Winter Conditions All Around

Lots of weather action on the way for the next several days.  And, there remains plenty of variance in model projections as to whether or not snow reaches the surface or remains above 500-1,000 ft later this week.  Let’s take a look.  Mug time.

Rain has begun.  Today (Monday) will be damp, with increasing WIND & RAIN intensity overnight into Tue.  A large, deep Low is moving onshore north of Vancouver Island, but it is so deep (visualize a large bowl with the center north of Vancouver Is.) that the WIND FIELD from the storm will impact western OR & WA.  Gusts are likely to exceed 50 mph, esp around the Puget Sound region (& coast, of course).  Simultaneously, freezing levels will drop fast, ushering in a MAJOR BLIZZARD situation across the WA & OR Cascades.  Nat’l Wx Service personnel have posted several warnings about this situation.  Stay out of the mountains for a few days.  Snow will be measured by the feet; wind gusts to exceed 60 mph.  Visibility - don’t even think about it.  Coastal flooding is a concern, as king tides will be ‘magnified’ by the strong onshore winds.

Tue & Wed Jan 9,10: a secondary smaller system is modeled to come onshore somewhere around Astoria late Tue evening.  Areas north of that Low may get snowfall down to the surface, or very near so.  (We should note that this smaller Low may not even develop.)  Expect less rain on Wed, with colder temps and the chance for rain or snow showers around the entire region.  Similar for Thu, except that Arctic air will begin to rush through the Fraser Gap - dropping temps even more across northern WA and BC.  Snow showers possible all day into Fri during this Gap outflow.  Western OR & SW WA should see rain/snow showers, but the air mass may remain warm enough at the surface to limit any snowfall.  

As the modified Arctic air mass settles farther south & east, the eastern basins of WA & OR, as well as ID, will continue to chill down.  The bulk of the super cold air will remain east of the Rockies (per the latest model solutions).  A warm front will move onshore Fri night or early Sat morning - this will set off the chance for snow, freezing rain, or rain, depending on 1) how much cold air fills into the eastern Columbian basin and central OR to flow out of the Columbia Gorge or down the Cascade passes in WA; 2) southern surface winds.  Right now, the greatest threat for frozen precip looks to be over NW WA and maybe Portland area.  The precise center of that Fri night Low will be key.  Stay tuned to local forecasts, as this situation will not be static, with small positional changes having a big impact.

The weekend of Jan 13,14 looks mixed.  Snow, freezing rain or rain.  The Low mentioned above may become stationary west of Astoria and fill in without crossing the state.  Cold air to the east will be drawn west, so hence the mix of frozen precip depending on your location.  The Fraser Gap winds will lessen, but remain present, adding cold air to the ‘pool’ in place from earlier.  Remember though, the coldest portion of this event may remain east of the Rockies, and not be so severe as to keep the west side in a snow plane.  Snow in the Tri-Cities & the rest of the Cascades.

The air mass should warm slowly over the weekend into the early part of the Jan 15-19 period.  Another strong storm system is charting to develop and move south along the BC coast on Tue Jan 16, but this time it is charted to “bump into” a warmer air mass moving in from the west/southwest.  Result: moderate-to-heavy surface rain - first over western WA, then shifting south into OR by Wed.  WINDY.  We do not see a repeat of a cold Yukon air mass pushing through the Fraser Gap, as the Low will track north of the border.

Heavy rain may develop by Fri Jan 19 and last until early Sat Jan 20.  Oregon to get the brunt of this deluge.  It could be mostly dry Sunday and Mon, Jan 21,22, then turn wet again for western WA for a couple of days; OR may dry down.  Temps will be mild during this period.

Again, lots of uncertainty.  Best to be prepared for winter conditions.  As we said the other day, getting in & out of the PNW by road will be a “whitemare” - blowing snow everywhere higher than 1,000 feet.