447
FNUS22 KWNS 191907
FWDDY2

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0206 PM CDT Fri Jul 19 2024

Valid 201200Z - 211200Z

The previous forecast remains largely on track, with the potential
for isolated dry thunderstorms Day 2/Saturday afternoon into the
overnight across portions of the Northwest into the Great Basin and
northern Rockies. Primary change with this forecast was to expand
the Isolated dry thunderstorm area further northwest along and west
of the Cascades in Oregon, with ensemble guidance now suggesting
greater coverage of isolated fast-moving nocturnal thunderstorms.
Additionally, ERCs exceed the 97th percentile across much of the
area, likely leading to efficient lightning ignitions with any dry
thunderstorms. The isolated dry thunderstorm area may need to be
expanded even further northwestward toward the Oregon Coast, but
confidence remains a bit too low at this time.

Please see the previous discussion below for more information on
tomorrow`s fire weather forecast.

..Elliott.. 07/19/2024

.PREV DISCUSSION... /ISSUED 0205 AM CDT Fri Jul 19 2024/

...Synopsis...
An upper ridge over the western Rockies will persist D2/Saturday as
a broad Pacific trough moves onshore over the Northwest. To the
east, northwesterly flow aloft will continue over the northern
Rockies and Intermountain west, with seasonable monsoon moisture.
Widely scattered thunderstorms appear likely through the afternoon
with a risk for lightning within dry fuels.

...Northwest into the Great Basin and northern Rockies...
With the approach of the West Coast trough, weak ascent will allow
for isolated thunderstorm development along the higher terrain of
the Sierra and Cascades by early afternoon. Initial PWAT values of
0.8 to 1 inches will favor drier storm over areas of significantly
dry fuels and recent fire activity.

Storm coverage may increase overnight as the upper trough continues
onshore and ascent increases. While PWATs should also increase above
1 inch with onshore flow, faster storm motions will tend to limit
wetting rainfall, favoring drier storms. While confidence in
convective evolution toward the end of the period is lower, some
guidance suggests the largest increase in storm coverage after dark
may be focused west of the Cascades toward the coastal ranges of OR
and northern CA.

Farther east into the Great Basin and northern Rockies, confidence
in dry storms is somewhat lower. Flow aloft along the eastern
periphery of the ridge will be weaker with deeper monsoonal moisture
in place. The combination of slower storm 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 within mostly receptive fuels.

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

$$