Storm Prediction Center Day 1 Fire Weather Outlook

Created: Wed Dec 6 07:20:02 UTC 2017 ( | )

Click for Day 1 FireWX Areal Outline Product

   ZCZC SPCFWDDY1 ALL
   FNUS21 KWNS 060718

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   0118 AM CST Wed Dec 06 2017

   Valid 061200Z - 071200Z

   ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF VENTURA AND
   LOS ANGELES COUNTIES FOR LATE TONIGHT IN SOUTHERN CALIFORNIA...
   ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

   ...Synopsis...
   Critical fire weather conditions will continue today and tonight
   across parts of southern CA as moderate to strong Santa Ana winds
   occur. Extremely critical conditions now appear likely across parts
   of Ventura and Los Angeles counties late tonight into early Thursday
   morning. These dangerous high-end critical to extremely critical
   conditions will continue into Day 2/Thursday.

   A highly amplified upper pattern will remain across the CONUS today
   as a large-scale upper trough/low encompasses the central/eastern
   CONUS. An upper ridge will be centered over the eastern Pacific and
   western CONUS. At the surface, a strong and broad area of high
   pressure will remain across the northern Rockies and Great Basin
   through the period. Generally cool post-frontal conditions will
   temper fire weather concerns east of the Rockies.

   ...Portions of Southern CA...
   The LAX-TPH surface pressure difference has averaged around -11.8 mb
   over the past few hours. Corresponding strong/gusty northeasterly to
   easterly winds of generally 20-30 mph continue per recent surface
   observations across much of the higher terrain of coastal southern
   CA. Higher gusts of 40-50 mph have been observed as well.

   A prolonged offshore wind event will continue across parts of
   southern CA today as the surface pressure gradient remains strong
   enough to support 20-30 mph northeasterly/easterly sustained winds.
   Gusts of 40-50 mph will likely continue across the
   mountains/foothills of coastal southern CA. RH values will remain
   critically lowered in the 5-15% range owing to both low-level
   downslope warming/drying and diurnal heating, with very poor to
   nonexistent overnight recovery. Latest deterministic and ensemble
   guidance indicates that the surface pressure gradient will be
   somewhat weaker through at least the first half of the Day
   1/Wednesday period compared to yesterday. Still, high-end critical
   conditions will remain likely in favored higher terrain, and with
   very dry fuels in place, large fire spread will occur with any
   new/ongoing fires.

   Confidence has increased that the surface pressure gradient will
   restrengthen late tonight into early Thursday morning, and a
   corresponding increase in wind speeds/gusts will occur in this time
   frame. Both the 3 km NAM and experimental HRRR indicate sustained
   winds of 30-35 mph and sub-10% RH values will occur across portions
   of Ventura and Los Angeles counties for the last few hours of the
   Day 1/Wednesday period. Therefore, a small extremely critical area
   has been introduced to account for this threat. Extremely critical
   conditions are expected to become more widespread across coastal
   southern CA on Day 2/Thursday. See the Day 2 Fire Weather Outlook
   for more information.

   ..Gleason.. 12/06/2017

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

      

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