Graphic for MPD #0021

Mesoscale Precipitation Discussion 0021
NWS Weather Prediction Center College Park MD
342 PM EST Mon Jan 22 2024

Areas affected...Lower CO River Valley into southwestern AZ

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

Valid 222040Z - 230240Z

SUMMARY...Localized flash flooding will be possible through late
afternoon across portions of the Lower CO River Valley into
southwestern AZ. Slow moving areas of heavy rain with peak
rainfall rates of 0.5 to 1.5 in/hr are expected.

DISCUSSION...GOES West water vapor imagery showed a mid-level
vorticity max over the Imperial Valley of southern CA at 20Z,
tracking toward the east. This feature was located within the base
of a large scale, negatively tilted trough located over CA and was
associated with 1 to 2+ in/hr rates in San Diego earlier today.
While these same intensities are not expected over the Sonoran
Desert of eastern CA into western AZ, locally heavy rain and
possible flash flooding may still occur later this
afternoon/evening.

As the mid-level vorticity max continues toward the E/ENE through
03Z, a low level tap of moisture from the Gulf of CA into the
Lower CO Valley is expected. Marginal increases in instability, up
to 500 J/kg, are expected with the increased moisture into far
southeastern CA and southwestern AZ. A combination of low level
convergence near the vorticity max and increasing upper level
diffluence ahead of the upper trough axis will promote areas of
heavy rain with peak rainfall rates into the 0.5-1.5 in/hr range
and storm totals of 1 to 2+ inches. With minor exceptions, this
region of the country has been fairly dry over the past 1-2 weeks,
which should likely limit any excess runoff/flooding to relatively
impervious surfaces and low lying areas that poorly drain.

Otto

ATTN...WFO...FGZ...PSR...TWC...VEF...

ATTN...RFC...CBRFC...CNRFC...NWC...

LAT...LON   34801405 34751296 33871233 32981243 32321365
            32511500 32921552 33551567 34251552 34611487
           
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Last Updated: 342 PM EST Mon Jan 22 2024