338
AWUS01 KWNH 302049
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-310245-

Mesoscale Precipitation Discussion 1533
NWS Weather Prediction Center College Park MD
448 PM EDT Fri Oct 30 2026

Areas affected...Lower Colorado River Valley into southwestern UT

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

Valid 302047Z - 310245Z

SUMMARY...A few areas of flash flooding will remain possible
across southern Nevada into adjacent areas of southwestern UT,
northwestern AZ and southeastern CA through ~03Z. High short term
rain rates of 0.5 to 1.0 inches in 15 minutes will be possible
with storm totals of 1 to 2 inches.

DISCUSSION...Trends in radar imagery over the past hour ending
2015Z have shown an increase in thunderstorm coverage from
southern NV into northwestern AZ and far eastern Riverside County
in southeastern CA. These cells were located underneath an upper
level trough with some degree of drier air moving over within the
upper levels. MLCAPE of 500 to 1000+ J/kg was estimated by the 20Z
SPC mesoanalysis from southern NV into the lower CO River Valley,
fueled by heating in the wake of thicker cloud cover advancing
downstream across the western UT/AZ border. Unidirectional
southwesterly flow in the LFC-EL layer has promoted training and
repeating of cells with observed 15-minute rainfall of 0.5 to 1.0
inches in Las Vegas and Henderson where precipitable water values
near 1 inch per recent GPS observations.

The reservoir of instability across southern NV into adjacent
portions of UT/AZ/CA is forecast to linger for at least another
3-6 hours with some waning of magnitude into the evening, but
remaining sufficient to support high short term rain rates for
several more hours. Destabilization downstream into southwestern
UT and portions of northwestern AZ remains uncertain, with the
highest rainfall rates possibly staying farther south over the
next few hours. The somewhat broad upper trough observed on water
vapor imagery across CA will continue the mean southwesterly flow
across the lower to middle CO River Valley well into the overnight
but the rainfall rates will be limited by the available
instability, which is expected to gradually diminish in the 00-03Z
time frame with the loss of surface heating. Therefore, while some
degree of convection should remain by 03Z, as well as a localized
flash flood threat, the threat is expected to reduce in coverage
beyond sunset.

Otto

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

ATTN...WFO...FGZ...PSR...SLC...VEF...

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

LAT...LON   37761337 37631292 37331254 36541252 35461303
            34201367 34421499 35591553 37041518 37741437