Severe Thunderstorm Warning 14, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco CA
126 PM PDT Wed Mar 12 2025

...New SYNOPSIS, SHORT TERM, LONG TERM...

.SYNOPSIS...
Issued at 125 PM PDT Wed Mar 12 2025

An active weather pattern continue today with periods of rain,
strong wind, thunderstorm chances, and some snow to the higher
regional mountains. While the bulk of the impacts arrive today
through Thursday, unsettled weather will continue into early next
week.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 125 PM PDT Wed Mar 12 2025

Things remain generally on track as the main frontal band is
offshore and will move into the North Bay early this afternoon, Bay
Area midday, and Central Coast later this afternoon and evening. It
is along the main band when we can see up to 0.50" per hour rainfall
rates. There are indications of a Narrow Cold-Frontal Rainband
(NCFR) showing up offshore, so that will need to be closely
monitored as it moves inland. This is when we are expected to see
minor urban and small stream flooding and when we are expecting to
see the strongest winds with gusts up to 55 mph, up 70 mph in the
higher terrain and typically windier spots.

In wake of the frontal passage, conditions will become more
convective in nature as the colder air mass sets in across the
region. Scattered showers and the potential for isolated
thunderstorm will persist into the night and early Thursday morning.
When all said and done with this first system, coastal areas will
see 1.00-1.50", with 2.00-4.00" in the Santa Cruz mountains and the
Santa Lucia Range. Inland valleys will see anywhere from 0.5-1.00",
with 1.00-2.00" in the inland mountains and North Bay mountains.

In addition, snow will be likely across the higher elevations as
snow levels drop to between 2,200 to 3,000 feet across the North Bay
and down to about 3,000 feet across the Central Coast overnight. The
highest peaks in the Santa Lucia range can expect up to 12 inches of
snowfall with light accumulations around Mt. Hamilton. Rain/show
showers and/or thunderstorms will taper off across the region by
midday Thursday.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 125 PM PDT Wed Mar 12 2025

Rain will return Thursday night into Friday morning as another
trough axis pushes inland across the region. From this system we are
expecting an additional 0.25-0.50" in most areas with up to 1.25" in
the higher coastal terrain. Saturday continues to look mostly dry,
other than light rain over the North Bay.

Yet another system arrives on Sunday over the North Bay and will
clear the Central Coast by Monday afternoon. Again, providing
similar rainfall as the aforementioned system. There is some
uncertainty beyond the middle of next week, yet the pattern will
likely remain active.

&&

.AVIATION...
(18Z TAFS)
Issued at 1156 AM PDT Wed Mar 12 2025

A cold front is building into the region. Prefrontal showers and
breezy south to southeast winds have spread across the region with
some spotty MVFR CIGS. The front will move in from the northwest and
spread southwest through the afternoon. This means STS will be the
first to see the more moderate to at times heavier rainfall to
arriving along the main rain band, which afternoon for areas to the
south. In addition to the increased rain rates, strong and gusty
southerly winds will flow along the main rain band. Winds reduce but
remain breezy to gusty behind the front with scattered shower
activity through the night. Spotty thunderstorm chances will be
possible overnight and into Thursday. The main area of Thunderstorm
risk will be over the marine environment, with only slight chances
overland. Winds shift and become more westerly and northwesterly
into early Thursday, with shower and storm chances exiting that
afternoon.

Vicinity of SFO...MVFR CIGS and spotty showers are building into the
SF BAY. Expect increased rain rates along with stronger and gustier
winds as the main rain band arrives in the mid to late afternoon
afternoon. Winds turn slightly more southwest in the wake of the
main band, but remain strong, however rain rates will reduce. Expect
scattered showers through the night with slight chances for isolated
thunderstorms. Winds turn more westerly in the late night. Shower
and storm chances to exit by the end of the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Spotty pre-frontal showers are moving
through the area along with building mid-level clouds. Breezy
southerly winds become stronger and gustier as the main rain band
arrive in the mid to late afternoon. Rain rates will be moderate
to, at times, heavy, leading to reduced visibility. Behind the
front, winds turn southwest, with lingering shower activity expected
through the night. Chances for isolated storms increase overnight
off the coast and around the Monterey Bay with around a 20% chance
at the terminals early Thursday. Expect winds to turn northwest mid-
thursday morning with rain and storm chances exiting slightly beyond
the TAF period.

