704
FNUS21 KWNS 121742
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1242 PM CDT Fri Jul 12 2024

Valid 121700Z - 131200Z

...CRITICAL FIRE WEATHER AREA FOR SOUTHEAST OREGON...FAR
NORTHWESTERN NEVADA...
...CRITICAL FIRE WEATHER AREA FOR EAST-CENTRAL IDAHO...

Elevated to Critical fire weather is expected across portions of the
Great Basin region into the Pacific Northwest, with windy/dry
conditions as well as several areas of isolated dry thunderstorms.

...East-Central Idaho (Snake River Plain)...
A Critical delineation was added into portions of east-central Idaho
within the Snake River Plain. Within this region, afternoon relative
humidity reductions to 10 percent will overlap sustained
west-southwest winds at 15-20 mph amid critically dry fuels.
Deterministic guidance is in agreement with this, as well as HREF
ensemble guidance which has a 70-80 percent probability of Critical
conditions being met for several hours in the late afternoon/early
evening.

The forecast for Critical conditions across southeastern Oregon into
far northwestern Nevada remains unchanged. Areas of isolated dry
thunderstorm activity across the Sierra Nevada and Arizona/Utah
Strip also remain unchanged with this outlook. See previous
discussion for more information.

..Thornton.. 07/12/2024

.PREV DISCUSSION... /ISSUED 0220 AM CDT Fri Jul 12 2024/

...Synopsis...
Fire weather concerns will continue today across portions of the
greater Great Basin region. Another day of very hot/dry conditions
is expected today as afternoon highs across much of the West climb
above 100 F. As of 05 UTC, single-digit RH values were noted across
much of the region with little, if any, improvement in surface
relative humidity anticipated over the next 24 hours. Despite the
hot/dry conditions, an upper ridge centered over southern NV will
continue to promote relatively benign winds for most locations, with
the exception of the northern Great Basin where gradient winds on
the periphery of the ridge will be slightly stronger. Isolated dry
thunderstorms will also pose a fire weather concern across parts of
the lower CO River Valley and along the Sierra Nevada.

...Southeast OR into southern WY...
A low-amplitude mid-level impulse is noted in early-morning
water-vapor imagery approaching the Pacific Northwest. Stronger
mid-level flow associated with this feature should overspread the
Cascades and northern Rockies through the day, leading to modest
surface pressure falls across eastern OR/WA into western ID as well
as along the northern High Plains. Low-level winds should strengthen
to between 15-20 mph within a belt stretching from southern OR into
southern ID and southern WY. Active fire behavior over the past 24
hours across east-central OR (even the absence of substantial winds)
suggests that fuels are very receptive to fire spread, so the
combination of very dry and breezy conditions will support elevated
to critical fire weather. A Critical risk area has been introduced
for portions of southeast OR into adjacent areas of northwest NV and
far northeast CA where ensemble guidance shows a reasonably strong
signal (70% probability in latest HREF and NBM guidance) for
sustained winds between 20-25 mph and the potential for gusts up to
35 mph.

...Lower CO River Valley into the Sierra Nevada...
00 UTC soundings sampled a plume of 0.5-0.9 inch precipitable water
values across the Four Corners region into southern CA. Recent GOES
imagery shows this plume gradually migrating west/northwestward
along the southern/southwestern side of the upper ridge. Steep
mid-level lapse rates across the region coupled with deep
boundary-layer mixing should support meager, but sufficient,
buoyancy for convection. Thunderstorm coverage should be fairly
isolated and tied to terrain features, as orographic ascent drives
thunderstorm development around peak heating. However, dry lightning
appears probable with any convection that can develop given the very
dry low-level conditions, and should pose a fire weather concern
given antecedent dry fuels.

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

$$