593
FNUS21 KWNS 200657
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0156 AM CDT Wed Aug 20 2025

Valid 201200Z - 211200Z

...Synopsis...
A strong ridge of high pressure building over the central US is
forecast to gradually move west while a weak trough on the western
edge, suppresses the northern extent. The increasingly strong height
gradient along the western periphery of the ridge will bolster
mid-level winds aloft over the Northwest and northern Great Basin.
At the surface, a cold front will move into the western Great Basin
before stalling this afternoon. The front, and increased flow aloft
will support gusty surface winds and isolated storms, increasing
fire danger today and tonight.

...Great Basin...
Several hours of dry/breezy conditions are expected this afternoon
with the breakdown of the upper-level ridge. Very warm temperatures
are expected, supporting deep vertical mixing and low boundary-layer
RH. West/southwesterly winds of 15-20 mph with gusts of 20-30 mph
near the front, and RH below 15% on a widespread basis will support
elevated to locally critical fire-weather conditions from southern
ID into the Great Basin.

Increased southwesterly flow aloft on the western edge of the ridge
will help monsoon moisture (PWATs 0.6-0.8 inches) advect northward
over NV and western UT. The surface cold front associated with the
upper trough will stall over the western Great Basin, serving as a
focus for isolated thunderstorm development through the afternoon.
Uncertainty remains high regarding coverage of thunderstorms,
especially with southern extent. While moisture and instability will
be more limited, enough instability and forcing are expected to
produce isolated high-based showers and thunderstorms capable of dry
lightning. Should these storms develop they may track eastward,
persisting overnight into eastern ID and western MT with a continued
threat for dry strikes. Additionally, any active large wildfires may
have increased chances of deep pyroconvection/localized extreme fire
behavior given the steep lapse rates and unstable troposphere.

..Lyons.. 08/20/2025

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

$$