Storm Prediction Center Day 1 Fire Weather Outlook
Created: Mon Dec 4 15:31:02 UTC 2017 (
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Storm Prediction Center Day 1 Fire Weather Outlook
Created: Mon Dec 4 15:31:02 UTC 2017 (
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Click for Day 1 FireWX Areal Outline Product
ZCZC SPCFWDDY1 ALL
FNUS21 KWNS 041530
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0930 AM CST Mon Dec 04 2017
Valid 041700Z - 051200Z
...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PARTS OF VENTURA AND LOS
ANGELES COUNTIES IN SOUTHERN CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...Portions of Southern CA...
Ongoing forecast is on track, no changes needed. Wind speeds were
already gusting to 40-50 mph in some locations with lighter winds in
lower elevations. Expect wind speeds to increase later today into
tonight with critical to extremely critical conditions developing by
this evening. See previous discussion below for further details.
...Portions of the Central/Southern Plains...
No changes needed, see previous discussion for details.
..Leitman.. 12/04/2017
.PREV DISCUSSION... /ISSUED 0150 AM CST Mon Dec 04 2017/
...Synopsis...
The primary upper trough over the northern Rockies/High Plains early
this morning will move east-northeastward across the northern Plains
into the Upper Midwest/Great Lakes region today. A positively tilted
trailing portion of this upper trough will remain over portions of
the Great Basin and Southwest through the period. At the surface, a
cold front will sweep southeastward across much of the
central/southern Plains as a low develops northeastward across the
Upper Midwest. Large-scale subsidence in the wake of the upper
trough will support a broad and strong surface high across the
northern Rockies and Great Basin. The surface pressure gradient
across southern CA will strengthen this evening into early Tuesday
morning, and high-end critical to extremely critical fire weather
conditions are expected across parts of this region.
...Portions of Southern CA...
Extremely critical area: A very strong surface pressure gradient
(evidenced by a LAX-DAG difference of -8 to -10 mb and LAX-TPH
difference of -15 to -20 mb) coupled with strong low-level
northeasterly flow will easily support sustained offshore winds of
30-40 mph across parts of Ventura into Los Angeles counties
beginning later this evening and continuing through early Tuesday
morning. Wind gusts of 60-80 mph will be possible across the
mountains/foothills of these counties where channeling and terrain
effects can locally enhance the already strong flow, with gusts of
45-60 mph likely at lower elevations. RH values will quickly plummet
below 10% later today, and will likely remain below 10% through the
end of the period owing to no overnight RH recovery given the
strength of the winds. Coupled with very dry and receptive fuels,
these expected meteorological conditions support the continuation
and eastward expansion of the extremely critical fire weather
delineation.
Critical area: Surrounding the extremely critical area, critical
fire weather conditions will occur across a broader part of coastal
southern CA today into tonight. RH values will rapidly fall to 5-15%
later this morning as diurnal heating and downslope warming/drying
act on an already dry airmass. Sustained winds of 20-30 mph will be
common across the critical delineation, with higher gusts of 40-60
mph likely, especially in higher terrain. Similar to the extremely
critical area, the pressure gradient across this region will be
strongest from late this evening through the end of the Day 1/Monday
period, and overnight RH recovery will be very poor.
Elevated area: Lower confidence in sustained winds in excess of 20
mph and/or sub-15% RH values exist across the elevated delineation
surrounding the critical area. However, winds will rapidly
strengthen across the mountains/foothills of southern CA, resulting
in a relatively tight gradient between elevated and critical fire
weather conditions.
...Portions of the Central/Southern Plains...
In the wake of the cold front mentioned above, strong/gusty
northwesterly winds of 20-30 mph will occur across much of KS into
OK, the TX/OK Panhandles, and eastern NM this afternoon and early
evening. Higher gusts up to 40 mph will be possible given the
strength of the mid-level flow that will likely be diurnally mixed
to the surface. With a dry airmass already in place across the
central/southern High Plains, RH values will likely become lowered
into the 15-25% range for at least a few hours behind the cold front
passage.
Some locally critical conditions may briefly occur across portions
of southern/central KS into western OK and the TX/OK Panhandles
immediately behind the front, where RH values may become critically
reduced. Still, latest guidance continues to suggest that these
conditions should occur for just an hour or two. Have therefore not
included a critical area at this time. Regardless, widespread
elevated conditions are anticipated across parts of the
central/southern Plains where generally dry/dormant fuels should
support large fire spread given the expected meteorological
conditions.
...Please see www.spc.noaa.gov/fire for graphic product...