679
FXUS66 KMTR 111634
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
934 AM PDT Tue Mar 11 2025

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 357 AM PDT Tue Mar 11 2025

An active period of weather sets in later tonight and persists
through the extended forecast. Periods of heavy rain Wednesday into
Thursday morning can be expected with gusty winds up to 50 MPH at
times along the coast, thunderstorms, potentially high surf and
accumulating snow across the highest elevations of the Santa Lucia
coastal range. Numerous rounds of light to moderate rain will move
across our Friday through the weekend and into the beginning of next
week.

&&

.UPDATE...
Issued at 933 AM PDT Tue Mar 11 2025

Weak echos showing up on KMUX Radar over our far southern coastal
waters this morning. This is from a low pressure system approaching
the southern California coast that will move inland later today.
Otherwise, today will be mostly dry with rain returning tonight
across the North Bay and then over the entire region on Wednesday.
No updates needed to the near term forecast at this time.

RGass

&&

.SHORT TERM...
(Today and tonight)
Issued at 357 AM PDT Tue Mar 11 2025

After one more day of pleasant weather today, the forecast for the
first round of rainfall remains on track. Scattered light rain will
begin to move onshore over the North Bay as early as late this
afternoon and gradually increase in coverage and intensity through
the overnight into Wednesday. By sunrise tomorrow more intense
rainfall rates out ahead of the surface front will be ongoing over
portions of the North Bay. By mid-morning, the more intense rainfall
will begin to impact the Bay Area and East Bay, as the surface cold
front approaches the coast. Convergence along the cold front and
surging southerly winds just out ahead of the cold front will
produce wind gusts up to 50mph along the coast with periods of heavy
rain over the Bay Area likely from late morning through early
afternoon, eventually moving farther inland for the remainder of the
afternoon and early evening. Max wind gusts farther inland will be
in the 30-40mph range as the cold front pushes through with rainfall
rates up to 0.5"/hr. Urban flooding and small landslides in the
coastal ranges are possible where rainfall rates are highest.
Rainfall totals for the North Bay south into the coastal ranges of
Marin, Santa Cruz and Monterey County will approach 2" during the
day tomorrow, with lesser amounts inland, including some rain
shadowing into the South Bay.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 357 AM PDT Tue Mar 11 2025

Cooler air aloft associated with the center of the trough will
eventually lead to increased lapse rates and more unstable airmass
with a 10-15% chance for strong thunderstorms developing by
Wednesday evening in the post frontal airmass. However, the surface
trough loses some strength as it approaches land tomorrow evening
with weak short wave ridging aloft at the base of the trough. Strong
wind gusts up to 40mph and small hail are the primary concerns with
any updrafts able to remain organized enough to produce isolated
thunderstorms. Any thunderstorms that do develop should be
shortlived into the early hours of Thursday morning. Although rain
chances persist over much of the area through the day Thursday, it
will not be as widespread or intense as Wednesday. Expect mostly
light scattered rain chances gradually shifting south through the
day. The next round of rainfall begins to move onshore over the
North Bay late Thursday night into early Friday morning, a weak and
progressive trough axis embedded in a wide swath of northwest flow up
to 70kts at times shifts east across much of California during the
day Friday. Once again, scattered light rain chances linger into
Saturday, but most of the area will see little to no rain on
Saturday, with lingering cloud cover helping to keep temperatures 5-
10 degrees cooler than normal. Consensus for Sunday is lacking, with
the NBM possibly lagging behind most current NWP guidance, and may
trend drier over the next couple of updates, with potentially little
to no rain on Sunday. Furthermore, the upper level trough expected
for the beginning of next week has taken on a more positive tilt,
which would be drier and more progressive. Keep checking for updates
for the weekend and beyond as the forecast may change significantly
over the coming days.

&&

.AVIATION...
(12Z TAFS)
Issued at 420 AM PDT Tue Mar 11 2025

Currently VFR at all terminals. VFR through the day with MVFR
ceilings expected at most terminals tonight. A strong cold front
will move through the region from northwest (morning) to southeast
(afternoon) tomorrow. While most impacts will be felt into the
next TAF cycle, winds will become southerly, strong, and gusty and
virga will likely be seen towards the end of the 24-hour TAF
period and into the 30-hour TAF period.

Vicinity of SFO...Currently VFR with northwesterly flow. Winds will
prevail out of the west by this afternoon, slowly transitioning to
become southerly this evening ahead of the cold front becoming
strong and gusty overnight. Rain likely won`t impact the terminal
until the next TAF cycle, but virga will likely be seen in the area
towards the end of the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR and calm at both terminals.
Winds will be diurnal through the TAF period. MVFR ceilings will
return this evening.

&&

.MARINE...
Issued at 933 AM PDT Tue Mar 11 2025

Expect light to moderate seas and winds for today. Southerly
winds will increase late Tuesday night into Wednesday as a strong
cold front approaches from the northwest with gale force gusts
expected as it passes. Scattered thunderstorms are possible
Wednesday afternoon into Thursday which would pose the risk for
locally heavy rainfall and gusty winds, lightning, and pea sized
hail. Seas will be rough to very rough Wednesday through the
weekend.

&&

.BEACHES...
Issued at 420 AM PDT Tue Mar 11 2025

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

Sarment

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM to 9 AM PDT Wednesday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60
     NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to
     Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Gale Warning from 9 AM to 3 PM PDT Wednesday for SF Bay N of Bay
     Bridge.

     Gale Warning from 9 AM to 9 PM PDT Wednesday for Mry Bay-Pigeon
     Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt
     Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-
     10 nm.

     Gale Warning from 3 AM to 9 PM PDT Wednesday for Pt Arena to Pt
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 9 PM this evening to 3 AM PDT
     Wednesday for Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Sarment
MARINE...Murdock

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