Snow Showers and a Cloudy Arctic

There will be interesting and somewhat unpredictable weather in the next few days.  First lets take a look at the overall weather pattern.  A deep cold low pressure system has taken up residence over BC and will remain in our area for the next few days. This is Low #1 from our previous blog.  Low #3 (north of Hawaii) will come into play in the middle of next week.  More on this in a bit.

This weather pattern is going to do two things.  First, the cold low will keep the atmosphere very unstable.  This will cause snow showers to form.  These will mainly occur in the afternoon and evening hours, but could develop at any time of the day or night.  Most will be random.  But in this situation, there are often very small disturbances in the atmosphere that are difficult to detect and predict, but can organize some showers into a few hours of heavy snow.  

Here's an example of what I'm talking about.  The ECMWF model wants to give about 2" of snow to an area around Davenport tonight (Saturday night), west of Spokane.  Could it happen?  Sure, but it might not be on Davenport.  It could wind up in Spokane, or Cheney, or Newport.  No way to really know.

Most of the computer models are forecasting these random snow showers, all in different locations.  The one thing they do seem to agree on is that the best chance of these showers will be on Sunday night.

The next best chance of widespread snow will probably be on Tuesday night or Wednesday.  Low #3 that I mentioned earlier will track from Oregon into southwest Montana.  But there may be enough moisture on the north side of this low to spread some snow into southeast Washington and the southern Idaho panhandle.  How far north it spreads is the most uncertain part of the forecast.

The Canadian model keeps the snow well south of our area.

The GFS model is farther north, with light amounts of snow reaching northeast Washington while the bulk of the heavy snow remains to our south.

The ECMWF is somewhere in between the two other forecasts, and is probably the closest to what will occur.  (It's worth noting that the ECMWF from last night's forecast had the snow farther north than even the GFS, so there's a lot of uncertainty on this mid-week event).

Even after this potential event, there continue to be chances of snow through next weekend.  Here's the chances of snow at Deer Park for the next 10 days.  Even western Washington and Oregon can expect some snow now and then next week, even on the coast.

The other interesting and unpredictable aspect of the weather will be the temperatures, more specifically, the low temperatures.  Most intrusions of arctic air bring with them clear skies and very dry air.  This allows temperatures at night to really get cold.  We will see cold arctic air push into our are, especially Monday night and Tuesday, with gusts to 25 mph.  But the problem is that the large area of low pressure to our west will be causing a lot of clouds and showers, instead of the crystal clear cold snaps we usually have.  We call this a "cloudy arctic" or "dirty arctic".

This will all play havoc on the nighttime low temperatures.  One valley could have cloudy skies all night, maybe even a snow shower, and remain in the teens or even 20s.  Another nearby location could have clear skies and light winds, allowing the temperatures to drop below zero.  There's just no good way know what exactly will happen.

The weather map below gives an example of this.  It's from the ECMWF and shows what it thinks are the warmest and coldest possible low temperatures on Wednesday morning.  Spokane could be anywhere between 2F and 20F.  Up in BC, the town of Trail could be as cold as -12F, or as warm as 19F.

The coldest temperatures will probably be in the middle of next week, but as we've just discussed, there's no guarantee of that.  

The Climate Prediction Center always updates their outlook for the next month on the last day of the current month.  The update that came out yesterday was similar to their previous outlook for February.  Delayed spring.