Snow then Bitterly Cold

By now, many have probably heard of the much colder temperatures arriving for next week.   These may be some of the coldest temperatures the region has experienced in at least the past 10 years.  If you haven't already, now is the time to prepare!

Before we get into the details of the bitter cold, let's briefly talk about the weather pattern going into Christmas weekend which is expected to bring snow to much of the region.

A very cold weather system will stall over the region from Friday through Monday, as shown by the dark blue colors from this model simulation showing anomalous low pressure over the region.

18z Dec 23rd GEFS forecast of 500mb heights and anomaly (shaded) valid Dec 24-27th, 2021

The cold system will result in a very unstable atmosphere, with bands of moderate to heavy snow showers each day.  Pinpointing where these set up is often difficult to predict, but can produce localized areas of heavy snow accumulations.  Right now models are showing the heaviest snow amounts over far NE Washington into the Idaho Panhandle.

But the big story continues to be the bitterly cold for next week.  

The same model as above shows the really cold stuff settling in on Monday with the coldest days likely Tuesday and Wednesday (as noted by the bright purple shading), with gradual "warming" later in the week but still temperatures well below normal.

18z Dec 23rd GEFS forecast of 2 meter temperature anomaly (shaded) valid Dec 27, 2021 - Jan 1, 2022

So how cold are we talking?  Well if your thrown in all of the computer models together (about 100 of them), and take the median forecast, this is what it shows for the forecast low temperature on Wednesday, Dec 29th.

National Blend of Models (NBM) forecast of low temperature Dec 29th, 2021

Wow!  Some locations colder than -10F!  It is worth noting low temperatures can be tricky to forecast when it comes to extreme cold as temperature drops are very dependent on winds becoming light and clearing of the skies.  But this is the median of many model forecasts, so it's possible it could be even colder, or warmer than the numbers shown above.

You may ask when was the last time Spokane dropped all the way down to -10F or colder.  Well it's been awhile, but certainly can happen.  

It hasn't happened since the 2010-11 winter, where there were 3 instances of the bitterly cold nights.

And what about high temperature? 

National Blend of Models (NBM) forecast of high temperature Dec 29th, 2021

Many areas possibly not getting out of the single digits according to this model blend forecast!

With areas of moderate to heavy snow through Christmas weekend, and bitterly cold temperatures next week, be sure to keep up to date with the latest forecasts, advisories, and warnings at www.weather.gov/spokane