AWUS01 KWNH 041822
FFGMPD
COZ000-NMZ000-AZZ000-UTZ000-NVZ000-050020-

Mesoscale Precipitation Discussion 0803
NWS Weather Prediction Center College Park MD
221 PM EDT Sun Aug 04 2024

Areas affected...Western NM...Much of AZ...Central and Southern UT

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

Valid 041820Z - 050020Z

SUMMARY...Scattered monsoonal showers and thunderstorms are
expected today which will be capable of locally heavy rainfall
amounts and some isolated instances of flash flooding.

DISCUSSION...The midday GOES-E Day Cloud Phase RGB satellite
imagery shows convection initiating and beginning to gradually
expand in coverage across the higher terrain of western NM through
central AZ and northward up into southern and central UT.

This corridor is where there is still a rather decent
concentration of deeper layer monsoonal moisture which is
supporting PW anomalies of 1 to 2 standard deviations above
normal. A look at the latest CIRA-ALPW data shows the best
concentrations of this moisture pooled up over northern AZ through
southern and central UT around the western flank of the deeper
layer subtropical ridge centered over southern CO. Meanwhile,
SBCAPE values are locally as high as 1000 to 1500 J/kg, and strong
diurnal heating will contribute to a further increase in
surface-based instability over the next several hours heading
through the afternoon hours.

The favorable thermodynamic environment coupled with differential
heating boundaries and orographics/upslope flow around the higher
terrain will favor a further increase in the coverage of showers
and thunderstorms, and locally very heavy rainfall rates are
expected once again. Some of the stronger storms may result in
some hourly 1 to 2 inch totals, much of which may fall in as
little as 30 to 45 minutes. Some localized persistence of these
storms given rather slow cell-motions may yield potentially some
storm totals as high as 2 to 3+ inches.

Isolated areas of flash flooding will be possible given the
heavier rainfall rates, and this may cause impacts in particular
to some of the area slot canyons, burn scar locations and the
normally dry washes.

Orrison

ATTN...WFO...ABQ...EPZ...FGZ...GJT...PSR...SLC...TWC...VEF...

ATTN...RFC...CBRFC...WGRFC...NWC...

LAT...LON   39971006 39340893 37080879 36070844 35380789 
            34350735 33030739 32290791 31120958 31171138 
            31811221 33821278 34821406 36351412 37681364 
            39571190 
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