961
AWUS01 KWNH 161930
FFGMPD
CAZ000-170130-

Mesoscale Precipitation Discussion 0021
NWS Weather Prediction Center College Park MD
228 PM EST Mon Feb 16 2026

Areas affected...Southern California...

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

Valid 161930Z - 170130Z

SUMMARY...Progressive cold front with strong pre-frontal southerly
moisture flux will continue to shift eastward into the eastern
Transverse and Peninsular Ranges through this evening.  Less
orthogonal ascent along terrain will reduce rainfall totals but
intense sub-hourly totals up to 1" that may cause urban flooding
and issues in and downstream of recent burn scars.

DISCUSSION...RADAR and GOES-W visible imagery show a narrow band
of intense showers/weak convective cores exiting Ventura county
into S Los Angeles county extending southward through the eastern
Channel Islands and starting to approach the southward turn of the
coast across Orange and San Diego counties.  Very strong moisture
flux of 40-50kts of 925-850mb flow and steadily increasing
moisture per CIRA LPW nearing .75" in that layer. Veering post
frontal flow continues to be stark, with  directional convergence
remains between 75-90 degrees.  Given the strength over 30kts (up
to 50kts), it will continue to result in strong moisture flux for
the convective elements supporting hourly rates of .75-1".  This
will continue what has been  have observed moving through
southward facing terrain of the Transverse Range including the
Santa Monica Range, where totals of 2-3+" have been observed
resulting in localized flash flooding.

The strength of flow even below 850mb will continue to intersect
the San Gabriel and San Bernardino Ranges lower to mid slopes with
similar rates near .75-1"/hr though highest peaks will start
converting over to moderate/heavy snowfall.  However, with
reducing southerly fetch, the Peninsular Ranges will see a quick
pick up, but with less orthogonal convergence/orographic ascent
will also see diminishing rates and therefore totals between
22-00z tonight.  The lack of moisture flux off the California
Bight will also reduce the effective ascent through the TROWAL
further back west across the central Transverse Ranges where
lighter rain will continue to slowly add to the totals through 00z
as well.  With the loss of orographic ascent/convergence and
deeper moisture availability, rates will reduce but increased
westerly flow and steepening lapse rates aloft before the main
cold front will allow for a few rounds of scattered upslope
showers with .1-.25"/hr rates/totals adding to the initial
mainline.  Still, the overall risk for flash flooding will be
limited to urban and recent burn scars east and South of the LA
Basin.

Gallina

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

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

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

LAT...LON   34701850 34251725 33811664 32841626 32471628
            32451709 32971743 33471782 33621834 33831850
            33981871 34221933 34601910