Flash Flood Warning 40, NWS Hanford, CA

Area Forecast Discussion
National Weather Service Hanford CA
1224 PM PDT Sat Aug 19 2023

.SYNOPSIS...
Strong thunderstorms across Central California are possible today
associated with moisture ahead of Hurricane Hillary. More
widespread precipitation is forecast for tomorrow, especially in
Tulare and Kern County -- including the Mojave Desert -- where
catastrophic flash flooding is conceivable. Rainfall associated
with Hilary will mostly exit the region by late Monday. A few
residual showers and thunderstorms in the Sierra Nevada are
forecast through the end of the work week.

&&

.DISCUSSION...
All eyes are currently on Major Hurricane Hilary, which is still
south of the forecast area, but impacts begin today. Moisture
associated with TC Hilary coupled with hot surface temperatures
will provide enough instability to support strong thunderstorms. A
severe thunderstorm or two today cannot be ruled out, with the
main hazard being strong downdraft winds. We have been included in
a rare "Marginal" Risk by the Storm Prediction Center for just
about the entire forecast area. The risk for severe weather will
decrease when the sun goes down later this evening. However, the
flood thread will continue to increase through the night.
Additionally, breezy conditions through the Grapevine and Highway
58 at the south end of the valley today may lead to some blowing
dust.

Once the isolated thunderstorm risk wanes tonight, the broader
rain shield will move over the area. This precipitation shield
will grow in coverage through the night and morning hours
tomorrow. There is a risk for heavy rain bands associated with
Hilary that have catastrophic flash flooding potential due to the
unusually potent moisture source that is associated with Hilary in
the Mojave Desert. The Weather Prediction Center has put the
desert area of Kern County in a very, very rare "High Risk" for
excessive rainfall on Sunday.

The high desert in Kern County will be really under the gun in
terms of flash flooding potential later tomorrow morning through
the evening hours as abundant moisture associated with Hilary
pushes inland. Flooding potential extends both north and west of
the desert tomorrow... flooding in locations such as Bakersfield
and Kernville cannot be ruled out, as well as foothill and
mountain locations in Tulare County. The main circulation
associated with Hilary will exit the region later on Monday, which
is when the heaviest rainfall and our Flood Watch are set to
expire. Once things are all said and done, the wettest locations
in the Mojave Desert in Kern County may see 4-5 inches of rain
through Monday.

Residual moisture will linger over the High Sierra through the
rest of the week. This will lead to thunderstorm potential through
the end of next week, but will be isolated in nature compared to
the showers and storms associated with Hilary.

&&

.AVIATION...
Areas of MVFR and local mountain obscuring IFR conditions in and
near showers and thunderstorms in the Sierra Nevada and adjacent
foothills after Saturday 19z. Showers and thunderstorms will also
impact the Kern County desert with areas of MVFR after Saturday
19Z. Otherwise, VFR conditions will prevail through at least the
next 24 hours.

&&

.AIR QUALITY ISSUES...
ISSUED:  08/18/2023 14:47
EXPIRES: 08/19/2023 23:59
None.

&&

.CERTAINTY...

The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday evening for CAZ314-316-322-328>339.

&&

ab

weather.gov/hanford

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