November 10, 2017

Big Snow Coming to the Cascades

This should have been posted on Wednesday....

The jet stream is now directed south of Washington State, with the heaviest precipitation going south of us into northern California and southern Oregon (see upper level map at 10 AM today).  Winds are parallel to the height lines, with speed proportion to the gradient (or rate of change with distance) of the height lines.

The 72hr total precipitation for the period ending 4 AM Saturday is impressive, with some areas of northern CA getting 5-10 inches (see below).   Reservoirs in northern CA will begin refilling now, with some like Shasta starting well above normal (Shasta is at 117%).

The jet will remain south of us for a few days.

 But by Saturday, with a deep trough developing offshore, the jet stream and associated flow with be heading right into our region.

 And will continue into our area into next week (see Tuesday night at 10 PM).

As a result, precipitation will substantially increase.   The 72hr total ending 4 AM Wednesday is particularly impressive, with 5-10 inches of precipitable water over the higher terrain of the Olympics and Cascades.

 With sufficiently cool air over us, this means lots of snow, with 2-3 feet being widespread above roughly 4000 ft.  Translation: with the base with have currently, many of the Cascade ski areas will have sufficient snow to open by the middle of next week.


  1. Once the rain gets going is there any historical data to suggest when dry days return?


    I managed to get a great run in at Padilla Bay Shoreline Trail. It's a 4 mile trial this Friday Nov 10 afternoon. My sense it might be mid April 2018 before its dry enough to run again. When it's raining I only run 2 miles near home.

  2. It looks like the forecast changed on Thursday night, shifting to somewhat warmer temperatures and a higher snow level (5000-5500 ft, and lower on Blewett and to the east) through the weekend. Crystal Mt pushed its opening forward, hoping for next midweek if they get more snow out of Monday-Tuesday (and of course Crystal has a lot of snow guns now).


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