Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
423 PM EDT Fri Aug 18 2023

Valid 00Z Sat Aug 19 2023 - 00Z Mon Aug 21 2023

...Hurricane Hilary to bring heavy rainfall and flash flooding to parts of
the Southwest this weekend...

...Critical fire conditions expected from the Northwest to the Northern
High Plains tonight...

...Dangerous heat redeveloping over the central U.S.....

Shortwave energy out ahead of Hurricane Hilary will generate scattered
showers and thunderstorms across the Desert Southwest, southern Sierra
Nevada and Central Great Basin tonight. The heaviest rainfall (~1 inch)
will occur along the U.S. Mexico border, but rain-sensitive areas in the
Southwest and Four Corners regions could experience flash flooding from
relatively lighter amounts. A Slight Risk of Excessive Rainfall leading to
Flash Flooding is in effect across southeastern California, southern
Nevada/Utah and northwestern Arizona through tonight. Dry conditions and
strong winds beneath the base of an energized upper trough will support
two targeted critical fire weather risk areas over parts of eastern
Washington/northern Oregon and northern Montana, respectively tonight.

Rain and thunderstorm activity associated with Hilary begin to ramp up
across the Desert Southwest on Saturday. A Moderate Risk of Excessive
Rainfall in effect for much of southeastern California, parts of western
Arizona and southern Nevada on Saturday due to potential flash flooding
concerns over sensitive burn scars, elevated terrain and slot canyons.
Winds and rain rates will intensify more across California and the
Southwest early Sunday morning into Monday, when the brunt of Hilary's
impacts will be felt. Rainfall amounts of 3 to 6 inches, with isolated
amounts of 10 inches, are expected across portions of southern California
and southern Nevada. Dangerous to locally catastrophic flooding will be
possible. Elsewhere across portion of the western United States, rainfall
totals of 1 to 3 inches are expected, resulting in localized flash
flooding. The deluge of rainfall could set records when all is said and
done. Record low maximum temperatures are also likely across the desert
Southwest on Sunday and Monday due to the abnormal lack of sunshine caused
by Hilary.

Dangerous heat will continue to intensify and expand into the Plains
states through Saturday, with numerous daily high temperature records
expected, especially in the Central Plains and Texas. The heat wave will
further expand on Sunday and early next week to include much of the
Central and Southeast U.S.. Some locations in the Midwest may see their
hottest day of the year so far this weekend, and portions of the
South-central U.S. and Gulf Coast may further extend their record number
of hours with a heat index reading of at least 110F degrees. The prolonged
nature of the heat wave combined with very warm overnight temperatures
will limit relief from the oppressive daytime heat and compound overall
heat impacts.
   
Kebede

Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php