Storm Prediction Center Day 2 Fire Weather Outlook

Created: Fri Dec 15 19:59:03 UTC 2017 (20171215 2000Z Day 2 FireWX shapefile | 20171215 2000Z Day 2 FireWX KML)

Day 2 Fire Weather Forecast graphic
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 17,493 11,799,036 San Jose, CA...San Francisco, CA...Oakland, CA...Stockton, CA...Glendale, CA...

Click for Day 2 FireWX Areal Outline Product (KWNSPFWFD2)

   FNUS22 KWNS 151958

   Day 2 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   0158 PM CST Fri Dec 15 2017

   Valid 161200Z - 171200Z


   Ongoing forecast is on track with minimal changes.  Widespread
   elevated to critical fire weather conditions are expected across
   much of California as strong northerly flow combines with 10-20% RH
   during peak heating hours.  Areas of dry fuels will support rapid
   fire spread with any fires that do develop.

   Farther east, the elevated area across the central/southern Plains
   has been expanded eastward a bit to include more of northeastern
   Oklahoma and adjacent portions of Kansas.  Current guidance only
   depicts minimum RH values at around 30% or so in these newly
   included areas, although some concern exists that deeper boundary
   layer mixing will result in lower RH values than currently expected.
   Winds across this area will gust above 20-25 mph at times during the

   See the previous discussion below for more information.

   ..Cook.. 12/15/2017

   .PREV DISCUSSION... /ISSUED 0106 AM CST Fri Dec 15 2017/

   Strong northerly deep-layer flow on the back side of an amplifying
   upper trough over the western U.S. will overspread much of the
   California on Saturday. At the surface, a cold front will move
   southeast across the Great Basin and high pressure will build over
   the region late in the period. Further east, a lee low will develop
   over the central High Plains and a tightening surface pressure
   gradient will aid in the development of breezy south/southwesterly
   winds across portions of the central and southern Plains. 

   ...Portions of Central into Northern CA...

   Elevated fire weather conditions will be widespread from the central
   coast into the Sacramento and portions of the San Joaquin Valleys as
   gusty north to northeast winds overspread the region and RH values
   fall into the 15-35 percent range. In the vicinity of the Bay Area
   mountains and foothills, critical fire weather conditions are
   expected to develop during the morning hours and continue into
   Sunday morning.  The strongest north winds are expected to align
   with lower RH values in this area. Sustained north/northeast winds
   of 20-30 mph with higher gusts will be possible in the mountains and
   foothills, where RH values will fall into the 15-25 percent range.
   Winds will remain gusty into the overnight hours and RH recovery
   will be poor in the mountains.

   ...Portions of Southern CA...

   As high pressure settles back into the Great Basin Saturday night,
   the pressure gradient will again become favorable for gusty offshore
   winds. Wind speeds are expected to increase across the L.A. and
   Ventura County mountains after dark and sustained speeds of 20-30
   mph with higher gusts are expected. RH values across the mountains
   will remain low, in the 10-20 percent range. As a result, critical
   fire weather conditions are expected to develop once again Saturday
   night into Sunday morning. 

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

   Breezy south/southwest winds are expected during the afternoon as a
   lee low develops over eastern CO. A dry airmass will be in place and
   warm afternoon temperatures resulting in boundary-layer mixing to
   around 2-3kft will allow for RH values falling into the 20-30
   percent range. Sustained wind speeds of 10-15 mph with higher gusts
   will result in widespread elevated to locally critical fire weather
   conditions during the afternoon.

   ...Please see for graphic product...


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