The Week Ahead – Snowflakes Before Christmas?

Many out here remember the epic December snow and White Christmas of 2008, but do you remember 2017? 

For the week ahead:

After another rainy Saturday that became blustery last night, we’re trying to dry out this morning, in between weather systems, for much of Sunday before steadier rain returns late tonight.  The mountains will be battling between rain and snow, but snowpack melt looks minor and little potential threat for river flooding at this point.

As previously mentioned, another front looks set to move in later tonight into Monday, bringing another good dose of rain, heavy at times Monday morning that should gradually decrease in the afternoon and evening.  Models are mixed currently as to whether or not we’ll see another round of southerly winds develop Monday afternoon.

Now is where things get more interesting..

An upper trough and cold front will bring down colder air out of the Gulf of Alaska and B.C. later Monday.  At this point, both the Euro and NAM main model runs are showing rain potentially changing to wet snow for a few hours in the afternoon and/or evening for the lowlands Monday into Tuesday, but bear in mind this is very much a fringe event (snow level ~500-1,500 ft), and we’ll be battling a drying out of the atmosphere as the temperatures aloft decline. 

Nevertheless, there is the possibility of a little lowland snow in the foothills. No forecasted accumulations (yet). Something to keep an eye on for sure. As we know from observational experience, this could very easily be just a cold rain event. Most snow forecasts are particularly tricky in Western Washington.  Not just for the cold and the precipitation mixing, but also the dramatic differences depending on location, whether that be mixing lines, convergence zone, elevation differences, or just being the lucky recipient of a rogue shower temporarily bring the snow level down with heavy precipitation. 

We should then dry out on Tuesday through Thursday as an upper ridge builds over the area. Lacking cloud cover, it could be very chilly (below freezing) Wednesday and Thursday mornings.  Earlier runs had hope for at least a nice frosty Christmas morning, but now it looks as if an incoming system will provide enough cloud cover to keep things generally overcast Christmas morning at best. Of course, that all assumes as the week progresses, the inherent uncertainty with longer-term forecasting continues to point to rain, holding off on the rain until later on Christmas day.  GFS model is already trying to rush the rain in time for AM hours.  Boo:( 

So for now, we’ll go with rain likely to return Christmas Day and Saturday. Highs should be near normal.

Since 1980 at Snoqualmie Falls on Christmas Day, the average High is 45°, and the average Low is 34°

Have a great week!

[Originally published at Snoqualmie Weather blog During active weather follow more frequent updates @snoqualmiewx or on Facebook]