583
AWUS01 KWNH 221702
FFGMPD
TXZ000-OKZ000-222200-

Mesoscale Precipitation Discussion 1042
NWS Weather Prediction Center College Park MD
101 PM EDT Sun Sep 22 2024

Areas affected...Southwest to Central East OK...Southeast TX
Panhandle...

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

Valid 221700Z - 222200Z

SUMMARY...Slow moving, back-building cells with rates of 1"/hr may
pose localized 1-1.5" totals and possible flash flooding
conditions.

DISCUSSION...GOES-W and Regional RADAR mosaic have started to
depict increasing convective activity in both coverage and
vertical depth with peak heating of the day.  The highly
anomalous, over 3.5 standard anomaly units from climatology, core
of the closed low is bottoming out across SW California with
vorticity center at the southern base; this is allowing for an
elongation/stretching of the mid-level deformation zone to extend
across SW to NE San Bernadino county with increased deep layer
convergence.  Given steepening lapse rates with cold air advection
aloft, surface heating into the 80s is starting to support surface
based CAPE values from 500-1000 J/kg to develop over the Southern
California Deserts toward the Colorado River Valley near S Nevada.
 While deep layer moisture is a bit limited with only Tds in the
upper 40s, low 50s and total PWat values in the .75 to 1" range.
The convergence within the band and orographic ascent confluent
across the San Bernadino/Little Bernadino/San Jacinto Ranges
supports stronger vertical development and sufficient moisture
flux to support .5-1"/hr rates.

Limited cell motions given proximity to the closed low/deformation
zone will allow for very slow/stationary motion with upstream
redevelopment/backbuilding along the deformation band across NE
CA.  Propagation may also allow cells along the mountain ridges
into the Cochella Valley with time.  This may allow for spotty
.75-1" totals with an isolated 1.5" total remains possible.  Given
naturally low FFG values less than these hourly rates and
potential; an isolated flash flooding incident or two is
considered possible across the area through the late
afternoon/evening hours.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...AMA...LUB...OUN...TSA...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON   36109607 36069525 35799487 35339499 34969571
            34729672 34459805 34099985 33890132 34520180
            35150101 35629991 35919906 36089804 36069700