northeast. The potential is high nationwide. Let’s hope the pattern delivers the goods!!!

Regional Details

Northwest U.S./Western Canada: The trough along the coast produces multiple rounds of meaningful snow over the next couple of weeks. No issues with snow levels due to input of arctic air.

Sierra: Trough extends far enough south to produce a much more active storm pattern to this region.

Rockies: Full length of the mountain range will have frequent snow events into early February.

Midwest: Clipper systems keep coming every two-three days into next month. Each one will produce light snow with backside lake effect, as well.

Mid Atlantic/Southeast:  Cold enough for snowmaking; southern storm track could generate natural snow at times.

Northeast/QB: Clipper systems help northern resorts with light snow at times. Ridge over Canada likely to suppress major storm track too much UNLESS two jet branches combine for coastal storm.

The Vortex Is Coming.

Last week I discussed a major pattern change that would unfold over North America this month. As we hit the midpoint of January, those changes are well underway. An episode of stratospheric warming over the far northern reaches of the hemisphere has matured in typical fashion, leading to the displacement of the polar vortex away from the North Pole. One chunk of the vortex’ cold air has descended into Asia, with another pushing into Europe, causing a 20 inch snowfall in Madrid! North America is next in line as the jet stream reshapes itself and changes the prime source region of air for the U.S. from the Pacific to the Yukon and Arctic regions. Here is the current jet stream set up…

If you start in the eastern Pacific and head inland you will see that all the way from British Columbia to the Baja, the air flowing onto the continent is of Pacific origin. Maritime air masses can be cold across the far north, but overall, they are not friends of winter sports. Yes, they provide moisture but the relative warmth of the underlying body of water ensures that their chill is limited. This is the configuration that has dominated for several weeks and while the high elevations of the West have been able to convert most of the moisture to snow, further East, each storm of late has been battle for every snowflake. The deep trough that you see over the Midwest on this map has just enough cold air directed into its’ circulation from the north to promise some fresh snow this weekend from the northern Great Lakes eastward to New York and much of New England. Due to the presence of the blocking ridge over Quebec and Labrador, this system will linger into next week, leading to additional accumulations over the mountains of the Northeast.

Next week, a series of additional troughs will spin out of the trough over Alaska, crest the ridge that is building in western Canada, and track southeastward through the Lakes and into the East. One of those systems will split, with one piece continuing southeastward and another piece turning into the Southwest. Each successive disturbance will bring with it increasingly cold air masses. By the time we reach the 23^rd or so, the jet stream pattern will look something like this:

Now, if you start on the peak of the ridge north of Alaska and head south, you will see that the prime source region will be very different, and potentially very cold. With a trough covering much of the country AND with plenty of cold air involved, we will enter a stretch of weather when snows are frequent. The block over northeastern Canada will help to suppress the storm track enough so that the risk of lows that cut through the Great Lakes and bring mixed precip/rain to the Northeast will be limited. With the possible exception of the southern Appalachians, where the ridge over Cuba will push milder air northward, we are heading toward a pattern favorable for snow nationwide. Bring it!

Regional Details

Northwest U.S./Western Canada: Parade of storms resumes late next week as ridge axis eases offshore.

Sierra: West coast ridge keeps it mild and dry for a week. As ridge axis moves offshore, snow prospects improve late month.

Rockies: Northern resorts pick up fresh snow every few days. Fresh snow for central and southern resorts as upper air disturbance settles/develops over region.

Midwest: Pattern turns progressively colder and Clipper systems bring snow every few days. Lake effect snow supplements the Clippers.

Mid Atlantic/Southeast:  Northern resorts benefit from colder, snowier pattern. SW Atlantic ridge turns ii milder in southern Appalachians.

Northeast/QB: Weekend storm brings meaningful mountain snow. Pattern turns colder late next week, likely with new snow threat. Great conditions a solid bet by late month.

The Busy Pattern Continues.

Last week’s installment headlined a progressive pattern that has been sending ridges and troughs west to east across the continent at a dizzying pace.  That pattern produced some meaningful snow in the West earlier this week and then unloaded a blockbuster on the mid-Atlantic and much of the Northeast midweek, jumpstarting the season at dozens of resorts in the East as a result.  The heavy snow did not extend to far northern New England, but snowmaking temps have been in place all this week so trail counts are on the rise.

For the foreseeable future, the fast moving pattern will continue with a tendency for upper level troughs to spend more time in the East then they did earlier in the season.  Why the change?  It has a lot to do with the phase of the NAO, or North Atlantic Oscillation.  When the NAO is negative, we typically see an upper level ridge over Greenland and the waters to the south.  In that position, it tends to slow down troughs as they move into eastern North America, giving them a chance to strengthen, spawn surface lows near the coast, and tap more in the way of cold air from Canada.  That scenario unfolded this week during the current Nor’easter, and another storm could be in the cards again around Christmas Day.  Here is a jet stream forecast for Christmas night that illustrates a classic negative NAO.

Christmas Day Jet Stream snapshot.

Prior to the arrival of the trough you see in the East, it will bring some snow to the upper Midwest on Christmas Eve, but in that position, a milder southwesterly flow will be in place further east.  We could see one storm cut up through the Lakes, with a second storm then forming along the coast as the trough (and its cold air) tracks eastward.  That could result in a rain to snow sequence playing out in the East on Christmas Day.  Cold air will flow then into the Midwest and East early in the holiday week as the NAO will remain negative.

In the West, most of the action will continue to be focused in WA, OR, and BC, where shorter wavelength troughs keep rolling in from the Pacific Ocean.  This weekend will bring a juicy system that originates further south, so it will lead to higher snow levels in the Cascades—as high as six-seven thousand feet.  Snow levels will drop later Sunday into midweek, however, with fresh snow continuing through that period.  Further inland, lighter snows will be common for the first half of next week in ID, MT, and WY.  South of there, fresh snow will be scarce next week due to the presence of a flat ridge that doesn’t want to give way to systems from the north.  Now, if you take a look at the jet stream map again, you will notice a large blue blob just off the west coast around Christmas Day.  That trough will likely move toward the coast and perhaps bodily move inland early in the holiday week.  That could turn into a very productive storm across a wide swath of the West.  So, COVID restrictions aside, the holiday period is starting to shape up. Better late than never.

Regional Details

Northwest U.S./Western Canada:  Plenty of snow in the next week, but with bouncing snow levels in the Cascades.  A snowy, colder trough arrives just after Christmas.

Sierra:  A quiet week leading up to Christmas. Prospects for snow improve after that.     

Rockies:  Light to moderate snows across the north leading up to the holiday keep surfaces soft and boost trail counts.  Central and southern resorts waiting for the post-Christmas trough.       

Midwest:  Light snow early next week, more significant snow looking good for Christmas Eve.  Good snowmaking temps much of the time.

Mid Atlantic/Southeast:   Nice weekend on the slopes after fresh midweek snow.  Milder next week.  Colder after Christmas.    

Northeast/QB:  Quiet until Christmas storm that brings rain to snow.  Wintry pattern during holiday week.