Strong Wind in California, December 11, 2022

Area Forecast Discussion
National Weather Service San Francisco Bay Area
140 AM PST Sun Dec 11 2022

.SYNOPSIS...Scattered showers and isolated storms will continue
into tonight. Cooler temperatures through midweek with frost and
valley freezes possible. Rain chances may return late week towards
the weekend.

&&

...Scattered Showers and Isolated Thunderstorms Possible Today...

.DISCUSSION...as of 01:35 AM PST Sunday...

Today and Tonight:

A cold core upper low -- now centered offshore from the Redwood
Coast -- will advance towards the Bay Area by this evening. The
upper system will escort a gradually filling surface low pressure
area as it drops south along the coastline this afternoon. Given
steep lapse rates and very cold temperatures aloft look for
scattered instability showers to persist through today and into the
overnight hours. Given appreciable most unstable CAPE (on the order
of 200+ J/kg along the coast and low freezing levels would expect
isolated thunderstorm development as well with lightning and small
hail being the primary hazards. This solution is well depicted in
simulated reflectivity fields from the convection allowing models
which show a smattering of transient higher reflectivity cores
throughout the day and into the evening. While additional rain
amounts won't be nearly as impressive as the prior 24 hour totals,
still expect locally heavy amounts with totals through tonight
averaging over 0.25 inches, with locally higher 1-2 inch liquid
equivalents for the Santa Lucias. Given antecedent conditions will
need to keep an eye on the potential for briefly higher rain rates
over the Colorado/Dolan/River wildfire burn scars in Monterey County
but overall guidance suggests the potential for reaching debris flow
thresholds is quite low. Minor street flooding issues may also
persist for areas with repeated bouts of heavier rainfall. As
noted previously snow levels are already dropping early this
morning to around 3,700 feet in the North Bay and around 4,300
feet at Point Sur. The arriving moisture today should coincide
with these lowering levels to produce snowfall in the region's
higher peaks. So for the Santa Lucias the most likely amounts are
around 2-4 inches with 6-8 inches possible in the higher
elevations. However a reasonable worst case scenario could produce
over 8 inches locally if things line up just right moisture and
temperature-wise. Otherwise expect a cool and somewhat blustery
day with low elevation temperatures generally in the lower to mid
50s. Mountain readings will generally top out in the 40s except
lower 30s on the higher peaks of the Santa Lucias. As skies clear
tonight expect temperatures to drop into the 30s except lower 40s
along the coast and bays. Near-freezing temperatures are possible
for the inland valleys of the North Bay.

Monday through Wednesday:

A shortwave ridge will take hold through Tuesday as a closed upper
circulation pinwheels over the northeast Pacific. This will support
high pressure during the first portion of the period with some
weakening expected towards midweek. There is low confidence (less
than 30 percent) for light rain developing on Wednesday in
association with a weak perturbation passing through the region.
Some ensemble members and consensus models depict light
accumulations during this time however rain is largely absent among
the deterministic model runs and other ensemble members. Kept
collaborated slight chance PoPs in the forecast for the moment until
things become clearer. Otherwise this will be a colder period with
Monday and Tuesday morning being of particular concern. Lows each
morning should be in the 30-35 degree range for most inland
locations with some upper 20s in the coldest valleys. Closer to the
coast expect lows of around 38-42 degrees. Unsheltered or marginally
sheltered populations will be at risk due to the very cold
temperatures during this time. There is less confidence in
temperatures for Wednesday night given an increase in cloud cover
along with the possible arrival of precipitation. Highs each day
will be in the lower to mid 50s for the lower elevations, with 30s
and 40s in the mountains.

Thursday through Saturday:

Deterministic models and their ensembles are in good general
agreement early in the period with a closed low pressure area over
the eastern Pacific and mostly dry conditions. However spread
increases in the envelope of solutions for late week into the
weekend. This hinges on differences in how the large-scale features
are handled including how close/when the upper low approaches the
west coast. As such ensemble solutions are in poor agreement on the
arrival time and amounts for any potential rainfall. This is
reflected in the output from the National Blend of Models which
depicts an elongated period of slight chance to change PoPs across
the area over the weekend. So while we expect a more unsettled
pattern during this time confidence remains low with respect toe the
details and whether/when additional rainfall will impact the region.
Stay tuned for details. Otherwise look for a continuation of
seasonally cool temperatures with low elevation highs in the 50s and
lows mostly in the 30s to lower 40s.

&&

.AVIATION...As of 9:54 PM Saturday...For the 06Z TAFs. IFR-MVFR
with scattered moderate to heavy showers and a slight chance of
thunderstorms. An amplifying, cold 500 mb low (500 mb temp near
-32 Celsius) will move in from the northwest tonight and Sunday
morning. Another spoke of energy within the 500 mb low will move
across the Bay Area and north Central Coast Sunday evening and
night with moderate to heavy showers redeveloping.

