River Flood Warning 11, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1011 PM PST Thu Mar 9 2023

.SYNOPSIS...An atmospheric river will continue to impact the
entire San Francisco Bay Area and Central Coast overnight into
Friday. The main impacts will be strong winds and widespread
rainfall resulting in flooding concerns. Lingering, yet lighter
precipitation will continue into the weekend with yet another
atmospheric river arriving early next week.

&&

.DISCUSSION...as of 9:28 PM PST Thursday...Forecast remains on
track with atmospheric river bringing copious rainfall to the
hills and strong winds to most locations throughout the Bay Area.

Massive moisture transport is underway as the long watched plume
of moisture has worked its way across the Pacific and now
spreading onshore across the Bay Area and Central Coast. It took a
bit to scour the cool air out with highs today generally in the
upper 40s and lower 50s. In fact many locations now warmer than
they were this afternoon. Here in Monterey we've reached 62
degrees with southerly downslope flow off the Santa Lucia range.
Gusty southerly winds continue across the region with widespread
gusts from 40-50 mph leading to reports of downed trees and limbs
along with associated power outages. Gale Warnings are in effect
over the ocean waters and we are seeing gusts in excess of 40
knots for the nearshore buoys, quite impressive.

So far the most widespread flooding has been reported in the North
Bay, mainly across the lower elevations of Sonoma county where
many of the creeks showed rapid rises late this afternoon and
evening. Urban and small stream flood advisories are in effect
around Santa Rosa. Be extra careful overnight and dont drive
across flooded roadways. Given the saturated soils there is
nowhere for the water to go and we are seeing very rapid rises on
area creeks. We will be watching the Napa river as well overnight
with the latest forecasts now bringing the river to monitor stage
at both St Helena and Napa early Friday morning.

Meanwhile down in the Santa Cruz mountains the rain buckets are
starting heading into overdrive with Ben Lomond over 1/2 inch per
hour and storm totals quickly approaching 2 inches. This is an
ominous signal for a forecast rise on the San Lorenzo river into
Flood Stage on Friday. Please listen to evacuation orders from
officials. In addition to the San Lorenzo we are expecting
flooding impacts on the Salinas, Pajaro and Carmel rivers starting
tomorrow and lasting into the weekend.

In the last hour we've seen some lightning strikes across
interior Contra Costa county and some t-storms are now organizing
as they move into the Central Valley.

Looking ahead, expect periods of rain and wind to continue
overnight (Wind advisory remains in effect into Friday). Strongest
rain in the hills. The next pulse of energy looks to arrive around
sunrise with renewed heavy rain region wide for the Friday morning
commute. Area of concern for heaviest rain will shift southward
into the Santa Cruz and Santa Lucia range late tonight into
Friday. WPC has put coastal Monterey into high risk category for
excessive rainfall. Some of the mesoscale models are putting out
some obscene rainfall totals in the Big Sur hills the next 12-18
hours. This water will drain into the Carmel River and thus lead
to flood concerns there as well as the Big Sur river.

Precip will wind down for the North Bay and Peninsula Friday
afternoon/evening but linger for the Central Coast. The AR shifts
south of the area late Friday night.

Saturday and Sunday light rain showers continue but no widespread
heavy rain forecast this weekend.

Will then be watching yet another atmospheric river arriving
around Tuesday. Early qpf forecasts show another 4 inches or so
for the usual wet spots in the Sonoma hills and Santa Cruz mtns.

&&

.AVIATION...as of 10:00 PM PST Thursday...For the 06Z TAFs.
Plentiful moisture advecting into the region, as rain intensity is
increasing over the SF Bay area into northern Monterey Bay.
Flight rules vary from VFR to LIFR with low vsby in RA/BR and
varying cig levels. S/SE winds are gusting 25-45 kt, with only
North Bay terminals sheltered from the stronger winds. Stronger
gusts are observed in hills above 1000 ft due to a strong
southerly low- level jet, reaching 50-60 kt. Thus, seeing reports
of LLWS and turbulence across the area. Models indicate strongest
winds and heaviest rain will arrive overnight, then diminish from
north to south beginning around sunrise through the afternoon,
with moisture becoming more focused over the Central Coast.
Chances for thunderstorms will also be monitored overnight and
Friday morning, as a few lightning flashes are currently detected
about 600 miles off the CA coast.

