A Snowy Period Ahead for the Pacific Northwest

 We are currently at the end of the normal lowland snow period in the Pacific Northwest, with the sun rapidly strengthening.   

But not this year.  

The latest forecasts have significant lowland snow over western Washington during the next few days, with many of you experiencing several inches of the white stuff.

And we have an extended, colder-than-normal period ahead.  

Let me give you the details of the forecast.

Today, we have a cold air mass over the region...cold enough to snow anywhere in Washington State.  Temperatures dropped into the teens and twenties in western Washington and single digits in eastern Washington (see low temperatures below).  Several daily low-temperate records fell last night.

This evening a moist occluded front will approach, spreading precipitation over the region.   Snow will move into the Puget Sound region after 8 PM.

Note that the story in the Seattle Times is very wrong, suggesting snow will come in this afternoon around 4 PM.  It also talks about an influx of Fraser River cold air later today.  Simply not correct.

Let me show you the cumulative snowfall totals over Seattle from the most powerful forecast tool available:  an ensemble of many high-resolution weather predictions, each slightly different. (Time is in UTC, 06Z/26 is 10 PM tonight).  A rapid start of the snow around 9 PM.  The black line is the ensemble average....generally a very good forecast.  Just under 1.5 inches.  And it is all over by around 3 AM.

The distribution of snow will be quite varied, so let me show you the accumulated snowfall through 10 AM Sunday (below).

Little snow near the Strait of Juan de Fuca and right on the Pacific Coast.   A Puget Sound convergence zone feature will increase snow east of the Olympics.  Lots of snow in the mountains and a good snow area in eastern Washington east of the Columbia River.  More snow east of Seattle than in the city.

Temperatures will be on the edge for snow.  It will be wet snow and there will be less snow near the water. Note that snow depth will be less than snowfall.  Snow melts and compacts at the surface.

Temperatures will warm into the lower 40s on Sunday (again stronger sun, plus onshore flow after the front).  Thus, I expect the roads to rapidly melt out.

But we are not done with snow.  

On Monday, a low-pressure center will approach the southwest Washington coast, drawing cold air back into the lowlands from the interior.   This low (and associated upper-level trough) will bring more snow into the region, first in western Oregon and then in western Washington.

The 24-h snowfall ending 4PM Monday shows substantial snow over the coastal areas and southwest Washington.  Portland gets several inches.

And then in the next 24-h (ending 4 PM Tuesday),  Puget Sound and Seattle get several more inches.

And folks, this is not the end of the snow threat. 😀

The latest 8-14 day temperature outlook from the NOAA/NWS Climate Prediction Center is enough to make you want to lay in a supply of thermal underwear and hot chocolate.

And if you think what is happening here is unusual, the cold, snow, rain, and winds in California are extraordinary and record-breaking for this time of the year.