Increasing Chances for Light Snow During the Next Week

When you have gasoline and matches laying about, there is always the chance the two might join forces to produce a fire.

During the next week, two critical ingredients for lowland snow will be in our neighborhood:  cold air and occasional weather disturbances coming from a variety of directions.  Will they combine to provide some low-level snow? 

THAT is the question.  And I believe the probability of at least some light snow is becoming more probable, particularly away from the water.

But we are running out of time for a significant lowland snow event.  As shown below for Sea Tac Airport, extreme daily snowfall (blue lines) really declines after the first week of March.  Average temperatures are slowly warming now and the sun is rapidly gaining strength.

The latest European Center ensemble forecast (51 separate forecasts!) for accumulated Sea Tac Airport snowfall, is suggesting a real chance of modest snow during the next several days, with very light snow sometime after 4 PM Friday (23/00), with accumulations to up to a few inches by Monday evening.

The US GEFS ensembles (only 21 members) for accumulated snowfall at SeaTac is also going for light snow, but with lots of uncertainty in the forecasts, with the average of around 1 inch by Sunday morning and around 2 inches early next week.

What about accumulated snowfall in the latest high-resolution UW WRF model?  Between now and 4 PM Saturday, not very much near sea level, with perhaps a bit of wet snow mixing in with the rain tomorrow.  But plenty of snow in the mountains.

 By the next  24 hr (ending 4 PM Sunday) brings an inch or two to the lowlands, with less right near the water.  The reason?  Because the temperatures will be marginal for snow.

The European Center higher resolution model snow forecast through 10 AM Sunday shows a few inches of snow over portions of the western WA lowlands, and as with the UW model, it is more spotty near the water.

The longer-term accumulated snow through 10 AM Wednesday indicates serious snow, with huge snow dumps over the Oregon Cascades and east of the Cascade crest.

We will be back in the freezer early next week, with much cooler air over us.  Below is the forecast for 10 AM Tuesday--blues and purples are cold air.  A very strong pressure difference will be found over the Cascades, with very strong easterly winds in the Columbia Gorge.  However, we will lack precipitation at that time due to strong easterly flow crossing the Cascades--thus, not much chance of snow then.

So the bottom line of all this is that tomorrow an approaching weather system will bring rain to the lowlands and snow to the mountains.

On Saturday, expect showers, with considerable snow showers across the region.  Some accumulation is possible away from the water.  Snow showers will continue into Sunday morning, followed by drying Sunday afternoon.



from Cliff Mass Weather and Climate Blog https://ift.tt/2twv4fQ