Tuesday, December 8, 2015

Another Wind Storm? Not a repeat of 17 November.

Yes, there is another wind storm heading for the Inland Northwest.  But it will NOT be as strong as the 17 November wind storm.  While this event is similar to the storm last month, there are differences.  Let's see in what way.  First, take a look at our blog that we put out before that wind storm.  It's at:


You'll see that we talked about 2 main weather patterns for strong winds.  The November 17 storm was a pattern #2.  Tomorrow's storm will be more of a hybrid between pattern #1 and #2, which is much more common.  In other words, tomorrow's wind storm will be more like what we are used to getting.

For the November wind storm, the surface low that passed by over southern BC was 985mb when it was to our north, and then 977mb in the lee of the Rockies over Alberta.  Below are the surface pressure forecasts for tomorrow's storm.

GFS forecast of Sea Level Pressure for 830am 9 Dec 2015

GFS forecast of Sea Level Pressure for 200 pm 9 Dec 2015
This time around, the low will be about 991 mb over southern BC, and 985 mb in Alberta.  That's about 6-8mb weaker than the 17 November storm.  Also note that the track is slightly south of the storm last month.  This would suggest that the stronger winds will also be shifted farther south than last month.  That's good news for the northern counties (i.e. Bonner, Boundary, Pend Oreille, Stevens), but may be bad news for the southern counties like Whitman, Latah, Nez Perce, Asotin, Garfield, and Lewis.

Also, the jet stream is displaced farther south, over Oregon instead of Washington.  All of this points to a weaker system than November, but still a respectable event that could cause some damage.

Here's the forecast of peak winds:

Comparing this forecast to the previous month, you'll notice that wind speeds are overall weaker by about 10 mph.  The exception to this is in the southeast (Pullman, Lewiston, Winchester), where the forecast is about 10 mph stronger.  So the focus for potential damage will be in those areas.

There is one fly-in-the-ointment to all of this, that wasn't a factor in November.  There is the potential for thunderstorms on Wednesday.  (Yes, this is mid-December.)  We have a VERY moist air mass in place, and the cold front on Wednesday is strong.  This combination could lead to a few thunderstorms.  They won't be "severe".  But, a thunderstorm can bring down stronger winds from the upper levels of the atmosphere.  So any thunderstorms that do form will have to be watched closely.

After the wind on Wednesday, the weather pattern will change to cooler with a better chance for snow in the lower elevations. 


  1. Unfortunately, there are a lot of trees with damage from the last one, even though they didn't go down. They just might this time.