Flash Flood in California, August 2, 2023

Area Forecast Discussion
National Weather Service Las Vegas NV
207 AM PDT Wed Aug 2 2023

.SYNOPSIS...Shower and thunderstorm activity across our west and
central areas this morning is forecast to shift into Lincoln and
Mohave counties this afternoon where moist and weakly unstable
conditions are focused. A few storms could linger over mainly
Lincoln County on Thursday before shower and thunderstorm chances
end Friday and over the weekend. Temperatures warm to near normal
late this week and slightly above normal over the weekend.

&&

.SHORT TERM...Today through Friday.

Monday ended up being several degrees cooler than forecast with
high temperatures around 10 degrees below normal. MRMS 24-hour QPE
shows a fairly typical monsoon day ranging from nothing to deluge
depending on where the stronger thunderstorm cells developed.
The mos notable high precip areas based on this QPE map included
the Sheep Range, Spring Mountains, Red Rock Canyon area into
northwest Las Vegas. Other isolated areas stand out including
along Interstate 40 east of Kingman and near Mountain Pass, and
east of Interstate 15 near Primm and Jean. At 2 am this morning,
radar indicated ongoing shower activity between Barstow and Baker,
in Yucca Valley, across the southeastern parts of Death Valley,
and in western Clark County with a few isolated thunderstorms
over east central Nye and west central Lincoln counties.

Hires models forecast expanding coverage of storms as we approach
daybreak and continuing through the morning hours. The focus
areas for scattered to numerous storms shifts to mainly Lincoln
and Mohave counties this afternoon with isolated storms west of
these areas. We should see some afternoon breezes develop
especially in the Western Mojave Desert up into the southern
portions of Inyo County. Skies will also clear across our western
and southern areas by this afternoon.

It is worth noting that yesterday began the slow August decent in
the average high temperatures in Las Vegas. It begins August 1st
at 104 degrees and falls to 100 degrees on the last day of of
month. We should generally see an increase in temperatures today
but they will remain below seasonal normals.

Thursday and Friday will be mainly dry with the exception of a few
isolated showers/storms in northern Lincoln and northern Mohave
counties. Slightly warmer temperatures are expected with highs
closer to normal. The lower desert locations see a return to
moderate heat risk but issuing any heat-related headlines looks
unnecessary at this point.

.LONG TERM...This Weekend into Next Week...

All ensembles point to high confidence (90-100%) in the return of
an extended period of hot dry weather. This will occur as upper
troughing intensifies across the Great Lakes Region, allowing a
broad elongated ridge of high pressure to extend from Southern
California eastward to the Gulf Coast. The result will be a dry
westerly flow, and with increasing heights and subsidence, we can
expect it to get hot again. In fact, a return of high temperatures
in the 105 to 110 degree range appears probable in the Las Vegas
Valley (60-90%), with a 40-50% chance of highs exceeding 120 in
Death Valley. The hottest days appear to be Saturday through
Tuesday.

Beyond midweek, ensembles, including the National Blend of Models,
hint that the upper ridge may move to a more favorable position for
a return of some monsoonal moisture. However, confidence remains low
at this timeframe.

&&

.AVIATION...For Harry Reid...Another round of showers and
thunderstorms expected this morning, with best chances between 14
and 17Z. Storms will be approaching from the west, so winds will
become west-southwesterly through this time with speeds generally
between 15 and 20 kts with gusts to 30 kts. Through the remainder of
the morning and afternoon, skies will clear, and winds will fall
into diurnal trends, with light southeasterly winds through the
afternoon and light southwesterly winds after sunset. Smoke output
from the York Fire has reduced, but reduction in surface and slant
visibility are still possible at times through the TAF period.

For the rest of southern Nevada, northwestern Arizona, and
southeastern California...A line of storms extending from KDAG
through KDRA to KTPH will start to organize around 09Z before
pushing eastward across the forecast area through the remainder of
the morning. Las Vegas Valley TAF sites will experience showers &
vicinity thunderstorms between 14 and 17Z, with west-southwest gusts
to 30 kts. Best chances for vicinity thunderstorms and related gusts
for KEED and KIFP will be between 15 and 18Z. Skies will clear
through the remainder of the afternoon, with TAF sites returning to
general diurnal trends. Smoke output from the York Fire has reduced,
but reduction in surface and slant visibility are still possible at
times through the TAF period.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.

&&

SHORT TERM...Salmen
LONG TERM...Austin
AVIATION...Varian

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