297
FXUS65 KVEF 020956
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
256 AM PDT Tue Sep 2 2025

.KEY MESSAGES...

* Monsoonal moisture surges into the forecast area today, resulting
  in widespread shower and thunderstorms capable of producing flash
  flooding.

* Moisture remains in place through midweek before slowly scouring
  out of the region, shifting precipitation chances further east
  each day.

&&


.DISCUSSION...Today through Monday.

The ridge of high pressure over the Desert Southwest will shift
slightly eastward today, as a result of a shortwave approach off the
California coast. This eastward shift will aid in monsoonal moisture
advection into our CWA today, due to the resultant southerly flow.
PWATs will range from 1.25 to 1.50 inches across our southern zones,
including San Bernardino County, Clark County, and southwestern
Mohave County. In addition to this moisture, an easterly wave will
rotate around the aforementioned high pressure to combine with the
incoming California shortwave. As this occurs, the resultant
vorticity lobe will push northward through southeastern California
this afternoon, providing necessary forcing for widespread
thunderstorms. Convection will initially favor the higher terrain,
as cloud cover may inhibit lift from daytime heating in valley
locations. With ample moisture and forcing, the primary threats
today will be moderate-to-heavy rain, frequent lightning, and flash
flooding. Best chances of widespread flash flooding exist across San
Bernardino County and Death Valley, where Flash Flood Watches are in
effect from 9 AM this morning through 1 AM PDT tonight.

Today`s vorticity lobe will weaken somewhat on Wednesday as it
shifts over south-central Nevada. Moisture will continue to inch
further north on Wednesday, with PWAT values across our southern
zones increasing to 1.50 to 1.75 inches. As such, expect widespread
showers and thunderstorms once again on Wednesday, with best chances
spreading further east. Thunderstorms on Wednesday will be
productive rain-makers, with high rain rates and instances of flash
flooding expected once again. Confidence regarding the location of
these storms is low at the moment, so the Flood Watch has not been
extended into Wednesday at this time. Moisture slowly scours
northwest-to-southeastward out of the region through the remainder
of the work week, with precipitation chances becoming more and more
confined to the eastern zones each day. Expect below-normal
temperatures through the forecast period, as a result.
&&


.AVIATION...For Harry Reid...For the 06Z Forecast Package...Quiet
weather is expected overnight into Tuesday morning. Winds will
likely become east to northeast by late morning, and could reach 10
knots on occasion. As noted by earlier shifts, morning clouds and
virga could influence afternoon thunderstorm development. The most
likely time for storms in the vicinity should be from mid afternoon
into the evening, with erratic gusty winds being the primary threat.
Briefly heavy rain and lower ceilings will also be possible.
Temperatures could exceed 100F between 22Z and 02Z, but will be
highly dependent on thunderstorms in the area.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Mostly quiet weather is
expected overnight, although some showers and possibly a
thunderstorm or two could break out in southern San Bernardino
County by morning. Thunderstorm coverage will increase around the
entire region in the afternoon and evening, with the main threats
being erratic gusty winds and briefly heavy rain with associated
lower ceilings and terrain obscuration. Some thunderstorms could
persist well into Tuesday night in San Bernardino County.
&&


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

&&

$$

DISCUSSION...Soulat
AVIATION...Morgan

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