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
   0127 AM CDT Thu Aug 13 2020

   Valid 131200Z - 141200Z

   ...CRITICAL FIRE WEATHER AREA FOR EASTERN IDAHO AND EXTREME
   NORTHEAST UTAH INTO CENTRAL AND SOUTHERN WYOMING...

   ...Synopsis...
   A well-defined mid-level shortwave trough will traverse the Northern
   Rockies through the period, with relatively strong 500 mb flow aloft
   overspreading a deep, well-mixed boundary layer during the afternoon
   hours. Downward momentum transport, downslope flow, and channeled
   flow in terrain favoring areas will support dry and windy conditions
   conducive to wildfire spread. Deep-layer ascent associated with the
   trough may also support the development of isolated thunderstorms
   atop the aforementioned dry boundary layer, with a couple dry
   strikes possible. Farther south into the eastern Great Basin and
   Four Corners regions, the dry and windy conditions are expected to
   be more brief and localized given the southward displacement from
   upper support. 

   ...Northern Rockies into the northern Great Basin/Southern Parts of
   the Pacific Northwest...
   15-25 mph sustained westerly flow overlapping 10-20% RH is expected
   to become common, from the Harney Basin in southeast Oregon to the
   lee of the Rockies in eastern Wyoming by afternoon, hence the
   Elevated area. While spread among guidance is quite large, there is
   a possibility that locally Elevated conditions may occur along the
   lee of much of the Cascades as well. The strongest westerly
   sustained winds (20-25 mph with higher gusts) are expected across
   the Snake River Plain in southern Idaho to the Great Divide Basin in
   southern Wyoming, where a Critical delineation has been maintained. 

   Farther north, across southwest Montana into Yellowstone Country,
   high-based isolated thunderstorm development remains a possibility.
   The latest model guidance however, struggles to depict meaningful
   instability, suggesting that lightning should be sparse overall. In
   addition, modest precipitation accumulations have occurred within
   the past week, and fuels remain modestly receptive to fire spread.
   As such, an isolated dry thunderstorm area was not introduced,
   though a couple dry strikes and subsequent fire ignitions cannot be
   completely ruled out. 

   ...Central Rockies into the eastern Great Basin and Four Corners...
   At least locally Elevated surface winds/RH are possible across parts
   of the Great Basin into the Four Corners by afternoon peak heating,
   with the greatest likelihood for such conditions potentially
   occurring across eastern Nevada into western Utah. At the moment,
   the greatest limited factor for an Elevated introduction (or
   southward expansion of the ongoing Elevated) is the lack of stronger
   flow aloft to be transported downward in a dry boundary layer to
   support a stronger, more widespread wind field.

   ...Parts of northwest Texas into southwest Oklahoma...
   By afternoon peak heating, up to 15 mph sustained southwesterly
   winds may accompany a weak dryline for at least brief periods, with
   RH dropping to 15-20%. While fuel receptiveness to wildfire spread
   is not overly high, fuels are dry enough to support some wildfire
   growth potential in the presence of the aforementioned overlapping
   surface conditions. However, the brief, localized nature of the
   overlapping surface conditions and fuels precludes an Elevated area
   at this time.

   ..Squitieri.. 08/13/2020

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

      

Day 2 Fire Weather Outlook

 Storm Prediction Center Norman OK
   0138 AM CDT Thu Aug 13 2020

   Valid 141200Z - 151200Z

   ...Synopsis...
   The mid-level shortwave trough, responsible for promoting favorable
   wildfire-spread conditions across the western CONUS on Day 1, is
   expected to eject into the northern CONUS on Day 2/Friday.
   Nonetheless, some residual modest mid-level flow pivoting around the
   backside of the trough is expected to overlap a dry, deep boundary
   layer across portions of the northwestern CONUS. As such, dry and
   occasionally breezy conditions are expected to support some
   wildfire-growth potential during the afternoon hours across parts of
   the northern Rockies.

   Meanwhile, the northern periphery of a northward moving mid-level
   moisture plume is expected to overspread a heated, deeply mixed
   boundary layer, with isolated thunderstorm development and perhaps a
   few dry strikes possible.

   ...Portions of the Northern Rockies...
   During the afternoon, the stronger northwesterly mid-level flow is
   expected to be transported downward via boundary-layer mixing to
   promote 15-20 mph sustained northwesterly flow, coinciding with
   15-20% RH. Locally Critical conditions may also occur across terrain
   favoring areas, including the Snake River Plain and Great Divide
   Basin. Farther north, widespread 15 mph sustained northwesterly
   surface winds are also expected across much of northern and eastern
   Montana by mid to late afternoon. However, model guidance varies in
   terms of how low RH will get, with some members depicting RH between
   15-25% and other members struggling to show widespread RH below 25%.
   Given uncertainties related to RH, along with fuels remaining modest
   to wildfire spread, an Elevated area has been withheld this outlook.

   ...Lee of the Sierra...
   By afternoon, isolated high-based thunderstorms are expected to
   initiate along and to the lee of the Sierra across far eastern
   California into far western Nevada. While precipitable water values
   may be on the high end (0.75-1.0 inch range) with slow storm speeds
   noted, some of the latest guidance depicts classic inverted-V
   soundings, with a dry sub-cloud layer extending past 700 mb. As
   such, at least a few dry strikes are possible, and given receptive
   fuels in place, an isolated dry thunderstorm area has been
   introduced.

   ..Squitieri.. 08/13/2020

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

      

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