Winter-like Pattern

Posted by Rufus La Lone on

Friday November 4
Are you ready?  Hold your warm Mug tightly.  A winter pattern is about to arrive, as is heavy rainfall & strong winds. 
Today through early Saturday expect rain to be steady & heavy.  While pinpointing the exact area the ‘jet stream’ will focus on may be challenging, the powerful mid-level winds will trigger major rainfall totals for a large swath of the PNW west of the Cascades.  Initially, the freezing level will also be high (~7,000 ft), which means much of that moisture early on in this event will NOT be held up in the mountains as snow.  Streams/Rivers will rise rapidly.  Localized flooding will be an issue.  Heed Nat’l Wx Service watches/warnings.  Furthermore, WIND today and this evening will be strong enough to topple trees or break limbs (many still holding ’sails’ - leaves), so power issues are probable.  A short break in the action is on tap for late Saturday, but by Sunday, another WET and COLDER system will drape over the PNW, adding to high water issues.  
COLD.  As the Sunday storm front passes, the coldest air of the season will flow in behind.  This will be enforced by a Yukon High pressure dome (modeled in the 1045-1050 mb range) which will shift south, setting up STRONG WINDS out of the Fraser River Gap first, then down the Columbia Gorge early next week.  Spokane will also experience powerful winds Mon & Tue.  Temperatures will be cold enough for SNOW down to very low elevations, if not the valley floor, if there is moisture in the area.  For now, the models track most of the moisture south into California following the Sunday front.  However, moisture spinning northeast from the Sunday Low (that will position itself just off the coast of southern OR), may present snow/rain mixed at the surface under showers that will form over western OR; accumulations not expected below 1,000 ft., as the ground will be rather warm.  That said, we will experience overnight subfreezing temperatures, esp in wind sheltered areas, once the air dry down on Tue.   Expect mid-20s overnight Tue & Wed, Nov 8,9.  HARD FROST.
The east to NE winds should diminish by Wed afternoon for all areas.  Temperatures will slowly moderate; fog may form late week.  Right now, the models are holding any moisture from another storm well off the coast for a few days.  That means the Friday threat for freezing rain in the Columbia Gorge is low.  Should the system track closer to OR, as was projected a couple days ago, frozen precip would be an issue.  
The weekend of Nov 12,13 is trending relatively dry, with an east-to-NE wind picking up just a bit, limiting fog formation.  The dry pattern may hold through Wed Nov 16, before systems slowly work their way closer & closer to the PNW from the west as the week ends.  Stormy conditions may return after Thu Nov 17.  
Overall, an early winter-like pattern is developing for the PNW.  We always monitor High pressure over the Yukon area as a precursor to cold snaps in the region.  The “Yukon Dome” expected next week is quite early.  If not already done, winterize irrigation/plumbing systems before Tue.  The short break late Sat may give you a muddy chance.  
A quip from the ’Net:  “My new SUV has a button that says, ‘Rear Wiper’.  I’m afraid to push it."
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