Fire Weather Outlook Discussion
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FNUS21 KWNS 261542
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1041 AM CDT Tue Sep 26 2017

Valid 261700Z - 271200Z

Ongoing forecast is on track and no changes are needed.  See
discussion below for more details.

..Leitman.. 09/26/2017

.PREV DISCUSSION... /ISSUED 0158 AM CDT Tue Sep 26 2017/

...Synopsis...
A highly amplified upper-level trough located over the western CONUS
is forecast to weaken throughout the day, with an upper-level low
developing in the vicinity of the lower CO River Valley, coincident
with the development of an upper-level ridge in the Pacific
Northwest.  These features should help to sustain modestly enhanced
northerly mid- to upper-level flow of 35-45 kt over much of CA.
Surface high pressure is forecast to be present over portions of the
Pacific Northwest and Great Basin regions along with warm/dry
conditions.

....Portions of the Sacramento Valley and Adjacent Coastal Ranges of
Northern CA...
Elevated fire-weather conditions are likely this afternoon across
portions of the Sacramento Valley and adjacent Coastal Ranges of
northern CA. Diurnal heating and vertical mixing should promote an
increase in northerly surface wind speeds approaching 15 mph along
with RH values decreasing into the 10-20% range, supporting an
elevated designation across this region.

....Portions of Southern CA...
Elevated fire-weather conditions should continue to develop across
portions of southern CA throughout the early morning today, with
less favorable conditions expected throughout the afternoon and
evening as the surface pressure gradient relaxes somewhat. These
elevated fire-weather conditions may redevelop early Wednesday
morning. A modest surface pressure gradient is developing early this
morning, bringing sustained offshore surface winds around 15-20 mph
across portions of the area, with stronger gusts up to 25-30 mph
occurring in the mountains/foothills. Several 06Z surface
observations in this region are already exhibiting elevated
fire-weather conditions, with RH values falling near or just below
20%. Locally critical fire-weather conditions may occur for a brief
period this morning mainly in higher terrain, given the combination
of strong winds approaching 20 mph, RH values becoming minimized
around 10-15%, and dry fuels. However, these conditions are not
expected to occur for more than 3 continuous hours on any more than
an isolated basis. Therefore, no critical area has been introduced.

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

$$


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