967
FXUS66 KMTR 281210
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
510 AM PDT Fri Mar 28 2025

...New AVIATION, MARINE, BEACHES...

.SYNOPSIS...
Issued at 303 AM PDT Fri Mar 28 2025

Cool conditions and hazardous beach conditions continue today. A
brief dry period Saturday precedes several rounds of rain and
wind slated for next week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 303 AM PDT Fri Mar 28 2025

Rain shower activity from a surface trough with upper level
support will continue to diminish through the morning. Rainfall
accumulation will be beneficial with locally
higher totals along the coast and in the higher terrain due to
orographic lift - the primary impact expected is wet roadways. Aside
from that, expect temperatures to remain below seasonal averages and
clouds to lift and decrease in coverage throughout the day as the
upper-level shortwave trough ejects east. While cold conditions
are not anticipated to be widespread enough for a Frost Advisory
tonight, isolated portions of the higher terrain in the North Bay
Interior Mountains, Eastern Santa Clara Hills, and Interior
Monterey and San Benito Counties are forecast to be in the 32 to
36 degree range. As always, please protect people, pets, plants,
and pipes. Last but certainly not least, a High Surf Advisory
remains in effect until 11 PM tonight for all Pacific Coast
beaches (sans Northern Monterey Bay as the area has a Beach
Hazards Statement in effect until 11 PM tonight). If you`re
planning on being near the Pacific Ocean, keep pets on a leash,
stay off of jetties and rocks, wear a life jacket, and never turn
your back on the ocean!

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 303 AM PDT Fri Mar 28 2025

Blink and you might miss the shortwave ridge tomorrow. While the
thermometer may read the same temperature today as it will tomorrow,
the lighter winds tomorrow will have the sensible weather feeling
warmer. Probably of more interest, tomorrow will be the driest day
of the next seven days. While not dry for quite a 24-hour period,
the first 75% of the day or so will be dry before a triple-point low
starts knocking on the doorstep. Sunday`s rainfall is expected to
take place within the warm sector, so steady, light, stratiform rain
is expected with a gradual northwest to southeast gradient of 0.50"
in the North Bay Mountains to 0.01" in the Interior Central Coast
respectively. Monday`s rainfall will be in the form of a cold front
so rainfall intensity can be expected to be relatively heavier over
a shorter period of time as compared to Sunday with a similar
(albeit sharper) northwest to southeast gradient of 0.75" in the
North Bay Mountains to 0.00" in the Interior Central Coast
respectively. These two rounds of rainfall will not necessarily have
a break in between them but overall are expected to remain
beneficial with wet roadways being the primary impact.
Unfortunately, confidence in the forecast drops off a cliff at this
point. While the official forecast has rain the next 7 days, just
how it happens is the tricky part. Global ensemble clusters are in
good agreement of troughing off the West Coast up until Tuesday when
there`s a 45% chance for zonal flow or even ridging to occur. This
is reflected nicely by the ECMWF and GEFS advertising staggering
differences in terms of moisture content with the former being much
drier than the latter. While there are deterministic solutions that
are bullish and advertise a strong atmospheric river (I`m looking at
you GFS), these should be considered outliers at this time as the 80
member ensemble mean of the ECMWF EPS and GEFS suggest brief periods
of time between Monday and Thursday with integrated water vapor
transport (IVT) values at or above 250 kg/ms which would suggest a
weak atmospheric river at best. Wind will also be on the increase
with the passage of each system and it goes without saying that the
strength of the systems will undoubtedly have an impact on wind
speeds.

&&

.AVIATION...
(12Z TAFS)
Issued at 441 AM PDT Fri Mar 28 2025

Ceilings have lifted to VFR across the area as the showers taper
off. This improving trend will continue through the day as a
moderate onshore breeze develops in the afternoon. Outside of some
possible patchy fog Saturday morning in the inland valleys, the
clearing trend will continue into Saturday before the next system
approaches on Sunday.

Vicinity of SFO...Moderate confidence in VFR ceilings gradually
lifting and breaking up through the day as a small amplitude ridge
moves over. There is a chance for MVFR ceilings around 15-18Z
according to model guidance, but it`s not included in the TAF. A
moderate westerly breeze will develop in the afternoon before
diminishing overnight. VFR conditions are expected through
Saturday before southerly winds, low clouds and rain return on
Sunday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR ceilings will continue to lift
through the morning with increasing sun breaks. A sea breeze will
bring moderate onshore winds through the afternoon before
diminishing overnight.

&&

.MARINE...
(Today through Wednesday)
Issued at 441 AM PDT Fri Mar 28 2025

Very high swell will gradually subside through the day as a low
amplitude short wave ridge builds. Moderate westerly winds will
diminish Saturday. By Sunday, an approaching low pressure system
will shift the winds to a strong southerly breeze with possible
gale force gusts and periods of rain.

&&

.BEACHES...
Issued at 441 AM PDT Fri Mar 28 2025

The long period northwest swell will continue to produce large
breaking waves up to 35 ft along the coast through the day today.
Buoys are currently reporting a 15 ft NW swell with a period of
around 15 seconds. The breaking waves will gradually diminish
through the day, although the hazard will peak around the mid-day
high tide. Large breaking waves will be focused on west and
northwest facing beaches, with enhanced rip currents expected on
all beaches. Inexperienced swimmers should stay out of the water.
Beachgoers should maintain a further stand-off distance from the
water than normal. Stay off of jetties and rocks, keep pets on a
leash, wear a life jacket, and never turn your back on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 11 PM PDT this evening for CAZ006-505-
     509-530.

     Beach Hazards Statement through this evening for CAZ529.

PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay.

     Small Craft Advisory until 9 AM PDT Saturday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
     Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Flynn
MARINE...Flynn

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