Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Aug 02 2023 20:04:22

AWUS01 KWNH 022004
FFGMPD
UTZ000-NVZ000-030200-

Mesoscale Precipitation Discussion 0840
NWS Weather Prediction Center College Park MD
403 PM EDT Wed Aug 02 2023

Areas affected...Central NV...Western UT

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

Valid 022000Z - 030200Z

SUMMARY...Dawdling storms over the Great Basin may cause areas of
flash flooding this afternoon and evening.

DISCUSSION...An upper level disturbance spiraling over eastern NV
is responsible for widespread strong storms over southern UT and
northern AZ. On the northern and western flank of the upper low,
RAP forecast show a convergence zone of 850-500mb streamlines over
northern NV that is helping to act as a source of lift for
developing thunderstorms. RAP forecasts show >1,000 J/kg of SBCAPE
over eastern NV with up to 1,500 J/kg in northwest UT. In
addition, moisture content is unusually high, ranging between
0.75-1.0" for most of the highlighted region. These values rank at
or slightly above the 90th climatological percentile according to
NAEFS.

The unstable air-mass and abundant atmospheric moisture is coupled
with very slow storm motions. Latest RAP forecast shows wind
speeds below 5 kts in east-central NV this afternoon. The lack of
vertical wind shear aloft means storms will be pulse-like, but
given the anomalous moisture and sufficient instability aloft,
storms could produce torrential downpours in short order before
dissipating. Outflow boundaries will also occur and likely will
spawn additional storms over the next several hours. The 12Z HREF
does suggest there are 20-25% odds of 1-hr QPF exceeding 1-hr FFGs
in east-central NV this afternoon. There are also some highly
sensitive soils along the NV/UT border with the AHPS showing as
much as 400-600% of normal rainfall over the past 7 days. Flash
flooding is possible this afternoon and into the evening hours.
Areas most at-risk are the aforementioned saturated soils within
the targeted region, as well as poor drainage areas and dry washes.

Mullinax

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!80fbDAh-dEAX_hEPvRHAjgaxj0o-nfaATxIlvEBQs2FV_tzxbY362iFHl6PPN9MAwVp5=
ZDvoG_ZT-cGcXItWrmVb-40$  for graphic product...

ATTN...WFO...LKN...REV...SLC...VEF...

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

LAT...LON   41951401 41371338 40681258 39821346 38551392=20
            38071432 37591565 37741670 38461744 39491770=20
            40281745 41341670 41801541=20

=3D =3D =3D
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