Storm Prediction Center Day 1 Fire Weather Outlook

Created: Wed Sep 2 16:54:02 UTC 2020 ( | )

Click for Day 1 FireWX Areal Outline Product

   ZCZC SPCFWDDY1 ALL
   FNUS21 KWNS 021653

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   1153 AM CDT Wed Sep 02 2020

   Valid 021700Z - 031200Z

   ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR SOUTH-CENTRAL AND
   SOUTHEASTERN MONTANA...
   ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN
   MONTANA...SOUTHWESTERN NORTH DAKOTA...PORTIONS OF CENTRAL AND
   EASTERN WYOMING...

   Only minor modifications have been made to the elevated area on
   account of current surface observations. Areas of 20-35 mph winds 
   with gusts into 25-45 mph range are already being observed in
   Montana this morning. Significant fire weather conditions are still
   expected to develop this afternoon across south-central and
   southeastern Montana.

   See the previous discussion for further forecast details.

   ..Wendt.. 09/02/2020

   .PREV DISCUSSION... /ISSUED 0145 AM CDT Wed Sep 02 2020/

   ...Synopsis...
   A strong shortwave trough will move southward across the northern
   U.S. as a ridge of high pressure begins to build over the West. A
   deepening area of low pressure will drag a dry cold front
   southeastward across the northern Rockies and adjacent plains
   bringing very strong winds and low humidity. Extremely critical fire
   weather conditions appear likely.

   ...Southern Montana...
   Critical and extremely critical fire weather conditions are likely
   to develop this afternoon ahead of the strong dry cold front moving
   across the northern Rockies. Strong gradient winds associated with
   the deepening low and cold front will be bolstered by surface
   momentum transfer from a 70-80 kt mid-level jet along the southern
   end of the shortwave trough. Model soundings show an environment
   extremely favorable for rapid wind-driven fire growth/spread with
   boundary-layer wind gusts in excess of 50 mph likely. Strong daytime
   heating, with temperatures in the 80s and 90s F will keep surface RH
   low near 10%. With adequate fuels, strong downslope flow, and dry
   conditions, extremely critical fire weather conditions appear
   likely. There is a significant risk of extreme wind-driven fire
   behavior and blowups along and ahead of the dry front. Gusty winds
   will likely persist behind the front, but increasing RH recoveries
   to near 40% should limit the potential for extreme fire weather
   conditions after sunset. 

   Into eastern Wyoming and the western Dakotas, critical fire weather
   conditions are likely on the fringes of the stronger flow aloft.
   While winds will be weaker, a lee trough and downward momentum
   transfer should support surface winds of 20-25 mph with surface RH
   below 15%. The favorable meteorological overlap with widespread
   critically dry fuels justifies the inclusion of critical
   probabilities.  

   ...Lee of the Cascades...
   Locally elevated fire weather conditions may develop across the
   Columbia Basin and in the lee of the Cascades. The strong mid-level
   jet overhead will support gusty surface winds of 20-30 mph, though
   humidity values will only be marginally supportive due to cooler
   temperatures behind the departing front. This suggests any fire
   weather conditions will be localized in nature.

   ...Please see www.spc.noaa.gov/fire for graphic product...

      

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