Lowland Snow over Western Washington Tonight? American versus European Models

 A very interesting forecast dilemma is before local meteorologists tonight.

On one hand, the U.S. high-resolution model (HRRR) is predicting as much as 8 inches over the South Sound and 5 inches at SeaTac Airport by 11 AM Friday morning. The U.S. GFS model is doing the same.  Most of the snow will fall overnight.

 

In contrast, the European Center model, which is generally the most accurate (remember the missing bomb cyclone in December?), is NOT going for lowland snow.  Zippo.

Keep in mind, this is snowfall, not snow depth.   This is going to be very wet, melting snow in any case, and snow depths will be MUCH, MUCH less.

An interesting aspect of this event is the large north-south temperature change forecast over the region.  Below is the forecast temperatures around 5000 ft  (850 hPa pressure) at 5 AM tomorrow morning.   Huge contrast over southern Washington (blue cold, green warmer).  A small error in position would be significant.

Currently, the freezing level is around 1600 ft at SeaTac (see below), much too high for snow reaching sea level.   The snow level (where all the snow has melted) is about 1000 ft below the freezing level.  But it should decline slowly.

What about uncertainty in the forecasts?  It is HUGE.   The UW high-resolution model, forced by many global models, shows a wide range of possibilities. Many forecasts are for zero, others as much as 4 inches of snowfall (NOT SNOW DEPTH).

I suspect the European Center projections will be closer to the truth.  Near sea level, some of you may see some flakes tomorrow morning in the central and south Sound near sea level (500 ft and below elevation).  But nothing significant.  Snowfall will increase rapidly above 500 ft.

In contrast, the central and south Cascades will be hit hard (see accumulated snow through Sunday morning).  Feet of fresh snow.  The mountains of SE Washington will also get plentiful powder.