441
AWUS01 KWNH 092101
FFGMPD
AZZ000-NVZ000-CAZ000-100200-

Mesoscale Precipitation Discussion 1173
NWS Weather Prediction Center College Park MD
501 PM EDT Thu Oct 09 2025

Areas affected...Southern Nevada...Southeast California...

Concerning...Heavy rainfall...Flash flooding possible

Valid 092100Z - 100200Z

SUMMARY...Training showers/thunderstorms capable of .5-.75"/hr and
localized streaks of 1-2" may result in localized flash flooding
over the next few hours.

DISCUSSION...CIRA LPW, VWP obs and RAP analysis, shows surge of
subtropical moisture through the Lower Colorado Valley on 15-20kst
of south to southeasterly confluent flow.  Total PWat values have
increased to over 1.25".  Strong convergence along the tight
moisture gradient has providing a sufficient differential boundary
for isentropic ascent.   Deep layer profiles are not particularly
unstable (100-250 J/kg of CAPE) given the mid-level warming, but
the strength of deep layer moisture convergence generally
coincident with a combined diffluent portion of the polar and
subtropical jet noted in GOES-W WV suite was sufficient to allow
for elevated convective cores to develop, maintain and even expand
upstream toward the San Bernadino Range.   Total Pwats of 1.25"
and moistening of the sub-cloud is allowing for some increased
rainfall rates of .5-.75"/hr.

Upstream shortwave energy rounding th western edge of the
sub-tropical ridge shows some additional cumuliform mid-level
clouds indicative of upstream energy and potential for further
upstream redevelopment/back-building environment. As such, with
deep layer steering generally oriented parallel to the ascent
boundary there is increasing potential for repeating cores and  a
streak or two of 1-2" totals.  Limited soil conditions and low FFG
values of .75-1.25"/3hrs suggests localized flash flooding is
possible within this band for the next few hours.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...SGX...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON   37971501 37571416 36171431 34711595 34491710
            35291750 37001667