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The Skiing Weatherman 2/18   Pattern in flux means some snow for much of the U.S.

Since my last posting, I have only managed a couple of days on snow.  One at Sugarloaf after an 8 inch overnight and then a brisk day at Killington earlier this week on some of that cold, styrofoam that the NBC announcers have been referring to in the Olympic alpine events.  After a superb tuning at the outstanding shop at West Mountain in Glens Falls, New York the day before, that stiff snow at Killington was very playable.

As I look down the road at the evolving weather pattern to close out February and start March, I see a changeable landscape.  After a dominant western ridge/eastern trough couplet from mid-January until just recently, the pattern will be more changeable for the next week to ten days, but signs point to a return to the trough favoring the eastern half of the country early next month.  The changeable nature of things will allow a meaningful snowfall to impact much of the west later this weekend into early next week, as suggested by this jet stream map for President’s Day…

With a ridge poking up into Alaska, very cold air will flow into the western trough and while this doesn’t look like a blockbuster due to the lack of a direct influx of deep Pacific moisture, it should generate moderate to heavy amounts from the Cascades all the way down to the southern Rockies as it slowly pivots southeast and then east Sunday through Wednesday.  With the core of the trough heading down the spine of the central and southern Rockies, the Sierra will pick up light to moderate amounts south to around Tahoe from this system.

In the eastern half of the country, milder air will spread north in advance of the western trough, but not until after a seasonably cold holiday weekend.  By late next week, the trough will start to favor the Midwest and East, a development tipped off by the trend of both the WPO (Western Pacific Oscillation) and EPO (Eastern Pacific Oscillation).  These two indices are based on the relative positions of upper air troughs and ridges over the waters of the north Pacific.  Here is an illustration of a negative WPO…  

The orange indicates an upper air ridge, and the blue areas an upper trough.  The clockwise circulation around the ridge helps to access cold air from the northwestern corner of the continent. It works in tandem with a downstream trough, as suggested by the pale blue over the center of the country.  A negative EPO is similar.  Here is a forecast for the WPO for the next couple of weeks…

The green line is the one to follow and after running in positive territory, which infers a trough over the northern Pacific waters, it switches to negative around the 1st of March, at which time I think we will see a trough start to strengthen over the eastern half of the country while a ridge returns to the West.  Colder air will populate that trough, and the first part of next month should turn stormy over the Midwest and East.  With the WPO remaining in negative territory well into March, the prospects are solid for late-season snow.  In my next installment, I will explain why March could bring snowy weather to the East AND the West.

Regional details…         

Northwest U.S./Western Canada:  Nice shot of snow late this weekend/early next week.  Next event about a week later.    

Sierra:  Late weekend light to moderate snow…another round next weekend.

Rockies:  Moderate snowfall early next week into midweek.  Next potential snowfall about 5 days later.

Midwest:  Fresh snowfall early next week.  Pattern remains loaded with potential snowfalls for the foreseeable future.    

Mid Atlantic/Southeast:  Mid Atlantic snow on the table for late next week.  Southeast chances enhanced in early March. 

Northeast/QB:  Clipper snow this weekend in the Northeast.  Late next week looks quite promising for more substantial snowfall.  March shaping up nicely. 

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