Parade of storms

After a quiet beginning to December, the pattern is about to change as a parade of storms track into the region.   This is good news for our mountain snow pack which is running behind.

This map should look much different in a couple weeks.  Let's take a look at the pattern going into the early next week followed by a more detailed analysis of the first two storms expected.

First system arrives today (Sunday) beginning in the Cascades late this afternoon.  While not much of a storm, we will call it Storm #1 for simplicity sake.  Then follows Storms #2, #3, and #4.  These will carry more precipitation as well as the potential for gusty winds.  The yellow lines on the maps that follow show a strong westerly flow across the Pacific Ocean into our region.  The green shaded areas show high moisture content which you will see over our neck of the woods for each storm.  Take a look. 

00z/Dec 9th GFS model forecast of 500mb heights and 700-500mb relative humidity valid 10 PM PST Sunday

00z/Dec 9th GFS model forecast of 500mb heights and 700-500mb relative humidity valid 4 PM PST Tuesday

00z/Dec 9th GFS model forecast of 500mb heights and 700-500mb relative humidity valid 4 AM PST Friday

00z/Dec 9th GFS model forecast of 500mb heights and 700-500mb relative humidity valid 10 AM PST Dec 16th

Several storms moving through will bring unsettled conditions.  You will notice the flow over our region does turn a bit more southwesterly with the last two storms which may bring slightly milder air.  The mountains will see LOTS of snow.  This mild/wet pattern may persist in the 8-14 day time frame per the latest outlooks from the Climate Prediction Center.

CPC 8-14 Day Temperature Outlook issued December 8th valid Dec 16-22

CPC 8-14 Day Precipitation Outlook issued December 8th valid Dec 16-22

Sunday Night/Monday: Snow Timing and amounts

When will the snow start?  Let's begin with this afternoon (Sunday)

00z/Dec 9th GFS Forecast of Precipitation type valid 4 PM PST Sunday

Snow reaches the Cascades late in the afternoon spreading into Central Washington in the evening.

00z/Dec 9th GFS Forecast of Precipitation type valid 10 PM PST Sunday

Snow then moves into Eastern WA and North Idaho overnight. 

00z/Dec 9th GFS Forecast of Precipitation type valid 4 AM PST Monday

Snow becomes confined to far northeast WA, North Idaho Panhandle, and Cascades, mid to late Monday morning.

00z/Dec 9th GFS Forecast of Precipitation type valid 10 AM PST Monday

This should spell light accumulations for most towns.  Here is a look at our forecast issued Sunday morning.

NWS Forecast snow accumulation issued 3 AM PST Sunday valid through 10 AM PST Monday

Tuesday Storm: 
What about the Tuesday storm?  Looks like it will start off as snow for the palouse and most areas north of Moses Lake.

00z/Dec 9th NAM Forecast of Precipitation type valid 10 AM PST Tuesday

Milder air does surge north Tuesday evening, with snow changing to rain in Spokane.

00z/Dec 9th NAM Forecast of Precipitation type valid 7 PM PST Tuesday

Other models suggest a similar scenario for Tuesday but the forecast will continue to be fine tuned.  This storm has the potential for travel impacts especially over the mountain passes and northern valleys.  For the latest forecast updates, please check our forecast here.