Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 13 2023 18:29:52

AWUS01 KWNH 131829
FFGMPD
AZZ000-NVZ000-CAZ000-140000-

Mesoscale Precipitation Discussion 0918
NWS Weather Prediction Center College Park MD
228 PM EDT Sun Aug 13 2023

Areas affected...Portions of northwest AZ...southern
NV...southeast CA

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

Valid 131825Z - 140000Z

Summary...Localized short-term totals of 1-3" (with as much as 1"
in as little as 15-min) could lead to isolated instances of flash
flooding (some significant).

Discussion...Scattered convection has developed across portions of
the Desert Southwest this afternoon, amid rather slow deep layer
flow (850-300 mb) of 5-15 kts. The mesoscale environment is
characterized by modest ML CAPE of 250-750 J/keg, PWATs of
0.9-1.3" (near the 90th percentile, per VEF/FGZ sounding
climatology), and minor diffluence aloft on the eastern periphery
of an upper-level low. These conditions have supported rather
impressive short-term totals (as indicated by MRMS) as high as
2-3" in an hour (with an inch in as little as 15-min). These
totals are highly localized with pulse-like convection likely
rapidly dying out, but the combination of slow storm motions and
weak diffluence aloft (amid anomalous tropospheric moisture) could
continue to support localized (and possibly significant) instances
of flash flooding through the late afternoon hours. Locations most
at risk of flash flooding include normally dry washes, burn scars,
and slot canyons. Rapid flash flooding may also occur over dry
locations just downstream of where extreme rainfall occurs, so
extra caution should be exercised by those outdoors in low-lying
areas.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_xxjS6ON-R4jJ-8JZYqapbGV8jd7WMqQvhCsAHHyo6Wy53kbVdJseVHOvPWgeuCbnY9F=
gSTNAguvepnm3Gj7pU8ni24$  for graphic product...

ATTN...WFO...FGZ...PSR...VEF...

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

LAT...LON   36781596 36741392 36521300 35801260 35131179=20
            33971185 34581357 34911513 35551650=20

=3D =3D =3D
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