603
FNUS21 KWNS 200719
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0219 AM CDT Sat Jul 20 2024

Valid 201200Z - 211200Z

...Synopsis...
A large upper ridge will dominate the western US through the
forecast period within a relatively stagnant mid-level flow pattern.
A broad Pacific trough will move onshore to the west of the ridge,
bringing isolated thunderstorms to portions of the Northwest. To the
east, northwesterly flow aloft will continue over the northern
Rockies and Intermountain west with seasonable monsoon moisture.
Widely scattered thunderstorms are likely through the afternoon.

...Northern Great Basin and Northwest...
To the west of the upper ridge, subtle ascent will gradually
overspread portions of the northern Great Basin and Pacific
Northwest ahead of the advancing upper trough. PWAT values are
forecast to increase through the day, reaching 0.8 to 1 inches by
this evening. Continued moisture advection should allow for gradual
mid-level destabilization and dry thunderstorm development along the
higher terrain by mid afternoon.

Isolated thunderstorms over the northern Great Basin should slowly
expand in coverage to the northwest from late in the afternoon and
into the overnight period. Enhanced flow aloft will allow for
moderate storm motions of 20-25 kt atop relatively dry boundary
layer. This will likely support dry thunderstorm potential through
the overnight hours despite increasing mid-level moisture. Given the
potential for lightning over very receptive fuels (95th percentile
ERCs), the ISODRYT area was expanded westward into portions of
west/southwest OR.

...Northern Rockies...
East of the ridge, confidence in dry storms is lower, as flow aloft
will be weaker and deeper monsoonal moisture is expected to be in
place. The combination of slower speeds and higher PWATs suggests
storms may have greater rainfall efficiency. Still, the potential
for lighting outside of the wetter cores from scattered storm
coverage, and the possibility of a few drier storms, suggest some
threat for lightning ignitions. However, the best storm coverage
appears displaced to the east, away from the more receptive fuels.

..Lyons.. 07/20/2024

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

$$