Vicinity of SFO...Showers continuing, occasionally moderate to heavy
with MVFR tonight and Sunday morning. VFR with a few showers late
Sunday morning and afternoon, MVFR with moderate to heavy showers
redeveloping Sunday evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR-MVFR with moderate to heavy showers
tonight through Sunday evening, showers continuing into early
Monday morning.

&&

.MARINE...as of 9:35 PM PST Saturday...A cold, deep low pressure
system arriving from the northwest will result in moderate to
heavy showers and a slight chance of thunderstorms through the
remainder of the weekend. Gusty west winds and fresh, steep wind
waves continuing into early week. Another low pressure system will
approach the offshore waters from mid to late next week, bringing
a chance of rain late next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...SF Bay from 3 PM
             SCA...Mry Bay
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm

&&

PUBLIC FORECAST: SPM
AVIATION: Canepa
MARINE: Canepa

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
942 PM PST SAT DEC 10 2022

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

0804 PM     FLOOD            29 SW KING CITY         35.89N 121.46W
12/10/2022                   MONTEREY           CA   LAW ENFORCEMENT

            LARGE ROCKS IN BOTH NB/SB LANES OF HW1 NEAR
            WILLOW CREEK PER CHP.

&&

SPM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
246 AM PST SUN DEC 11 2022

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

1037 PM     HEAVY RAIN       2 WNW BOULDER CREEK     37.15N 122.17W
12/10/2022  E0.30 INCH       SANTA CRUZ         CA   LAW ENFORCEMENT

            LARGE BOULDER IN THE ROAD AT 16587 JAMISON
            CREEK RD.

1239 AM     HEAVY RAIN       1 SE MONTEREY           36.59N 121.87W
12/11/2022  E0.30 INCH       MONTEREY           CA   LAW ENFORCEMENT

            FLOODING ON THE OFFRAMP OF SR1-N AT FREMONT
            ST.

1231 AM     HEAVY RAIN       1 WSW DANVILLE          37.81N 121.99W
12/11/2022  E0.40 INCH       CONTRA COSTA       CA   LAW ENFORCEMENT

            OFFRAMP ON 680N AT SYCAMORE VALLEY RD IS
            COMPLETELY FLOODED.

1251 AM     HEAVY RAIN       2 ENE ORINDA            37.89N 122.15W
12/11/2022  E0.50 INCH       CONTRA COSTA       CA   LAW ENFORCEMENT

            ROADWAY FLOODING ON SR-24W JUST EAST OF
            ACALANES RD.

0959 PM     NON-TSTM WND GST 2 SW MORAGA TOWN        37.82N 122.15W
12/10/2022  E30 MPH          CONTRA COSTA       CA   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROADWAY ON PINEHURST RD
            BETWEEN SKYLINE RD AND CANYON RD.

0359 PM     FLOOD            1 N LOS GATOS           37.25N 121.96W
12/10/2022                   SANTA CLARA        CA   LAW ENFORCEMENT

            LARK AVE ON-RAMP TO SB-17 COMPLETELY
            FLOODED.

0828 PM     FLOOD            8 N HOLLISTER           36.97N 121.42W
12/10/2022                   SANTA CLARA        CA   LAW ENFORCEMENT

            SR-152 AT SAN FELIPE RD IS FLOODED.

0943 PM     FLOOD            2 W PIEDMONT            37.83N 122.27W
12/10/2022                   ALAMEDA            CA   LAW ENFORCEMENT

            STANDING WATER IN TWO LANES AT 3601
            TELEGRAPH AVE IN OAKLAND.

0120 AM     NON-TSTM WND DMG DEL MONTE FOREST        36.59N 121.95W
12/11/2022                   MONTEREY           CA   LAW ENFORCEMENT

            TREE FELL DOWN ON POWER LINES. POWER POLE
            ALSO FELL DOWN.

0128 AM     NON-TSTM WND DMG 3 NNE SCOTTS VALLEY     37.10N 121.98W
12/11/2022                   SANTA CRUZ         CA   LAW ENFORCEMENT

            WIRES AND TREES DOWN ON BOTH SIDES OF ROAD
            AT 533 GLENWOOD CUTOFF.

0135 AM     NON-TSTM WND DMG 1 WNW FELTON            37.05N 122.09W
12/11/2022                   SANTA CRUZ         CA   LAW ENFORCEMENT

            TREE FELL ONTO ROAD BLOCKING BOTH LANES ON
            FELTON EMPIRE RD, JUST NORTH OF KRAZY ACRES
            LN.

0139 AM     NON-TSTM WND DMG 2 N ELKHORN             36.84N 121.72W
12/11/2022                   MONTEREY           CA   LAW ENFORCEMENT

            TREE DOWN ACROSS HALF OF THE ROAD AT 265
            HIDDEN VALLEY RD.

&&