Thursday, November 14, 2013

Heavy Snow in the Mountains and Arctic Air Teases the Northwest

When will skiing begin in the Washington Cascades?  Is there a possibility for Thanksgiving skiing, at least on the cross country trails? 

You need to start the season with a good base, and during the next 48h the Cascades will get a nice 1-2 foot dump of powder.  Enough to make those folks in Utah and Colorado a bit envious.   And some cold Arctic air will push south into British Columbia, with some leakage flowing down the Fraser; perhaps, giving Bellingham and San Juan's a small taste of the cool, northeasterly flow that sets the flags waving at the Bell Faire Mall there.  

The fun will be associated with a trough moving southeastward along the eastern flanks of a huge ridge in the eastern Pacific (see graphic)
This trough is embedded in quite strong northwesterly flow.   A good pattern for snow around here...you get some precipitation but temperatures are cool enough for snow from pass levels to the Cascade crest.  

And now the exciting part.  Here is the predicted 48-h snowfall ending 4 AM on Sunday from the UW WRF model.  A lot of the Cascades will get 1-2 feet of snow if this is right.  Some higher elevations even more.   And this will not be any snow.  Decent powder.
The other interesting thing about this event is that quite cold air will be getting into British Columbia.  Take a look at the predicted surface air temperatures for Sunday at 7 AM.  You see those purples and whites?  Temperatures in the teens and below.  Not that far away!


As the trough moves through on Saturday, there will be a strong surge of westerly winds in the Strait of  Juan de Fuca and powerful northwesterlies down the Strait of Georgia (see graphic showing surface gusts  at  10 PM Friday evening).  50 kt winds approaching Whidbey!  And strong winds in the Cascades.   Be very careful if you are planning to cross a Cascade pass...it will be treacherous and dangerous.


And then by Saturday afternoon, modest northeasterlies coming out of the Fraser....a relatively weak case though (see figure). Still windy in the Strait of Juan de Fuca and in the Cascades.

But I have bad news for snow lovers.  By Tuesday, a warm, wet system will approach our coast (see map).  Freezing levels will move above the passes and rain will fall on the beloved powder.  Well, we like a nice Cascade concrete layer as a base....I guess.





5 comments:

NateLMP said...

Hey Cliff, I noticed per the intellicast.com pacific satellite imagery that there is something cooking up down in the tropics towards Hawaii. Perhaps that is what you are referring to when you are predicting a "warm wet system on Tuesday. I also noticed the jet stream has taken a dip down into California per the SFSU jetstream analysis. Is that thing looking like it may be a potential "atmospheric river" event? Is it likely to miss us if the jetstrem doesn't creep back up in our direction? What are the main ingredients necessary for an AR? Thanks for your dedication to this field.

-nate in ne seattle.

David Britton said...

Great news! I am surprised to see winter storm warnings hoisted for cascades and not even a watch for the olympics. any perspectives on that?

jno62 said...

Maybe ALL the leaves will finally come down.

Dude Diligence said...

Port Townsend and Fort Worden look okay for Saturday, just bring a hat and a rain jacket.

Rod said...

Hi Cliff,

West Seattle has sure been getting the 'rain shadow' effect today. Winds out of the south.

The rain sort of stops at the Olympics, and then continues on east of Eden (Bellevue)...