December 01, 2023

Strong Winds and Heavy Mountain Snows Coming to the Pacific Northwest

After a period of high pressure, weak winds, fog, low clouds, and little precipitation, the weather in our region is about to get quite intense and interesting.

Strong winds will soon buffet western Washington and heavy snow (multiple feet) will fall across our regional mountains.

A front went through this morning and our region is now in moist, unstable northwesterly flow as shown by the visible satellite image this morning (below).  The white and dark areas offshore are convective showers and you can see the intense cloudiness on the western slopes of the Cascade associated with substantial snow showers.

White-out conditions are now occurring in the mountain passes, illustrated by the WSDOT pass cam below.


Let me show you predicted snow accumulations from the latest University of Washington model forecast.

Through 4 PM the Cascades will get as much as 6-12 inches, and eastern Washington be whitened.

The total through 4 AM Saturday is much more impressive, with 1-2 feet over higher terrain.


And by 4 PM Saturday, many locations will have experienced 2-3 feet.  Substantial snow will fall over northeast Washington and northern Idaho.


The snow season will begin with a bang and many ski areas should be able to open.  Travel across the passes should be dicey during the next day...so keep that in mind.

The regional snowpack had declined to about 50% of normal.  By Sunday, we should be at or above normal levels in most locations.  I should note that other modeling systems (such as the European Center) agree with this forecast.

And then there are the winds.....

 Some of you will experience power outages overnight.  I am charging up my devices as soon as I get home from the UW!

A low-pressure system will move eastward to our north, creating a large north-south pressure difference across western Washington (see forecast surface pressure map for 4 AM Saturday).  That means strong winds.

The latest NOAA HRRR forecast (available on the City of Seattle Windwatch site built by the UW) predicts powerful winds overnight. 

 Below are the forecast gusts at 1 and 3 AM.  First, the coast and NW Washington will get hit and then Puget Sound, some with winds exceeding 50 mph.  Such winds guarantee some power outages.

The only good thing is that many trees have lost their leaves, making them less vulnerable


Considerably more active weather is predicted beyond this weekend, including heavy rain and potential flooding, including a major flood on the Snoqualmie River (see the NW River Forecast Center plot below).  


I will talk about that threat in a future blog......one major weather challenge at a time!


9 comments:

  1. So, yes, reviewing your forecast, it appears that we will have a notable amount of snowfall in our upper watersheds. But if I understand your forecast data predictions that appears to suggest we're probably going to lose most of that, with the exception of the snow above 6,500 to 7,000 feet. Is that accurate? Also, professor, I note that Anchorage is having a possible record November, going into December snow season. Is that by your data a consequence of El Nino? Say, the adverse of what will happen in the West Coast mountains in the lower 48, south of the British Columbia Coast Range? Thanks. Looking forward to your next post on the current weather situation.

    ReplyDelete
    Replies
    1. That's what I am seeing. On mountain forecast the freezing levels are very high on Sunday night; around 10k feet on Rainier with snow levels a bit lower. The amount of rain predicted is nuts too.

      If that materializes it's going to be a mess. Here's to hoping the forecasts are overestimating temperatures

      Delete
  2. Hopefully the winds will blow the leaves out of my yard and into someone else.

    ReplyDelete
  3. Are strong gap windows expected in the foothills near the passes, or is this primarily a coastal wind event?

    ReplyDelete
  4. The storm before the El Nino calm this winter so lets enjoy the moment.

    ReplyDelete
  5. For me, just north of EBRG, a little snow, a little rain, non-serious wind Sat Noon, and then rising temperatures (rain).
    Executive Summary: "crummy weather"

    ReplyDelete
  6. The current forecast for snow was (surprisingly) spot-on here in the valley northwest of Mt Baker (Glacier). "Oh by gosh, by golly" ...here we go! Keeping the home fires burning; there's actually been a tad more than we expected at this low elevation. The ski area may open end of next week - they're hopeful. I've seen far worse starts to the season. Cheers!

    ReplyDelete
  7. In southern Thurston County, it was hardly windy at all that night. It maxed out here at only 13MPH.
    At the peak of the power outages mostly centered on Tacoma and Seattle, dozens of them with almost 9000 outages, most were fixed in less than 24 hours. I've been impressed with PSEs repair capacity in the last few years.

    ReplyDelete
  8. In western WA, what months have historically had the worst floods?

    ReplyDelete

Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

How unusual is it for aircraft to exceed the speed of sound?

Announcement:  Doing an online zoom session with Patreon supporters at 10 AM tomorrow (Saturday) ______________________________________ The ...