Storm Prediction Center Fire Weather Outlook

• Day 1 fire weather outlook and map
• Day 2 fire weather outlook and map

Day 1 Fire Weather Outlook

	    
   NWS Storm Prediction Center Norman OK
   1115 AM CDT Sat Sep 18 2021

   Valid 181700Z - 191200Z

   ...CRITICAL FIRE WEATHER AREA FOR THE GREAT BASIN AND NORTHERN
   ROCKIES...

   Today's fire weather forecast remains on track, with only minor
   modifications needed based on the latest weather and fuel guidance.
   The primary adjustment with this forecast update was to extend the
   northern Rockies Elevated fire weather area farther east into
   portions of west-central South Dakota, western Nebraska, and north
   eastern Colorado, where minimum RH values less than 10% (near 5%
   locally), sustained surface winds of 15-20 mph, and receptive fuels
   are expected. While some of these areas may see a bit lighter wind
   speeds (e.g., across portions of Northeast Colorado where sustained
   winds of 10-15 mph are more likely) ERC values exceeding the 90th
   percentile across the area coupled with the extremely low minimum RH
   values should foster Elevated fire weather conditions this
   afternoon. 

   Please see the previous discussion below for more information on
   today's fire weather forecast.

   ..Elliott.. 09/18/2021

   .PREV DISCUSSION... /ISSUED 0107 AM CDT Sat Sep 18 2021/

   ...Synopsis...
   Elevated to critical fire weather conditions remain likely today as
   winds increase in response to an approaching upper-level trough in
   the Pacific Northwest. Hot, dry, and windy conditions across much of
   the West yesterday aided in curing fuels, which will help support
   widespread fire weather concerns today. While this system will bring
   beneficial rainfall to parts of the Pacific Northwest, thunderstorm
   chances across Utah, western Colorado, and southwest Wyoming may
   pose a low-end lightning-driven fire weather concern. 

   ...Western Great Basin into Southwest Montana...
   VWP observations over the past few hours from ID and MT show
   strengthening mid-level flow as the upper-level wave continues to
   move onshore across the Pacific Northwest. This trend is expected to
   continue through the day as an axis of stronger flow becomes
   established from northwest NV into ID and western MT ahead of a cold
   front. Diurnal boundary-layer mixing and a nearly uni-directional
   wind profile will allow for efficient downward transfer of stronger
   winds aloft. Ensemble guidance continues to show high probabilities
   for 20-25 mph winds through this corridor with gusts up to 30-40 mph
   (and possibly up to 40-50 mph for wind-prone locations). Receptive
   fuels are already in place for most locations and RH reductions into
   the low teens are expected. Critical conditions remain most likely
   through this northwestern NV-southwest MT corridor, but may extend
   as far south as the lee of the central/southern Sierra. There is
   some uncertainty regarding the westward extent of both critical and
   elevated conditions due to cloud cover/rainfall associated with the
   approaching cold front.

   ...Southern Montana to northeast Wyoming...
   Southwesterly winds will likely increase to 15-25 mph this afternoon
   as a surface low deepens over the Canadian Prairies. Downslope
   affects will aid in RH reductions into the low teens to low 20s, and
   boundary-layer mixing will support wind gusts upwards of 25-35 mph.
   Critical conditions are expected across south-central MT into
   northeast WY where downslope warming/drying will be strongest in the
   lee of the terrain, but may occur as far north as northeast MT. 

   ...Utah, Western Colorado, and southwest Wyoming...
   Thunderstorms are likely today across much of UT and into adjacent
   areas of western CO and southwest WY as a surge of monsoonal
   moisture shifts northward in tandem with a weak upper-level impulse.
   Recent fuel analyses indicate some locations have receptive fuels
   with ERC values above the 75th percentile and fine fuel moisture
   values below 5%. As such, lightning may pose a low-end fire weather
   concern. However, no highlights will be introduced given the overall
   modest fuel status of the region and high wetting rain potential.

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

      

Day 2 Fire Weather Outlook

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