New Year…New weather pattern…

The 2021 holiday period provided epic snow conditions across most of the West with trails counts and surface conditions rather sketchy over the eastern half of the country.  While storm after storm nailed the West, a typical La Nina upper level ridge over the southeastern states was enhanced by a sudden spike in the output of the sun, as detailed last week.  The solar flux increase has reversed course in dramatic fashion as the red line on the following graph shows…

With the change in the solar flux, that pesky southeastern ridge has been crushed and replaced by a skier friendly upper trough as illustrated on this map…

That trough has delivered two snowfalls to the Mid-Atlantic and parts of the Northeast this week and troughs will be the dominant jet stream feature over the eastern half of the U.S. for the next several weeks.  The northwesterly flow across the Great Lakes will deliver cold air masses that will support major snowmaking efforts, as well as natural snow at times.  One source of natural snow will be “Alberta Clippers”…smaller scale troughs that originate in west-central Canada before tracking through the Great Lakes and into the larger jet stream feature further east.  Mid-winter Clippers produce fluffy snow north of their centers and usually bring along a reinforcing shot of cold air with them.  After a mild autumn and early winter, the waters of the Great Lakes are still warmer than normal, so meaningful lake effect snow can still fall although we are approaching midwinter.  Lake effect has helped boost trail counts and soften surface conditions in the Midwest during the past week and that trend will continue.  Clippers can turn into something more formidable as they approach the east coast if a smaller scale trough also comes rolling along in the southern branch of the jet stream.  If the two streams phase, which strengthens the trough, very often the result is a bonafide Nor’easter.    

I don’t want to forget the West, but the parade of storms that pounded that half of the country for the final three weeks of December has slowed down considerably, and with an upper ridge axis just off the west coast for much of the time in the next 2-3 weeks, the amount of moisture that reaches the Cascades, Sierra, and Rockies will be much more limited.  Systems will crest the top of the ridge and spin down through B.C., the Northwest, and the northern Rockies at times, but they will be weaker than their December cousins.  The southern branch of the jet looks to be more active later next week, so the southern Sierra and Southwest resorts could be in line for a refresher event at that time.  As long as the trough dominates in the East, though, there will be more bluebird days than powder days out west.    

Looking further down the road, here is a jet stream forecast for the 21st that looks good to me…

The clockwise flow around the ridge over the northeast Pacific will deliver arctic air to the trough covering the eastern two thirds of the country, sustaining the winter weather that is now locking in.  By this time, conditions coast to coast should be outstanding.

Here are regional highlights…    

Northwest U.S./Western Canada:  This week ends with one more heavy snowfall.  Weaker systems move through with light snow next week.            

Sierra:  Development of upper ridge stops the storm parade for the next week and likely beyond.  Southernmost resorts could pick up new snow late next week.             

Rockies:  Upper ridge dominates going forward.  Bluebird skies common…snowfall harder to come by. 

Midwest:  Winter has locked in.  Lake effect, clipper snows and virtually unlimited snowmaking windows continue. 

Mid Atlantic/Southeast:  Two snowfalls in the past week have helped.  Favorable pattern continues in place much of this month.          

Northeast/QB:  Cold dominates this month.  Presence of upper trough will pick up the pace of natural snow.    

One Comment

  1. Bob Bowlby says:

    Herb tell us about your favourite resorts in Switzerland please.

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