Fire Weather Outlook Discussion
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000
FNUS22 KWNS 201730
FWDDY2

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1229 PM CDT Fri Oct 20 2017

Valid 211200Z - 221200Z

...CRITICAL FIRE WEATHER AREA FOR THE SANTA BARBARA...VENTURA...AND
LOS ANGELES COUNTY MOUNTAINS IN SOUTHERN CA...

...Southern California...
Critical fire weather conditions are still anticipated across the
mountains of Santa Barbara, Ventura, and Los Angeles counties from
late Saturday afternoon through Sunday morning. This will signal the
beginning of a prolonged period of critical fire weather conditions
where offshore flow will contribute to very warm temperatures, gusty
winds, and poor overnight RH recovery. Warm and dry conditions will
support elevated fire weather conditions elsewhere across the
region.

...Central High Plains...
High temperatures will be 20 to 30 degrees cooler on Saturday than
Friday but a dry, post-frontal airmass will still support low RH
values (from 15% to 25%) during the afternoon. The lowest RH values
are expected across northeast CO and adjacent portions of the NE
Panhandle. Gusty northwest winds in tandem with these dry conditions
and at least marginally favorable fuels will result in elevated fire
weather conditions.

..Mosier.. 10/20/2017

.PREV DISCUSSION... /ISSUED 0258 AM CDT Fri Oct 20 2017/

...Synopsis...
A powerful mid/upper trough will continue to migrate eastward into
the Great Plains Saturday while spreading strong, cyclonically
curved mid-level flow in much of the western and central CONUS.
This flow will flatten some across the Pacific Northwest but remain
strong as shortwave ridging develops across California and vicinity.
At the surface, a well-established lee trough and cold front will
migrate eastward across the central and northern Plains, with
surface flow remaining enhanced due to a strong pressure gradient.
Meanwhile, strong (1026 mb) high pressure will build into the Great
Basin, creating a synoptically evident fire weather scenario for
portions of southern California.

...Coastal Ranges of Southern California...
The aforementioned surface high will aid in strengthening an
offshore pressure gradient, resulting in areas of 20-25 mph
northeasterly surface winds with higher gusts.  These surface winds
are expected to be strongest in portions of Santa Barbara, Ventura,
and Los Angeles counties.  Meanwhile, insolation and downslope will
foster areas of very warm (70s and 80s F) surface temperatures along
with 12-25% RH values.  The combination of these atmospheric
conditions and areas of dry fuels will foster elevated to critical
fire weather conditions across much of the region during the
afternoon and evening.  Overnight recovery should also remain poor,
with locally elevated fire weather conditions expected to persist
overnight.

...Eastern Wyoming, southeastern Montana, western South Dakota, and
northwestern Nebraska...
Surface temperatures will be substantially cooler during peak
heating periods compared to D1/Fri, with high temperatures expected
to reach the 50s F and low 60s F.  Nevertheless, a continued dry
airmass will filter into the region, fostering 15-25% RH values
during the afternoon in conjunction with surface winds approaching
30 mph in a few areas.  Although areas of showers (and perhaps an
isolated thunderstorm) may traverse the region early D2/Saturday,
the expectation is that fuels across most of the region will remain
dry and support fire spread given expected afternoon conditions.
Thus, an elevated fire weather delineation has been introduced, with
locally critical conditions possible especially in southeastern
Montana.

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

$$



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