541
AWUS01 KWNH 132317
FFGMPD
CAZ000-140515-

Mesoscale Precipitation Discussion 1194
NWS Weather Prediction Center College Park MD
716 PM EDT Mon Oct 13 2025

Areas affected...Central CA Coastal Ranges into the Central Valley

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

Valid 132315Z - 140515Z

SUMMARY...Heavy showers and potentially a few thunderstorms will
impact areas around the Bay Area through early this evening. While
spreading gradually farther south along the coastal ranges, some
of these heavier rains should spread into portions of the Central
Valley. An urban flooding threat will exist, and especially around
the Bay Area, with an isolated burn scar flash flood threat as
well over some of the adjacent higher terrain.

DISCUSSION...The latest GOES-W WV suite shows a strong upper-level
low continuing to deepen as it drops southward just offshore of
the West Coast. A rather strong frontal structure associated with
these height falls coupled with enhanced upper-level jet
divergence/forcing overspreading the central CA coastal ranges,
including the Bay Area, along with adjacent portions of the
Central Valley will support areas of heavy showers and potentially
a few stronger thunderstorms going through the evening hours.

A nose of MUCAPE values reaching 250 to 500 J/kg is noted along
and just ahead of a developing frontal occlusion near the Bay
Area, and radar imagery has been showing an increase in linear
bands of convection along and just ahead of the front as it pivots
inland from the coast. Deep layer forcing is expected to
strengthen this evening which coupled with moist Pacific flow
should favor some linearly oriented bands of convection to
potentially make it even into parts of the Central Valley.

Lowering ELs associated with the upper low and modest instability
will favor low/warm-topped convective elements in this dynamically
forced environment that will be rather efficient and capable of
producing rainfall rates of up to 1 inch/hour.

The relatively high rainfall rates coupled with favorable upslope
flow into the coastal ranges will support some spotty 2 to 3+ inch
rainfall totals. Generally, the interior areas of the Central
Valley will see lesser totals, but some of the stronger convective
elements here that occur may foster some locally excessive totals
of 1 to 2+ inches.

Concerns will exist for some urban flooding, and especially around
the Bay Area through early this evening. Some of the area burn
scars will also need to be closely watched for at least an
isolated concern for flash flooding and debris flow activity.

Orrison

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

ATTN...WFO...EKA...HNX...LOX...MTR...STO...

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

LAT...LON   40672288 40552224 39362123 38122061 36672049
            35892024 35372018 35252070 35542130 36122186
            36792231 37442256 38762273 40092333