Winchester, Nevada Weather Forecast Discussion

525
FXUS65 KVEF 162307
AFDVEF
Area Forecast Discussion
National Weather Service Las Vegas NV
407 PM PDT Tue Sep 16 2025
.KEY MESSAGES...
*Seasonably warm to hot and dry conditions to persist through
 midweek.
*Increasing moisture associated with the remnants of Mario will
 gradually move into the region, setting the stage for periods of
 showers and thunderstorms Thursday into the weekend. Heavy rain
 and high rainfall rates will lead to an increased risk of flash
 flooding.
&&
.DISCUSSION...
Elongated weak upper riding will continue to extend over the
region through tomorrow. This will generally promote dry
conditions and the continuation of summer-like temperatures near
to slightly above normal. This will begin to change late Wednesday
as upper and mid-level moisture begin to encroach from the south.
From Thursday into the weekend, short and medium range ensembles
point to gradually increasing moisture from south to north. This
is all associated with Mario, which is in the process of rapidly
weakening over the east Pacific. As a weak upper trough interacts
with and shears off this moisture, it will rapidly surge
northward, first along the California coast and areas inland.
However it will take more time to arrive across the deserts of
Southern California, Nevada, and Arizona, owing the mountainous
terrain upwind and orientation of upper flow. This will allow the
mid and upper atmosphere to moisten first, which will manifest as
rather expansive cloud cover. Despite rather impressive moisture
content, evident by PWATs on the order of 1-1.5 inches or better,
the abundance of clouds will act to limit daytime heating and
associated instability. While there will certainly be some shower
and at least isolated thunderstorm activity, this leads to a fair
amount of uncertainty with respect to thunderstorm coverage and
the attendant threat of flash flooding. Still, with any storms
that do manage to develop, rainfall rates of 2-3 inches per hour
can be expected given the tropical nature of the airmass in place.
Ensembles are in general agreement maintaining rather deep
moisture across the Desert Southwest at least into Saturday. The
EC ensemble holds onto this moisture a bit longer, and given the
general weakness of the upper trough, this appears to be a
reasonable solution, so expect Thursday afternoon through Saturday
to be the most active period for shower and thunderstorm
activity. From Sunday into next week, modest moisture will linger
with isolated terrain induced showers and storms each afternoon at
least into midweek. These look to be largely diurnal and will
likely diminish each night with the loss of daytime heating.
&&
.AVIATION...For Harry Reid...For the 00Z Forecast Package...Winds
will follow typical diurnal directional patterns with sustained
speeds of 10 knots or less. Southeasterly winds will continue into
the evening hours before swinging around to the southwest. Winds
will become light and variable during the early morning hours
before settling in from the east late tomorrow morning. High
clouds will begin to push into southern Nevada from the south
overnight tonight with mid-level clouds moving in tomorrow
evening. Temperatures are not expect to reach 100 degrees, but
will climb to the upper 90s between 22 and 00z.
For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...A mostly diurnal wind
pattern is expected at area terminals. Winds generally 10 knots
or less outside of KBIH and KDAG, where speeds and/or gusts to 15
knots can be expected at times. High clouds will gradually lift
northward across Southern California, Nevada and central Arizona
overnight into Wednesday. Low chances for scattered showers/storms
will enter the picture as early as late tomorrow afternoon mainly
for KDAG, KEED and KIFP. However, confidence remains rather low
in any terminal being directly impacted.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Austin
AVIATION...Stessman
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NWS VEF Office Area Forecast Discussion