Cigs will be slow to clear Friday afternoon, with best chances
north of SF Bay. Otherwise, MVFR cigs persist with lighter winds
veering to the W/NW.

Vicinity of KSFO...Prevailing IFR/MVFR at area terminals with
light to moderate rain. Winds strong and gusty out of the south
with gusts 30-40kt, occasionally up to 45 kt, then diminishing
through the morning. LLWS and turbulence continuing through early
morning as well with strong southerly LLJ. MVFR/IFR conditions
overnight through the morning in RA/+RA and low cigs. Winds veer
to the SW/W later in the morning, but timing still uncertain. MVFR
Friday with possible VFR by late afternoon or early evening.

KSFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Intermittent rain with varied
VFR/MVFR/IFR conditions at area terminals. Bands of heavier rain
arrive after midnight and last through the morning, with IFR/MVFR
conditions. Gusty SE/S winds peaking overnight, 35-45 kt, perhaps
up to 50 kt along the coast. LLWS reported at KMRY, which may
continue overnight, until LLJ weakens by early morning. Showers
may linger through the afternoon, with IFR/MVFR conditions
expected, as cigs will be slow to lift. Winds will weaken and turn
more onshore. Low cigs continue tonight.

&&

.MARINE...as of 08:34 PM PST Thursday...Strong southerly winds up
to gale force diminishing from north to south overnight through
Friday morning, as a strong storm pushes southward. Also,
potential for occasional gusts reaching low end storm force
speeds. In addition, widespread heavy rainfall with slight chances
of thunderstorms late tonight into Friday, along with steep,
hazardous seas are expected. Southwesterly swell will arrive and
build over the waters this weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...Flood Watch...CAZ006-502>506-508>510-512>518-528>530
             Wind Advisory...CAZ006-502>506-508>510-512>518-528>530
             GLW...SF Bay
             GLW...Mry Bay
             GLW...Pigeon Pt to Pt Pinos 0-10 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Arena to Pt Reyes 0-10 nm until 3 AM
             GLW...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
             GLW...Pt Arena to Pigeon Pt 10-60 nm until 3 AM

&&

PUBLIC FORECAST: RW
AVIATION: Lorber
MARINE: Lorber

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1036 PM PST THU MAR 9 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1016 PM     NON-TSTM WND DMG 7 NNW HEALDSBURG        38.71N 122.91W
03/09/2023                   SONOMA             CA   LAW ENFORCEMENT

            LARGE OAK TREE AND POWER LINES DOWN BLOCKING
            ALL LANES.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1042 PM PST THU MAR 9 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1029 PM     HEAVY RAIN       2 ESE CALISTOGA         38.58N 122.55W
03/09/2023  E0.63 INCH       NAPA               CA   LAW ENFORCEMENT

            MUD SLIDE MOVING DEBRIS OVER SILVERADO TRL.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1045 PM PST THU MAR 9 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1029 PM     HEAVY RAIN       2 W MONTE RIO           38.47N 123.04W
03/09/2023  E2.00 INCH       SONOMA             CA   LAW ENFORCEMENT

            MUD SLIDE MOVING DEBRIS OVER HWY 116.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1055 PM PST THU MAR 9 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0927 PM     NON-TSTM WND GST 1 S SAUSALITO           37.85N 122.49W
03/09/2023  M65 MPH          MARIN              CA   TRAINED SPOTTER

            TRAINED WEATHER SPOTTER REPORTED A WIND GUST
            OF 65 MPH.

&&

EFL

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