Fire Weather Outlook Discussion
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FNUS21 KWNS 211654
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1153 AM CDT Sat Oct 21 2017

Valid 211700Z - 221200Z

...CRITICAL FIRE WEATHER AREA FOR COASTAL RANGES OF SOUTHERN
CALIFORNIA...

...Coastal Ranges of Southern California...
Ongoing forecast of critical fire weather conditions for the
mountains of Santa Barbara, Ventura, and Los Angeles Counties in
southern California remains on track with no changes needed (see
previous discussion below for more details).

...Portions of the High Plains...
Despite relatively cool surface temperatures across this region,
windy and dry conditions will lead to elevated fire weather concerns
(see previous discussion for more details).  The only change was
extend the elevated area westward in Colorado where strong
northwesterly surface winds will contribute to warming and drying
through downslope effects.

...Lower Colorado River Valley...
An elevated area was added across the Lower Colorado River Valley,
where a favorably oriented surface pressure gradient will lead to
strong sustained northerly surface winds of 15-20 mph, especially
through the early afternoon.  As boundary layer deepening/mixing
occurs, RH values will fall below 15% resulting in elevated fire
weather conditions.

..Jirak.. 10/21/2017

.PREV DISCUSSION... /ISSUED 0131 AM CDT Sat Oct 21 2017/

...Synopsis...
A powerful mid-level trough will progress steadily eastward across
the center of the country today.  Upstream of this trough, mid/upper
ridging will develop across California and adjacent areas of the
Desert Southwest, while strong, zonally oriented mid-level flow
develops across the Pacific Northwest and northern Rockies.

At the surface, a lee trough and cold front will merge and make
eastward progress across the Plains, extending from the eastern
Dakotas southward to the Texas Panhandle by mid-afternoon.
Upstream, an expansive anticyclone will build into the Great Basin,
with 1030mb centered over western Colorado.  Each of these surface
features will foster fire weather concerns Saturday in the High
Plains and in southern California.

...Coastal Ranges of Southern California...
A synoptically evident fire weather scenario will unfold today as
high pressure in the Great Basin fosters a favorable surface
pressure gradient for gusty offshore winds.  Northeasterly surface
flow (with gusts as high as 50 mph) will develop especially in
terrain-favored areas and persist throughout the day.  By
mid-afternoon, very warm surface temperatures (approaching 90F) will
combine with RH values falling to around 10-15% to foster widespread
areas of elevated to critical fire weather conditions.  Critical
thresholds are most likely in portions of Santa Barbara, Ventura,
and Los Angeles Counties in southern California during the afternoon
and evening hours.  Overnight recoveries will be poor, and gusty
northeasterly winds will likely persist into Sunday.

...A large part of the High Plains from eastern Colorado northward
to southeastern Montana...
Although surface temperatures will be substantially cooler than in
previous days, continued westerly/downslope flow west of the lee
trough/cold front will maintain a very dry airmass across the
region.  RH will fall to around 10-15% in portions of eastern
Colorado, and near 20% across portions of southeastern Montana,
southwestern South Dakota, and vicinity.  Wind speeds will generally
fall below critical thresholds in most areas (around 15 mph with a
few higher gusts), although fuels appear to be capable of supporting
fire spread.  An elevated fire delineation remains in place across
this region to address the threat.

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

$$



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