The same atmospheric set-up helping to bring significantly colder air and snow to a region that saw a 100 degree heatwave days ago is also helping fan fires along much of the western United States. In today’s Fire Weather Outlook from the National Weather Service’s Storm Prediction Center (SPC), large areas of California, Nevada, Oregon, Idaho, and Arizona are under an elevated or critical fire weather risk. An elevated risk of fire weather conditions also exists over southern Washington and northwestern Utah.
The SPC says that the strong offshore pressure gradient resulting from central Rockies high pressure and West Coast low pressure will remain in place much of the day, although a weakening trend will start later this evening as the high weakens and shifts eastward toward the central Plains. Meanwhile, subsidence aloft on the west side of a cutoff low over the Four Corners area will continue to maintain a very hot, dry airmass across much of the western states. The overall pattern will maintain widespread elevated fire weather conditions along with a few areas of critical fire weather near terrain-favored areas.
With humidities in the 7-15% range and winds in the 20-30 mph range with gusts to 45 mph, any flame could quickly spread in areas experiencing the fire weather conditions.