Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Sep 13 2023 21:23:05

AWUS01 KWNH 132122
FFGMPD
AZZ000-UTZ000-NVZ000-140315-

Mesoscale Precipitation Discussion 1067
NWS Weather Prediction Center College Park MD
522 PM EDT Wed Sep 13 2023

Areas affected...central/northern AZ, southeastern NV,
southwestern UT

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

Valid 132119Z - 140315Z

Summary...A couple of isolated areas of flash flooding will be
possible over the next 3-6 hours from central to northern AZ into
southeastern NV and southwestern UT. Rainfall rates between 1 and
2 inches in 15-30 minutes can be expected with the strongest cells.

Discussion...21Z regional radar imagery across the Desert
Southwest showed scattered thunderstorms stretching from
central/northern AZ into southeastern NV and southern UT. The
region was characterized by MLCAPE of 500 to 1000+ J/kg and
anomalous precipitable water values ranging from 0.8 to 1.1 inches
via 21Z SPC mesoanalysis data. 700 mb VAD wind plots helped
identify a low just west of the AZ border in eastern CA, and a
weak ridge over northwestern AZ. A downstream confluence axis
located near or just below 700 mb was noted over the southern
Colorado Plateau, roughly parallel to mean westerly flow present
in the 850-300 mb layer. Farther back to the west, slow moving and
training cells were observed from northwestern AZ into
southeastern NV where 850-300 mb mean winds were less than 10 kt,
supporting slow movement.

Thunderstorms will continue for at least another few hours within
the available pool of instability with elements of training where
outflow boundaries and/or cells line up with the mean steering
flow. One area where a short term flash flood threat will continue
is near an outflow boundary located in southern Navajo and
southeastern Coconino counties. Additional slow moving cells with
new development will also be possible from northwestern AZ into
southern NV until instability drops off after sunset with the loss
of heating. Repeating and training of heavy rain will have the
potential to produce high rainfall rates with 1-2 inches in 15-30
minutes. These rains may produce localized areas of flash flooding
with a focus on typical narrow canyons, normally dry washes and
any burn scars.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!93cSRQGMMcDVd681SPReJ6i8bHSj35q4exOpkWjCJf9ysR9ytz7Wg2ChNW7ZEqrIqrOR=
rp7KfAZeO3Q4BOmlZC8CET4$  for graphic product...

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

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

LAT...LON   37941319 37921262 37531202 36841175 36181127=20
            35631020 35010964 34050995 33931113 34391297=20
            34921453 35891566 36551601 37101599 37681532=20
            37911421=20

=3D =3D =3D
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