A Lesser Extent

Posted by Rufus La Lone on

Friday December 16
As Elvis once sang, “I’m all shook up!”, so too are those of us trying to formulate weather reports out of the ever-changing computer model outputs.  Let’s try again, shall we?
The position of the anticipated modified-Arctic air mass is being adjusted by the models; meaning, we are less likely to have a huge winter event over the next week.  Still, there will be some surface snow & the potential for sleet and/or freezing rain in places.  As alluded to, the key is the ‘depth’ and position of the Arctic air as it moves south into the US.  The first round is following projections closely, so expect precipitation to fall as snow down to the surface, and esp 500-1,000 ft starting in far NW WA overnight tomorrow, Saturday; light snow is possible (1/2" - 1.5”) around Bellingham north; same for many locations in the Puget Sound by mid-day Sunday.  How far south the snow threat goes will depend on the movement of the cold front.  We do not have super-cold air east of the Cascades, and thus a cold outflow to the west will be minimal in the first round.  The moisture may not extend as far south as Salem.
On Monday, modified-Arctic air will continue to seep into eastern basins; wind will be strong out of the Fraser Gap - and a weaker wind in the Columbia Gorge - adding to the cold air pooling west side in WA; to a lesser extent in NW OR.  Another Low will track south along the BC coast before moving onshore in north Vancouver Island.  This is much farther north that we expected in earlier reports; which equates to rain at the surface because of southerly breezes, although snow is possible over NW WA as the moisture begins to arrive.  For most of western WA and nearly all of OR can expect plain rain.  The Gorge could have frozen precip issues early on.
The coldest pool of that 2nd shot Arctic air will track east of the Rockies, missing the PNW, which is why the next PNW system on Thu & Fri will be RAIN and not the heavy snow and icy conditions we were concerned about a few days ago.  The forecast is “all shook up”, indeed.  Anyway, best news is that holiday travel should proceed under normal PNW conditions, easing frustrations during an already hectic week.  
Christmas Weekend:  another favorable ’turn’ in the forecast — it now looks dry, with a bit of a chilly NE wind.  Ho Ho Ho.
Post Christmas - well, if we are to believe the current chart pattern, warmer temps, VERY WET weather following Christmas on into the next holiday.  Moderate-to-heavy rain is possible, with cooler temsp and lots of mountain snow for skiers probable by week’s end.  It should be rather blustery, as well.
Bottom line: we may have missed a major winter mess during a critical travel period.  Keep alert, as all of this is variable. 
“You cannot do a kindness too soon because you never know how soon it will be too late.” - Ralph Waldo Emerson
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