545
AWUS01 KWNH 121905
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-130100-

Mesoscale Precipitation Discussion 1485
NWS Weather Prediction Center College Park MD
304 PM EDT Mon Oct 12 2026

Areas affected...central/southeastern NV, northwestern AZ into
central UT

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

Valid 121903Z - 130100Z

SUMMARY...A few areas of flash flooding will be possible through
the late afternoon/early evening across southeastern NV,
central/northwestern AZ into central UT. Peak hourly rainfall of
0.5 to 1.0 inches is expected.

DISCUSSION...Regional radar and visible satellite imagery has
shown a steady increase in the coverage and intensity of showers
across central AZ into southeastern NV/southwestern UT over the
past 2 hours ending at 1830Z. GLM imagery also noted some embedded
thunderstorms over southeastern NV at times. This activity was
located ahead of an eastward advancing mid to upper-level trough
axis extending from northwestern NV into southern CA (just west of
the Los Angeles metro). While precipitable water values have
lowered compared to 24 hours ago, they remain anomalous (+1 to +2
standard deviations above the mean) ahead of the upper trough axis
from the lower CO River Valley into northern AZ and much of UT.
Instability is weak however, with modest surface dewpoints in the
mid-40s to mid-50s and areas of cloud cover resulting in less than
500 J/kg MLCAPE area-wide via the 18Z SPC mesoanalysis.

Despite the weak instability, lift associated with the advancing
upper trough axis and the left-exit region of a RAP forecast upper
level jet streak from the CA/MX border into western AZ are
expected to help support the continued development of showers and
thunderstorms through the afternoon and early evening hours. RAP
forecast soundings show that dry air in the upper levels will
limit the vertical extent of any showers/thunderstorms that form
but flow will remain unidirectional from the southwest supporting
repeating and training segments of heavy rainfall. Continued
surface heating should allow for a few pockets of 500+ J/kg MLCAPE
to develop into the afternoon according to recent RAP forecasts.

Peak rainfall of 0.5 to 1.0 inches in an hour (or less than an
hour) are expected where southwest to northeast axes of heavy rain
setup. Flash flooding may result given widespread heavy rainfall
over the past 24-48 hours associated with Post-T.C. Rachel which
has increased soil moisture and stream/river levels. Areas of
flash flooding may result with slot canyons, sensitive burn scars,
small streams and normally dry washes at greatest risk for impacts.

Otto

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

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

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

LAT...LON   40091161 39761103 39201069 38131100 36361128
            35331106 34641068 34241055 33981065 33801083
            33651120 33591165 33741271 34211380 35231489
            36041552 37081564 37891526 38791469 39581367
            40081256