Snow in the Forecast

It's been nearly 3 weeks since we've had any precipitation.  It is not unheard of to have long dry spells in the winter, but this one has been longer than the average.  But that streak will come to an end on Friday as snow returns to the area.

Currently we still have strong high pressure to our west which has kept us dry, clear and cold.  But there are 3 areas of low pressure that will affect our weather over the next few days in a rather interesting way.  The first low is currently over Alaska, the second is north of Hawaii, and the third is out by the dateline.

Low #1 is going to drop down to the British Columbia coast while Low #2 heads to the Pacific Northwest.  Low #2 will reach our area early Friday morning.

Since Low #2 is coming at us from just north of Hawaii, it will a little on the warm and moist side.  Initially our precipitation will start off as snow Friday morning, before sunrise.  But as the day progresses, some of that snow will change to rain over southern Washington.  How far north the rain will spread is a tough call.  The GFS model has been consistent in its forecast, keeping our precipitation all snow.  But it's been doing that all winter.  The more reliable ECMWF had been consistent in its forecast, changing to the snow to rain after about an inch of snow had fallen.  But the most recent ECMWF forecasts have trended more towards keeping the snow going a little longer.

Here's the latest ECMWF snowfall forecast, compliments of PivotalWeather.  Less than an inch for Spokane and points south, with 1-3" for areas to the north.

Below is the snowfall forecast from the GFS.  It has 3" of snow for Spokane, and 4-7" for areas to the north.  But as I said, the GFS has been giving us too much snow all winter.

One reason that the snow will want to change to rain in the increasing wind from the south.  A surface low pressure system will pass by our area, creating breezy conditions throughout Friday and into Saturday, with wind gusts up to 25 mph (or 35 mph in Spokane).  This will bring our high temperature on Thursday, Friday and Saturday to around 40F.  And there's a good chance we may remain above freezing Friday night.

So the most likely scenario is snow for Friday morning, ending by late morning as a southwest wind develops.  Then rain or wet snow redevelops Friday afternoon as the wind continues.  Temperatures will likely remain above freezing Friday night, so expect most of the snow to melt by Saturday morning.  

For the rest of the weekend, the atmosphere will be rather unstable.  So expect snow showers both days.

After this, Low #1 will become stationary near Vancouver Island, while Low #3 approaches the West Coast early next week.  There's still a lot of uncertainty about this scenario, but we could see more snow from this situation Monday or Tuesday, but most likely the main precipitation will stay to our south.

It does appear that colder Canadian air will filter into our area Monday and Tuesday.  This doesn't look like some "arctic blast".  We'll have northeast winds on Monday and Tuesday up to 15 mph.  Temperatures will drop into the teens and possibly single digits at night with 20s during the day under mostly cloudy skies.