&&

.MARINE...
(Today through Monday)
Issued at 1156 AM PDT Wed Mar 12 2025

Widespread Gale warnings are in effect through the day. Rough
seas will build through the day. Overnight, there is a 30 percent
chance for thunderstorms and associated strong gusts. Seas will
remain rough into next week as a series of storms moves through.

&&

.BEACHES...
Issued at 1156 AM PDT Wed Mar 12 2025

Hazardous beach conditions are expected Wednesday and Thursday
as moderate period westerly swell builds to support breaking
waves up to 15 feet. Additional hazardous surf will be possible
again this Sunday. As always, please remember to stay off of
rocks and jetties, keep pets on a leash, and never turn your back
on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 8 PM PDT this evening for CAZ006-502>506-
     508>510-512>518-528>530.

PZ...Gale Warning until 9 PM PDT this evening for Mry Bay-Pigeon Pt
     to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena
     to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-
     SF Bay N of Bay Bridge.

     Gale Warning until 3 AM PDT Thursday for Pt Arena to Pt Reyes 0-
     10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Murdock
MARINE...Murdock

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Special Weather Statement
National Weather Service San Francisco CA
224 PM PDT Wed Mar 12 2025

CAZ508-509-512-513-122200-
Santa Clara Valley Including San Jose CA-San Francisco Bay
Shoreline CA-Santa Cruz Mountains CA-San Francisco Peninsula
Coast CA-
224 PM PDT Wed Mar 12 2025

...A LINE OF STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN SANTA
CRUZ...SAN MATEO...NORTHWESTERN SANTA CLARA AND SOUTHWESTERN ALAMEDA
COUNTIES UNTIL 3 PM PDT...

At 224 PM PDT, Doppler radar was tracking a line of strong
thunderstorms extending from over El Granada to 21 miles west of
Boulder Creek, or extending from 6 miles southwest of Millbrae to 27
miles west of Santa Cruz, moving northeast at 45 mph.

HAZARD...Wind gusts of 50 to 55 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is possible.

Locations impacted include...
  San Jose, Fremont, Sunnyvale, Santa Clara, San Mateo, Redwood
  City, Mountain View, Palo Alto, Cupertino, Menlo Park, Foster
  City, Los Altos, Burlingame, San Carlos, East Palo Alto, Belmont,
  Half Moon Bay, Hillsborough, Los Altos Hills and Atherton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

Torrential rainfall is also occurring with these storms and may lead
to flash flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3759 12235 3759 12234 3758 12236 3753 12228
      3757 12229 3756 12225 3753 12227 3755 12222
      3752 12225 3749 12222 3749 12223 3746 12210
      3748 12208 3746 12205 3746 12193 3711 12233
      3720 12241 3736 12240 3748 12245 3750 12250
TIME...MOT...LOC 2124Z 217DEG 39KT 3753 12246 3728 12246 3710 12250

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 TO 55 MPH

Behringer

Special Weather Statement
National Weather Service San Francisco CA
254 PM PDT Wed Mar 12 2025

CAZ508-510-515-122215-
San Francisco Bay Shoreline CA-East Bay Interior Valleys CA-East
Bay Hills CA-
254 PM PDT Wed Mar 12 2025

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL CONTRA COSTA AND
NORTHWESTERN ALAMEDA COUNTIES UNTIL 315 PM PDT...

At 254 PM PDT, Trained spotters reported a strong thunderstorm over
Orinda, or near Berkeley, moving northeast at 50 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Trained spotters reported.

IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is possible.

Locations impacted include...
  Oakland, Concord, Berkeley, Richmond, San Leandro, Mountain View,
  Alameda, Walnut Creek, Pittsburg, Danville, Martinez, Pleasant
  Hill, Lafayette, El Cerrito, Castro Valley, Hercules, Albany,
  Pinole, Orinda and Moraga.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

&&

LAT...LON 3787 12232 3789 12231 3791 12233 3805 12219
      3802 12215 3805 12199 3796 12187 3768 12217
      3771 12220 3771 12219 3774 12226 3775 12225
      3773 12221 3775 12221 3776 12222 3776 12221
      3777 12229
TIME...MOT...LOC 2154Z 218DEG 44KT 3786 12219

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

Behringer

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