Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Jul 15 2024 21:10:09

AWUS01 KWNH 152110
FFGMPD
CAZ000-160130-

Mesoscale Precipitation Discussion 0622
NWS Weather Prediction Center College Park MD
509 PM EDT Mon Jul 15 2024

Areas affected...Peninsular and Eastern Transverse Ranges of
Southern California...

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

Valid 152105Z - 160130Z

SUMMARY...Slow moving thunderstorms with modest moisture/flux
convergence may result in spots of 1-1.5" in 1-2 hours resulting
in possible localized flash flooding.

DISCUSSION...GOES-W Visible imagery shows the first cycling
updrafts along the peaks of the Peninsular Range, eastern San
Bernandino, Little Bernandino and Pinto Ranges.  Very high
moisture resides within the Imperial Valley into the Coachella
Valley with surface Tds in 60s and low 70s from Thermal, CA south
to the Salton Sea.  GPS and RAP analysis suggest total PWATs of
1.25" as far north as DAG, with the average of 1.5" in the lower
valley.   With high theta-E airmass in the valley, CAPEs have
reached 2500 J/kg looking for the upslope ascent forcing.  Winds
have increased recently with 5-10kts of upslope flow from both the
moist/unstable Gulf of California air and from upslope off the
cooler Pacific.  Deeper layer flow though provides the 850-700mb
weak but sufficient convergent ascent before turning slightly
northward along the spine of the ridge.  This should provide
sufficient moisture flux to eventually support .5"-1"/hr rates
after these first few up/downdraft cycles moisten the drier low
level profile.

Steering is weak but eventually bends back toward the NW edge of
the ridge with weak westerly diffluence support from 30-35kt 3H
jet streak off the California Bight.  As such, slow cell motions
may allow for an hour or so of residence in and east of the ridge
lines.  Given barren rock and recent heavy rainfall in similar
locations, enhanced runoff may result in localized flash flooding
conditions over the next few hours before instability fully wanes.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-90-LI0LaVUoEVABRr_nvXL7Xt17irBNbd9DtPitWUFovRLzSfFD2hIO0ao7ReH044si=
vFwyvv60ETFX-lomjY25x-w$  for graphic product...

ATTN...WFO...PSR...SGX...VEF...

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

LAT...LON   35171681 34911608 33801532 33581614 32571577=20
            32451642 33831685 34301729 34911722=20

=3D =3D =3D
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