Fire Weather Outlook Discussion
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365
FNUS21 KWNS 291640
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1039 AM CST Sun Nov 29 2020

Valid 291700Z - 301200Z

...Southern California...
The previous forecast remains on track. Morning surface observations
indicate elevated conditions ongoing across portions of southern CA,
with locally critical conditions noted across the higher terrain of
Ventura and Los Angeles Counties. Winds are expected to generally
diminish this afternoon as the pressure gradient weakens somewhat,
though RH values will still remain critically low. Some nocturnal
increase in winds is possible later tonight, which, combined with
poor RH recovery, will result in a continuation of elevated to
locally critical conditions into Monday morning.

...Western Kansas...
Locally elevated conditions will be possible this afternoon across
western KS within a dry/breezy post-frontal regime, though the
threat will be tempered to some extent by cool temperatures and
marginal RH values. See the previous discussion below for more
details.

..Dean.. 11/29/2020

.PREV DISCUSSION... /ISSUED 1240 AM CST Sun Nov 29 2020/

...Synopsis...
The upper-level flow regime is expected to amplify through the day
today, featuring a deepening trough across the eastern third of the
US and continued upper-level ridging over much of the West. A surge
of colder air and a strengthening surface high are expected across
the Plains that will bring gusty winds and perhaps brief fire
weather concerns for a few locations. Persistent offshore flow over
southwest California will continue to support elevated fire weather
conditions.

...Southern California...
Areas of elevated fire weather conditions are expected to continue
for today within the higher elevations of southern CA. Early morning
surface observations show pockets of elevated conditions ongoing
across the Santa Susana and western San Gabriel mountains. This is
mainly due to the maintenance of an offshore pressure gradient that
is associated with a surface high over the north/northeastern Great
Basin that is forecast to largely remain in place for most of today.
Poor overnight RH recoveries and little to no moisture return will
support another day of RH values in the low teens and single digits.
However, weak mid and upper-level winds will continue to limit the
potential for elevated and/or brief critical conditions to just
terrain-favored locations where winds may locally be stronger.

...Western Kansas...
Winds are expected to increase behind a southward surging cold front
later this afternoon across the Plains. Strong low-level cold
advection will aid in mixing down 30-40 mph 850 mb winds to the
surface across a broad swath of KS, OK, and the OK/TX Panhandles.
Despite this, most guidance suggests that the cooler air will limit
RH reductions for most of the region. A few locations across western
KS may see periodic RH reductions to near 20% due to slightly drier
air on the western periphery of the polar air mass. This idea is
supported somewhat by upstream post-frontal observations that show
dewpoints in the teens across the northern High Plains (versus 20-30
F dewpoints to the east). However, given little support by most
guidance, confidence in the coverage and duration of elevated fire
weather conditions remains low and precludes the addition of a risk
area.

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

$$



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