White Christmas?

As of the time of this writing (2 PM Thursday), the Spokane Airport was a mild 45F with rain falling, when the normal high is only 31F.  These mild temperatures sure are interfering with those dreaming of a White Christmas!  Well there is still hope that we will detail in this blog.

Let's begin with historical odds.  This map shows historical chances of having 1" of snow or more on the ground on Christmas Day.

 An interactive version of this map is available at this link.  It shows historical odds are 57% Spokane, 47% downtown Wenatchee, and 16% Lewiston.

So what about this year?  Let's begin with the snow that is out there now with this morning's 10 am snow analysis.

NOHRSC Snow analysis 10 AM PST (18z) December 20th, 2018

Wow!  Not only a lack of snow around our neck of the woods, but most of the US is free of snow cover.  Here is a more zoomed in map of our region.

NOHRSC Snow analysis 10 AM PST (18z) December 20th, 2018

So most locations outside of the mountains, Cascade valleys, and some valleys near the Canadian border need some snow, and soon!  What does the future hold?

Well a storm is forecast to track through the region Saturday night and Sunday as the GFS model shows.

12z Dec 20th GFS forecast of 500mb heights and 700-500mb Relative Humidity valid 4 AM (12z) PST Sun Dec 23, 2018

Looks like temperatures will start off cold enough Saturday night into Sunday morning for snow with the possible exception being the Lower Columbia Basin and around La Crosse and Lewiston-Clarkston Valley.  The I-90 corridor from Moses Lake to Ritzville will be near the rain/snow line. Here is the GFS forecast of precipitation type Sunday morning.

12z/20th GFS forecast of precipitation type/intensity valid 4 AM PST (12z) Sunday, December 23rd, 2018

So the potential exists for light to moderate snow accumulations for most locations Sunday morning.  But will it stick around through Christmas Day? And any more storms after Sunday?  Let's talk temperatures first.  Whether this snow sticks around will depend on how much falls as temperatures for most valleys will warm into the mid to upper 30s Sunday and Christmas Eve resulting in some melting.  Here are the forecast high temperatures for Sunday and Christmas Eve.

Not all that warm, but should see a little melting of snow for most lower elevations.  

So what about the weather on Christmas Eve into Christmas Day?   Another storm approaches but the current model projection from the GFS late on Christmas Eve take the precipitation mostly to our south across Oregon, southern Idaho, and California.

12z/20th GFS forecast of precipitation type/intensity valid 10 PM PST Monday, December 24th, 2018

This particular solution would give the Washington Cascades some snow as well, but other solutions take the storm further south like the Canadian model below.  This morning's European model is similar to the Canadian model.

12z/20th Canadian model forecast of precipitation type/intensity valid 10 PM PST Monday, December 24th, 2018

And here is the GFS model projection for Christmas morning.

12z/20th GFS forecast of precipitation type/intensity valid 10 AM PST Tuesday, December 25th, 2018

Models are trending further south with this storm, but this is still several days out and the track could still change so be sure to monitor latest forecasts.

To summarize, while there is a lack of snow out there now, light to moderate snow accumulations are forecast for most locations Sunday morning.  But expect some melting of this snow prior to Christmas Day.  We will continue to monitor the track of the storm that follows which is currently more likely to impact Oregon, California, and southern Idaho.

As always, forecasts are refined as we get closer so be sure to check our web site for the latest forecasts at this link