Fire Weather Outlook Discussion
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FNUS21 KWNS 240629
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0128 AM CDT Thu Aug 24 2017

Valid 241200Z - 251200Z

...CRITICAL FIRE WEATHER AREA FOR SCATTERED DRY THUNDERSTORMS ACROSS
PARTS OF NORTHEAST OR...CENTRAL ID...AND SOUTHWEST MT...

...Synopsis...
An upper trough/low will continue eastward across BC into AB and the
Pacific Northwest today. 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 tonight.

...Portions of the Interior Pacific Northwest into the Northern
Great Basin/Rockies: Dry Thunderstorm Threat...
Isolated to scattered thunderstorms will develop this 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 rainfall potential with this
convection. Accordingly, an isolated dry thunderstorm area has been
continued to account for the threat of new lightning-induced fire
starts where fuels are dry/receptive. A scattered dry thunderstorm
delineation also exists across parts of northeastern OR into central
ID and southwestern MT where a gradient in precipitable water values
will be present. Latest short-term guidance remains consistent in
showing this corridor as having the greatest convective coverage
this afternoon and evening.

...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 and far northern ID this afternoon.
Sustained westerly to southwesterly winds of 15-20 mph will occur
behind the surface cold front, with some channeling and localized
higher gusts in the eastern Columbia Basin. RH values are expected
to become only marginally reduced, generally into the 15-20% range.
However, dry to very dry fuels and the forecast meteorological
conditions will support elevated to locally critical conditions
across parts of central/eastern WA, northern OR, and the Panhandle
of ID this afternoon and evening.

...Portions of the Northern High Plains: Wind/RH Threat...
The surface pressure gradient will increase across the northern High
Plains today 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 by this afternoon across parts of
eastern MT and vicinity. With generally dry fuels across this
region, an elevated area has been maintained with no changes. The
lack of an even stronger forecast winds and a warmer/drier low-level
airmass continues to preclude a critical area.

..Gleason.. 08/24/2017

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

$$


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