Foggy Bottoms

Posted by Rufus La Lone on

Monday January 24
Foggy Bottoms will be the rule for much of the next 6 days.  Keep your hands warm on that Mug.
A stagnant air pattern - with colder air trapped at the surface, capped by a relatively warmer air layer above - will be in play most of this week.  Areas of afternoon clearing will be spotty - in the usual places.  By Thu Jan 27 a high pressure ridge centered over ID may initiate enough easterly offshore flow to clear out the persistent fog, and help ‘clean the stagnant air’ for a day or two, and yield to a bit more sunshine.  By Sat, the fog may return until a weak system ushers in the first round of change - a return to a more active weather pattern typical for February. 
It will turn colder, but beforehand, expect that weak system to arrive - from north to south - sometime on Sunday Jan 30.  Showers possible over western OR & WA, as a cold-core Low pressure trough positions over OR by Monday night.  A cold rain or rain/snow mixed showers will fall, snow showers likely below the passes & maybe the coast range under this 1st cold air trough.  That Low will continue south into CA, setting up a stormy, wet pattern for much of CA, including snow down to rather low elevations for the Golden State.   
For the PNW, expect temps to be colder with a push of modified Arctic air out of the Fraser Gap by Wed Groundhog Day.  WINDS will be strong, but not damaging, as the barometric pressure differences are charting to be less severe than our last report.  Still, it will be the coldest pattern since December, so any moisture that arrives over the north Puget Sound could fall as snow, or rain/snow mix.  For this first clip of coldness, the bulk of the Arctic air will travel east of the Rockies.  Cold nights, with icy fog possible for Tue and Wed Feb 2,3.
Second round is due to arrive beginning on Fri Feb 4. Admittedly, this round is ‘way out there’ on the charts, so accuracy can be challenged, however, we have been monitoring this pattern on the charts for several days now, which raises the certainty a bit higher.  Anyway, Fri night Feb 4 charts with a modified Arctic air mass dropping into the eastern basins of OR, WA and a notable renewal of outflow from the Fraser Gap in NW WA & BC.  There should be enough moisture around to introduce some snow flurries or rain/snow mixed showers overnight into Sat Feb 5 west side.  After the cold air arrives, it will turn dry and cold, with a chilly wind from the E-to-NE.  Temps will be below freezing at night (possible mid-20s west side).  This dry pattern may hold from Sunday Feb 6 through Wed Feb 9.  There are a couple model solutions bringing more rain, wind and LOTS of mountain snow into the PNW by Tue Feb 8.  We’ll see which scenario is likely in future reports.
Bottom line: the PNW will on the edge of a cold outbreak as we head into February.  The coldest portion may remain far to the east, but we see enough model solutions indicating that cold may clip the PNW to warrant mention here.  In the meantime, foggy bottoms will dominate.
“If we wait until we've satisfied all the uncertainties, it may be too late.” -Lee Iacocca
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