Tuesday, August 11, 2020

SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook Image
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0206 AM CDT Tue Aug 11 2020

Valid 111200Z - 121200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN WASHINGTON
AND NORTHERN OREGON...

...Synopsis...
A mid-level trough will amplify across the Pacific Northwest
throughout the period, with strengthening flow aloft overspreading a
warming/mixing boundary layer through the afternoon hours. The
stronger flow aloft is expected to mix down to the surface to
encourage dry and windy conditions supportive of wildfire spread
across portions of the Pacific Northwest and northern Rockies.
Large-scale lift associated with the mid-level trough is also
expected to support thunderstorm development within a west-east band
of mid-level moisture across the northern Great Basin into the
central Rockies, where dry lightning may also encourage new wildfire
ignitions. Finally, modest flow aloft associated with a small
impulse overspreading the southwest CONUS may also support surface
dry and windy conditions, where some wildfire spread potential may
be noted by afternoon peak heating.

...Pacific Northwest and parts of the Northern Rockies...
By afternoon, downslope along the lee of the Cascades will promote
at least 15 mph sustained westerly winds and 15-25% RH across much
of the Columbia and Harney Basins. High-resolution model guidance
continues to indicate Critical conditions (with 20 mph sustained
westerly winds) across southern parts of the Columbia Basin, along
the Washington/Oregon border, with a Critical area maintained.
Farther east in the Northern Rockies, downslope flow combined with
downward momentum transport, should contribute to widespread
Elevated conditions (15+ mph sustained westerly winds and 10-25% RH)
during the afternoon hours. Locally critical conditions may briefly
occur in the most terrain favoring locations, including the Snake
River Plain and Great Divide Basin. 

...Northern Great Basin into the Central Rockies...
With diurnal heating and increasing upper support, isolated to
potentially scattered thunderstorm development is expected,
especially to the lee of the Sierra in northern Nevada. Storms will
be high-based given a deep sub-cloud layer. Training storms and slow
storm speeds may allow for some localized appreciable rainfall
accumulations, precluding a scattered dry thunderstorm upgrade.
Farther east, along the aforementioned band of mid-level moisture,
isolated dry thunderstorms are expected as far east as central
Wyoming. Aforementioned dry/windy conditions across Wyoming may
serve to aggravate fire starts associated with dry strikes.

...Portions of the Southwest CONUS...
Guidance continues to indicate widespread Elevated to locally
Critical dry/windy surface conditions across southwest portions of
the Colorado Plateau, with 15-20 mph sustained southwesterly winds
overlapping with 10-20% RH for at least a few hours during the
afternoon. The primary negating factor in upgrading to Critical is
the lack of more discernible upper-support.

..Squitieri.. 08/11/2020

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

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/fire_wx/fwdy1.html

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