NWS Storm Prediction Center - Day 1-2 Fire Weather Outlook
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Dec 16, 2017 Day 1 Fire Weather Outlook
Day 1 Fire
 Population  Cities  CWAs  Interstates  Counties  FEMA Regions  Day 1 Surface Analysis 

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 28,126 17,278,259 San Jose, CA...San Francisco, CA...Oakland, CA...Riverside, CA...Stockton, CA...
   FNUS21 KWNS 161608

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   1008 AM CST Sat Dec 16 2017

   Valid 161700Z - 171200Z


   The ongoing forecast is on track with no changes needed.  Several
   areas of gusty northerly/northeasterly flow will persist across
   portions of California today amidst very low RH values, resulting in
   potential for rapid fire spread.  Farther east in the Plains,
   elevated fire weather conditions will develop for a few hours in the
   afternoon with RH values falling to around 15-20% within the
   elevated area.  Locally elevated fire weather conditions can also be
   expected in northeastern Oklahoma and vicinity, where 10-20 mph
   southerly winds will briefly combine with minimum RH values of
   around 25-30%.

   See the previous forecast below for more detail.

   ..Cook.. 12/16/2017

   .PREV DISCUSSION... /ISSUED 0156 AM CST Sat Dec 16 2017/

   Strong northerly deep-layer flow on the back side of an amplifying
   upper trough over the Great Basin will overspread much of CA today.
   At the same time, surface high pressure will build over the Pacific
   Northwest today, and into the Great Basin tonight. This will result
   in an increasing surface pressure gradient first over northern CA.
   As stronger high pressure slides southward into the Great Basin this
   evening, offshore gradients will increase over southern CA. The net
   result will be a large area of elevated to critical fire weather
   conditions across much of California today and tonight.

   Increasing southerly deep-layer flow will overspread the southern
   Plains today as a shortwave trough lifts northeast from northern
   Mexico into TX by this evening. At the surface, a lee low will
   develop over the central/southern High Plains and an increasing
   pressure gradient across the region will aid in development of gusty
   surface winds and elevated fire weather conditions will be possible.

   ...Portions of Central into Northern CA Today and Tonight...

   Gusty north winds were already occurring as of 07z across portions
   of the Bay Area mountains and foothills. RH values are expected to
   fall critically low later this morning and elevated to critical
   conditions are expected to persist through the remainder of the
   period across portions of central into northern CA. Critical
   conditions are most likely in the mountains and foothills near the
   Bay Area southward along the Diablo and Santa Cruz Mountain Ranges
   into adjacent portions of the Sacramento Valley. RH values will fall
   into the 10-20 percent range during the day with north winds around
   15-30 mph with higher gusts possible. 

   ...Portions of Southern CA...

   Gusty winds were already occurring as of 07z across parts of the
   Santa Barbara County mountains in conjunction with very low RH.
   Critical conditions will continue through this evening as north to
   northeast winds of 15-25 mph with stronger gusts persist. Further
   south and east toward Ventura, Los Angeles, Orange and western San
   Bernardino and Riverside Counties, gusty northeasterly winds will
   return Saturday night into Sunday morning. Expect sustained winds of
   20-30 mph with higher gusts. RH values will fall into the 15-25
   percent range Saturday night, before falling further during the day
   on Sunday.

   ...Portions of the Central and Southern High Plains...

   Breezy and dry conditions are expected across portions of the
   central and southern High Plains today. As temperatures warm into
   the 50s to low 60s, boundary-layer mixing to around 2-3kft will
   ensue, resulting in further drying and downward transport of
   stronger midlevel winds. RH values of 20-30 percent will be
   widespread with sustained winds around 15-20 mph and higher gusts.

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


   Source:  NWS Fire Weather Outlook
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