Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Aug 21 2023 19:37:40

AWUS01 KWNH 211937
FFGMPD
AZZ000-UTZ000-220035-

Mesoscale Precipitation Discussion 0959
NWS Weather Prediction Center College Park MD
336 PM EDT Mon Aug 21 2023

Areas affected...Southwest UT...Far Northwest AZ

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

Valid 211935Z - 220035Z

SUMMARY...Some uptick in shower activity with somewhat heavier
rainfall rates can be expected over the next few hours. An
isolated threat of flash flooding will exist over the sensitive
slot canyons.

DISCUSSION...The latest radar imagery is showing a gradual
increase in shower activity across areas of northwest AZ and
southwest UT as a narrow. but confluent axis of deep tropical
moisture remains in place in a south to north fashion across
portions of the Southwest.

Daytime heating has allowed for MLCAPE values to locally reach up
to 500 to 1000 J/kg and this coupled with the deeper layer
southerly flow over the high terrain and related orographic ascent
will tend to favor additional convective development over the next
few hours, with some uptick in rainfall rates.

Some of the stronger convective cells that do materialize will be
capable of producing rainfall rates of 0.5" to 1"/hour and this
will be aided by some efficient warm rain processes given the
depth of the warm cloud layer.

The 12Z HREF guidance supports some additional 1.5 to 2+ inch
rainfall amounts through the late afternoon hours over areas of
especially southwest UT and far northwest AZ and this may result
in some concerns for isolated flash flooding or runoff problems
involving the sensitive slot canyons.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7nrCYgT7YOZ7QnPtvgC0govL6WJbZRSiSxLmqbE0FXIFS09kYSM_kvub9UH2zB1a89LK=
Gi2HSkTNup7gTwpZGADqlmc$  for graphic product...

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

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

LAT...LON   38601217 37741193 36651208 36531271 36881321=20
            37451338 38061334 38531299=20

=3D =3D =3D
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