Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Aug 17 2023 22:01:47

AWUS01 KWNH 172201
FFGMPD
WYZ000-UTZ000-IDZ000-NVZ000-180253-

Mesoscale Precipitation Discussion 0939
NWS Weather Prediction Center College Park MD
600 PM EDT Thu Aug 17 2023

Areas affected...South-Central to Southeast ID...Northern UT...Far
Southwest WY

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

Valid 172153Z - 180253Z

SUMMARY...Scattered showers and thunderstorms with locally heavy
rainfall rates will foster concerns for at least some isolated
flash flooding going through the remainder of the afternoon hours.

DISCUSSION...The latest GOES-18 Day Convection RGB satellite
imagery shows some strong convection with enhanced updrafts and
corresponding rainfall rates impacting areas of northern UT near
the Wasatch and Uinta Range, and also over into adjacent areas of
far southwest WY. Areas of south-central to southeast ID likewise
are seeing stronger updrafts with radar imagery confirming
scattered areas of slow-moving showers and thunderstorms.

MLCAPE values of as much as 500 to 1000 J/kg are currently noted
over northern UT courtesy of strong diurnal heating, and this is
coupling with a substantial poleward advance of monsoonal moisture
from the Southwest U.S. to help drive convection with locally
heavy rainfall rates. The convection though is being strongly
facilitated by orographics with differential heating boundaries
and terrain-driven circulations playing a role in the convective
evolution.

The PWs across the region are quite anomalous, and reaching as
much as 3 standard deviations above normal with values of as much
as 1 to 1.2 inches. Some of the storms over the last couple of
hours have been producing some rainfall rates of 1 to 1.5
inches/hour based off GC-MRMS data.

Given the continued expansion of cooling convective tops over
areas of south-central to southeast ID and down into northern
UT/southwest WY adjacent to some of the higher terrain, there will
be concerns for some excessive rainfall amounts which may reach as
high as 2 to 3 inches where the slower moving cells tend to
persist. This may result in at least isolated instances of flash
flooding.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7YFW9dlHU47ZAfyRWTkNN1V0WODdphwiQZlIGtkPaDa3ocb3pgPSCV8Iu2YZR4JhC35q=
EXot70JtbB-OEZ9s7dLzqxE$  for graphic product...

ATTN...WFO...BOI...LKN...PIH...RIW...SLC...

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

LAT...LON   43271183 42981086 42211012 41171005 39741058=20
            39621152 39831217 40231229 40951227 41451272=20
            41561412 41831475 42361467 43061350=20

=3D =3D =3D
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