199
AWUS01 KWNH 172145
FFGMPD
CAZ000-180345-

Mesoscale Precipitation Discussion 1229
NWS Weather Prediction Center College Park MD
445 PM EST Mon Nov 17 2025

Areas affected...Southern California...

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

Valid 172145Z - 180345Z

SUMMARY...Heavy rainfall conditions improving, but still an
isolated potential for .5"/hr rates with max totals in the
Transverse Ranges near 1.5" through evening. Saturated grounds and
urban locations have possibility for isolated flooding concerns.

DISCUSSION...GOES-W Visible and Regional RADAR mosaic denotes a
broader shield of mid-level strato-cu across the western portions
of the Transverse Ranges across E Santa Barbara county indicative
of a subtle southwesterly shortwave lifting northeastward through
in proximity to the cold front.  This is in some response to the
larger scale digging closed low orienting more NW to SE providing
deeper layer divergence above 500mb and overall DPVA through the
California Bight into Southern California this afternoon into
evening.   However, the lower level pressure gradient is
broadening through the Bight and winds have diminished throughout
the afternoon.  Still, 20-25kts of southerly flow coincident with
the vertically stacked moisture plume still advects .75 to 1"
total PWats (IVT values of 250-300 kg/m/s) fairly orthogonal to
the Transverse Ranges of Ventura and Los Angeles counties and will
spill over to the San Bernardino Ranges through evening.
Localized totals of 1-1.5" are possible in the highest elevations
but overall rates and ascent will be diminishing with the
weakening wind field.

Off the terrain,  the environmental conditions are very limited
for flooding, but recent saturated grounds per NASA SPoRT suggest,
above average run-off could be expected.  With that stated, some
modest surface to boundary layer heating has developed this
afternoon providing some weak but sufficient instability;  MLCAPEs
of 150-250 J/kg are present and with 10-12 kg/m/s deep layer
moisture convergence along the front, some vertical development
and enhanced rainfall rates are possible through the evening
likely topping out around .5"/hr perhaps inducing some isolated to
widely scattered incident(s) of urban flooding concerns through
03z.

Gallina

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

ATTN...WFO...HNX...LOX...SGX...

ATTN...RFC...RSA...NWC...

LAT...LON   35061949 34961850 34191722 32761696 32611733
            33011763 33531807 33761859 33831901 34401968
            34741979