AWUS01 KWNH 130959
FFGMPD
CAZ000-ORZ000-132158-

Mesoscale Precipitation Discussion 1221
NWS Weather Prediction Center College Park MD
458 AM EST Thu Nov 13 2025

Areas affected...much of central and northern California

Concerning...Heavy rainfall...Flash flooding likely

Valid 130958Z - 132158Z

Summary...Heavier downpours should result in instances of urban
flooding around San Francisco and vicinity during and after
morning commute. Heavier rainfall will also spread into more of
northern and central California from 13Z/6a PT through the
evening. Flash flooding is expected especially near burn scars,
urban areas, and other terrain-favored spots.

Discussion...As of 0955Z, a band of convection was beginning to
organize along a front extending from near 80 miles southwest of
Eureka to 180 miles southwest of Monterrey. Individual convection
along this band was streaming northward at a decent clip.
However, the band was only moving slowly eastward and already
favoring areas of repeating over open waters. 500 J/kg MUCAPE and
areas of 1.3+ PW values were supporting the convective band, and
MRMS data was already estimating 0.5-0.7 inch hourly rain rates
over land just southwest of Eureka.

The convective band and associated mid-level system are expected
to make only slow eastward progress toward more land areas of
California today. As the systems approach, low-level wind fields
will strengthen, colliding with terrain and locally enhancing rain
rates in many areas. Rates could reach 1 inch/hr on a localized
basis. These rates will overspread portions of the San Francisco
Metro beginning in the 12Z/5a PT hour and persist through the
afternoon, impacting morning rush with wet roads and areas of
excessive runoff. Portions of north-central through east-central
California will also experience terrain-enhanced heavy rainfall,
with some of the heavier rates (exceeding 0.75 inch/hr) falling on
sensitive ground conditions and burn scars. Flash flooding is
expected on at least an isolated basis. These areas could include
terrain near/north of Redding (beginning around 13Z/6a PT) and
upslope areas of the Sierra (near/east of Chico) beginning around
14Z/7a PT. Heavy rainfall could last for 8-12 hours in many of
the aforementioned areas, with totals of 3-5 inches likely through
00Z Fri Nov 14.

Again, at least a few instances of flash flooding are expected
given the scenario.

Cook

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

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

LAT...LON 42252315 42102191 41712116 41262098 40792092
40142070 38461980 37801954 36581993 35282051
35472124 37712319 40152469 41802483 42162420

$$
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