Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 19 2023 05:08:14

AWUS01 KWNH 190508
FFGMPD
AZZ000-NVZ000-CAZ000-191000-

Mesoscale Precipitation Discussion 0945
NWS Weather Prediction Center College Park MD
107 AM EDT Sat Aug 19 2023

Areas affected...portions of southeastern CA...much of
west-central AZ

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

Valid 190505Z - 191000Z

Summary...Localized rainfall rates of 1-2"/hr (with as much as 1"
in 15-min) to continue into the overnight hours. Isolated
instances of flash flooding will remain possible.

Discussion...Convection across the southwestern CONUS has
decreased substantially in coverage and intensity over the past
several hours, but isolated updrafts remain active across portions
of southeastern CA into west-central AZ. This localized activity
is expected to continue, given ample instability at this hour (per
MU CAPE of 1000-3000 J/kg, per SPC RAP analysis). Tropospheric
moisture content is also quite impressive well ahead of
approaching Hurricane Hilary, with PWATs of 0.9-1.8 inches
(between the 90th percentile and max moving average, per
YUM/FGZ/VEF sounding climatology). In addition to impressive
levels of instability and moisture, there is also equally
anomalous deep layer (0-6 km) wind shear of 20-40 kts (provided by
a negatively tilted upper-level trough along the central and
northern CA coast). This shear should continue to support updraft
longevity, with localized rainfall rates as high as 1-2"/hr (and
as much as 1" in only 15-min). As a result, isolated instances of
flash flooding will continue to be possible through much of the
overnight hours (gradually decreasing in coverage with additional
convective inhibition via a combination of growing cold pools and
radiational cooling). In the meantime, new convective activity
will be favored with cell mergers and outflow boundary collisions
(with the HREF-FV3 member handling ongoing and future expected
activity the best of all the CAMs).

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9NOe3y_Z7hMz9s8Ni5wAwAhaDUbW3CuNefZ8gaith4sXfsTt_cZa0K92G0tlk0cO20Af=
lbGs61aIpGfJYof_RAijOhs$  for graphic product...

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

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

LAT...LON   36971265 36871138 36031080 35201088 33811111=20
            32821164 31931251 31941400 32321487 32661540=20
            34411599 35241485 36231434 36851357=20

=3D =3D =3D
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