651
FXUS65 KVEF 172150
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
250 PM PDT Wed Sep 17 2025

.KEY MESSAGES...

* Increasing tropical moisture will move into the region Thursday
  and Friday, bringing chances for showers and thunderstorms.
  Locally heavy rain and high rainfall rates will lead to an
  increased risk of flash flooding.

&&

.DISCUSSION...through Tuesday.

Current satellite imagery shows a batch of tropical moisture moving
towards the southern California Coast. Thunderstorms are ongoing in
northern Baja and the San Gabriel Mountains in California. This
moisture is expected to be pushed inland by an eastward moving
trough over the next two days, sending PWATs to over 200 percent of
normal for this time of year. Mid and high cloud cover will hinder
widespread convection across much of southern Nevada and
northwestern Arizona tomorrow. However, enough clearing behind the
cloud cover combined with ample moisture will create a favorable
environment for convection in the deserts of southeastern
California. Storm development begins in the morning after sunrise
and will last throughout the day and overnight. Mid and upper
level support and some training potential means that rain rates of
1 to 2 inches per hour are possible. Therefore, issued a Flood
Watch for San Bernardino County from 8 AM PDT Thursday to 2 AM PDT
on Friday. Friday should be less robust as the best forcing exits
the area, but lingering moisture and instability will leave an
active monsoonal environment. The area should gradually dry out
over the weekend and early next week. Temperatures will increase
next week and reach above average values by Tuesday.

&&

.AVIATION...For Harry Reid...For the 00Z Forecast Package...Light
and diurnal winds with speeds of less than 10 knots are expected
through most of the forecast period. Occasional gusts to around 15
knots are possible through the evening. Winds will become
southwesterly overnight, returning to the east-northeast Thursday
morning. Thunderstorm activity picks up in southern Nevada
Thursday afternoon, but confidence in timing and placement is low
at this time. BKN to SCT cloud cover moves in overnight, lasting
through tomorrow, with bases between 10 and 12 kft.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...Light and diurnal
winds are expected for most locations through the rest of today
and tonight. BKN mid and upper level cloud cover moves into the
area tonight and tomorrow. The greatest confidence for
thunderstorm activity tomorrow is in San Bernardino County
including KDAG. Convection may begin as early as 15Z and storms
may produce heavy downpours and gusty outflow winds. Additional
storms are possible in southern Nevada, but confidence in timing
and placement is low at this time.

&&

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

&&

$$

DISCUSSION/AVIATION...Meltzer


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NWS Flagstaff Office