On the Cold Side

Posted by Rufus La Lone on

Friday December 10

Lots of impactful weather on the way.  Mug up.
A large pool of cold air, that we have been discussing here, is beginning to settle in over the eastern Pacific / Gulf of Alaska.  The resulting broad Low pressure trough will spawn several surface Lows over the next several days, most of which will track south towards CA and southern OR.  But first, a powerful storm will arrive this weekend.  WIND will be strong - steady at 35-45 mph in places, esp over western WA, 25-35 mph over western OR.  Gusts, both regions, will likely top 45-50+ mph - meaning power outages are probable.  Plan ahead, Patron!  Rain will be heavy, with anywhere from 1.5” - 3” possible in the lowlands between now and Monday afternoon.  SNOW in the mountains will be measured by the FEET.  A range of 2 ft - 6 ft of snow is being forecast, depending on elevation.  For Patrons traveling over the passes, beware, this is NOT a joke - have winter gear with you at all times.
Next week will remain on the damp side, with occasional low elevation snow (500-1,000 ft) or mixed snow/rain at the surface, esp north of Seattle.  More snow in the mountains.  Wed, Thu and/or Fri Dec 15-17 mornings could be ICY, if the sky clears in your area.  Do not rule out surface snow in the Bellingham/Lynden/Abbotsford areas anytime between thisSunday and the end of next week, as a weak outflow from the Fraser River Gap could enhance that chance.
Mixed chance for cold showers and dry conditions for the weekend of Dec 18,19.  It will continue on the cold side.  Models have differed on the solution for Christmas week, but for now, expect conditions to remain chilly, and maybe even turn colder because of increasing COLD outflow through the Gaps (Fraser & Columbia Rivers).  Another large cold air mass will reform over the eastern Pacific, setting up increase in offshore winds at the same time as Pacific moisture rolls in — yes, the classic set up for snow and/or freezing rain.  Either way, it looks WET most of that week.  Note that some solutions place a Low pressure cell just off the coast of WA, along with a dramatic pressure difference because of COLD High pressure over inland BC.  NW WA Patrons know the drill — strong outflow, freezing temps and moisture. 
Christmas Eve / Day:  trend is for chilly-to-cold weather to continue and for the chance for SNOW for NW WA & BC (see above).  For SW WA, OR and portions of northern CA, very wet period on Christmas Eve; damp Christmas Day.  Snow level around 1,500-2,500 ft.   Hood River area may have frozen precip issues.  Any mountain travel will require chains/snow tires.
In Summary: lots of rain, wind and feet of mountain snow on the way for all of the PNW; the chance for periods of surface snow or a rain/snow mix cannot be ruled out, esp for Patrons in the far NW corner of the region.  Yep, December.
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