Fire Weather Outlook Discussion
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FNUS22 KWNS 230649
FWDDY2

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0148 AM CDT Wed Aug 23 2017

Valid 241200Z - 251200Z

...Synopsis...
An upper trough/low will continue eastward across BC into AB and the
Pacific Northwest on Day 2/Thursday. Enhanced mid-level
west-southwesterly winds will overspread much of the northwestern
CONUS. At the surface, a cold front attendant to a low over
central/southern AB will sweep eastward across the interior Pacific
Northwest, northern Rockies, and northern High Plains through
Thursday night.

...Portions of the Interior Pacific Northwest into the Northern
Great Basin/Rockies: Isolated Dry Thunderstorm Threat...
Isolated to perhaps widely scattered thunderstorms should develop
Thursday afternoon from eastern OR into the northern Great
Basin/Rockies and adjacent High Plains as large-scale ascent
attendant to the previously mentioned upper trough overspreads these
regions. Precipitable water values generally 0.7-1.0 inch, dry
sub-cloud layers, and fast storm motions owing to the enhanced
mid-level winds associated with the upper trough should act to limit
wetting precipitation potential with this convection. Accordingly,
an isolated dry thunderstorm area has been introduced to account for
the threat of new lightning-induced fire starts where fuels are
dry/receptive. There may be some potential for greater (scattered)
thunderstorm coverage within the broad isolated dry thunderstorm
delineation. However, confidence in the location of this greater
coverage remains too low to include a scattered dry thunderstorm
area with this outlook.

...Portions of the Interior Pacific Northwest: Wind/RH Threat...
As the axis of the upper trough pivots over the Pacific Northwest,
strong/gusty low-level winds are forecast to develop across mainly
interior portions of WA/OR Thursday afternoon. Sustained westerly to
southwesterly winds of 15-20 mph appear likely behind the surface
cold front, with some channeling and localized higher gusts in the
eastern Columbia Basin. RH values are currently forecast to become
only marginally reduced, generally into the 15-20% range. However,
dry to very dry fuels and the expected meteorological conditions
will likely support elevated to locally critical fire weather
conditions across parts of central/eastern WA and northern OR
Thursday afternoon and evening.

...Portions of the Northern High Plains: Wind/RH Threat...
The surface pressure gradient will increase across the northern High
Plains on Day 2/Thursday between a deepening surface low over
central/southern AB and high pressure over ON and the Great Lakes. A
corresponding strengthening of low-level south-southeasterly winds
is expected across the northern High Plains in advance of the
previously mentioned cold front, with sustained surface winds of
15-20 mph probable. Moisture return should be rather limited across
this region owing to a prior frontal passage, and RH values may
become lowered into the 15-25% range Thursday afternoon across parts
of eastern MT and vicinity. With generally dry fuels across this
region, an elevated area has been introduced. The lack of an even
warmer/drier low-level airmass precludes a critical area at this
time.

..Gleason.. 08/23/2017

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

$$



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