Flash Flood Warning 222, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
211 PM PDT Tue Aug 23 2022

.SYNOPSIS... Monsoon moisture returns for much of the area on
southeast flow Wednesday, bringing increased thunderstorm chances
for Wednesday, Thursday, and possibly Friday. Another drying trend
is expected for the weekend.
&&

.SHORT TERM...through Friday. A few thunderstorms can be seen on
radar this afternoon as we near peak daytime heating. Convection
is having difficulty sustaining off the ridge tops. This makes
sense given a stout 500mb inversion seen on the 12Z Las Vegas
sounding. Weakening of an eastern Pacific ocean ridge will allow
deep monsoonal moisture to return in southeasterly flow.
Precipitable water will increase to around 1.5" which is near
record for this time of year and provides more than enough fuel
for storms with high rain rates. This will continue through
Thursday, wish residual moisture allowing for possibly another
active day Friday.

.LONG TERM...Friday through Tuesday.

Model ensembles indicate a dry westerly flow aloft beginning to
develop Friday over our region and continuing through the weekend
then becoming southwest as a mean trough develops off the West
Coast. This is reflected in the latest NBM gridded forecast which
indicates decreasing chances for thunderstorms Friday through the
weekend over southern Nevada and eastern San Bernardino County while
30-40 percent probabilities remain over much of Mohave County Friday
through Sunday. Moisture may not be entirely scoured out of the
region though the persistent drying effect continues Monday and
Tuesday with ensemble mean precipitable water values dropping to
less than one inch over all areas north of I-40 and PoP values
reducing to 10-20 percent over the mountains of southern Nevada and
northwest Arizona. Temperatures will also be subdued in this pattern
with highs near or slightly below normal which translates to highs
generally 98-103 across most desert zones.
&&

.AVIATION...For Harry Reid...Isolated thunderstorms are possible
once again this afternoon with the majority of the convective
activity remaining over the higher terrain surrounding the Vegas
valley.  The only impacts expected at the terminal from this
activity are outflow winds and only a low chance exists for that.
Outside of thunderstorm activity, light winds favoring typical
diurnal wind directions can be expected.  Monsoonal moisture
increases tomorrow likely resulting in an uptick in convective
activity near the terminal, most likely after 20Z.

For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated to scattered convection is expected once again
this afternoon, mainly over southeastern Nevada and northwest
Arizona after 21Z.  Gusty outflow winds, brief heavy rainfall, and
CIGs to 10kft will be the main impacts of this activity.  Convection
should quickly decrease after sunset.  Away from convection, winds
should remain light and favor typical diurnal variations.  Monsoonal
moisture looks to increase across the region tomorrow resulting in
an uptick in afternoon and evening thunderstorm activity.

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

SHORT TERM...Berc
LONG TERM...Adair
AVIATION...Planz

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