661
FXUS66 KMTR 260341
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
841 PM PDT Tue Mar 25 2025

...New UPDATE...

.SYNOPSIS...
Issued at 1244 PM PDT Tue Mar 25 2025

One more day of summertime warmth today with high temperatures
generally in the middle 70s to near 90. Seasonal temperatures and
light rain return tomorrow, with an impactful system possible this
weekend and early next week.

&&

.UPDATE...
Issued at 840 PM PDT Tue Mar 25 2025

While the calendar just flipped from Winter to Spring today felt
more like straight to Summer with southerly surges and record
breaking heat. While a few high clouds streamed over the region
today it wasn`t enough to prevent well above normal temperatures.
Many locations were approximately 10-20 degrees above normal. So
why? Lingering ridge of high pressure and a very warm airmass led
to the really warm temperatures. KOAK 00z sounding showed 850mb
temperatures at 16.4C. While that value wasn`t a daily record,
which is 17C, it was well above the 90th percentile. As such
temperatures soared into the 80s and 90s. Downtown San Francisco
fell just a few short of a daily record portions of the city still
reached the mid to upper 80s. Some of the warmest temperatures
were observed across the Santa Clara Valley and interior Central
Coast. The warmth along the coast ended in a classic fashion as a
southerly surge of marine layer clouds raced up the coastal
waters. Santa Cruz for instance saw a drop of 10+ degrees in about
1-2 hours as clouds moved inland.

For the rest of this evening and overnight: The marine layer will
continue to move northward and farther inland across the inland
valleys. Marine layer depth is pretty shallow now, but is expected
to deepen 2500-3000 feet. Given that depth and potential upslope
flow some coastal terrain areas could experience some drizzle
overnight. Patchy fog will also be possible with the most dense
fog along the immediate coast.

No update needed this evening.

MM

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 1244 PM PDT Tue Mar 25 2025

The skies are clear across most of the region as another day of
summertime temperatures and light winds prevails over the region.
High temperatures across the region range from the middle 80s to
near 90 for the inland valleys, the lower to middle 80s at the Bays,
and the 70s across the Pacific coast. Satellite imagery is showing a
southerly surge that is making its way along the Big Sur coast, and
we are continuing to monitor its northward progression. The stratus
is just making its way into the coastal regions, which when combined
to the extreme elevation differences along the Big Sur coast, and we
should get a better idea of how it will impact the region over the
next couple of hours. In contrast, it is looking increasingly likely
that the onset of high cloud cover that made today`s forecast more
uncertain this time yesterday should hold off until after sunset.

Assuming the current forecast holds, Minor HeatRisk is expected
across the region, corresponding to a minor risk of heat-related
illnesses for people extremely sensitive to heat exposure. Patches
of the Salinas Valley and Santa Cruz Mountains remain in Moderate
HeatRisk, corresponding to a moderate risk for heat related
illnesses for sensitive populations. Make sure to stay hydrated as
the warm temperatures continue!

Wednesday will see a pattern shift as the upper level ridge that has
provided us the last few days of warm weather moves out, and an
upper level trough impacts the Pacific Northwest. This will being
cooler and rainier conditions to the Bay Area and Central Coast.
High temperatures on Wednesday reach the upper 60s to the middle 70s
in the inland valleys of the Bay Area and Central Coast, and the
lower to middle 60s in the North Bay valleys, the Bayshore, and the
coastal regions. Light rain is expected across the North Bay and the
coastal ranges, with around a quarter to a half an inch across the
North Bay, a tenth to a quarter of an inch in the coastal ranges,
and up to a tenth of an inch in the area near San Francisco and
Oakland and the East bay and eastern Santa Clara hills. The interior
regions should cloud over, but are not expected to receive
measurable rain.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 1244 PM PDT Tue Mar 25 2025

Seasonal temperatures return to the region Thursday with highs in
the upper 50s into the 60s. Additional fringe rainfall is possible
through the early part of Friday with an additional quarter to half
an inch possible across the North Bay coastal ranges, generally up
to a quarter of an inch in the coastal ranges and the North Bay
valleys, and up to a tenth of an inch across the Bay Area and
coastal Santa Cruz and Monterey counties.

More impactful systems approach the Bay Area and Central Coast
starting Saturday night. The first system is expected to continue
through Sunday into the early part of Monday. Early estimates
suggest that rainfall totals could be modest from this system, with
the potential for totals up to a quarter an inch in the lower
elevations, significantly less in rain shadowed areas, and perhaps
as much as a half an inch in the higher elevations. This rain
amounts could be a precursor for an even more intense system for the
first couple days of April. Confidence is increasing in highly
significant rainfall for this time period. It is still too early to
pin down any specific rain totals, but ensemble model cluster
analysis continues to support widespread rain totals of at least 1-2
inches.

&&

.AVIATION...
(00Z TAFS)
Issued at 554 PM PDT Tue Mar 25 2025

Low clouds are moving in from the south along the coast and are
beginning to push inland around the Monterey Bay. Winds reduce into
the evening and these clouds will fill over the Monterey Bay
terminals into the early night with some pockets of fog. HAF will
see fog and IFR/LIFR CIGs fill as Monterey Bay terminals see CIGS
fall later into the night. Similar CIGs and pockets of fog will
affect the North Bay as well. MVFR CIGs will filter into the SF BAY
and fill over OAK and SFO into mid Wednesday morning. Southerly
winds increase into Wednesday with some slight clearing of CIGs. The
North Bay HAF look to keep their CIGS through Wednesday as the next
front begins to arrive and bring in light rain.

Vicinity of SFO...VFR with passing high clouds last into the mid
morning Wednesday before MVFR CIGs fill over the terminal. Expect
moderate into the night before turning light. Breezy southwest winds
build as CIGs fill over SFO Wednesday morning. These CIGs scatter
into the afternoon, but winds look to keep up. Expect MVFR CIGs and
light rain to return into that night.

SFO Bridge Approach...Similar to SFO

Monterey Bay Terminals...Low clouds are filling around the Monterey
Bay and will push into SNS through the evening. CIGs will make it to
MRY into the night as winds reduce. Pockets of Fog will form into
early Wednesday morning as CIGs fall to LIFR. These CIGs lift
slightly into the mid morning and exit Wednesday afternoon.

&&

.MARINE...
(Tonight through next Monday)
Issued at 554 PM PDT Tue Mar 25 2025

Light winds continue into the night before turning southerly and
becoming moderate to fresh by mid Wednesday. Seas will flux
between moderate and rough through Wednesday. Conditions
deteriorate Thursday when a west to northwest breezes become fresh
and seas become rough. Unsettled conditions continue through the
weekend and into the next work week as storm systems move through
the region.

&&

.BEACHES...
Issued at 1059 AM PDT Tue Mar 25 2025

A Beach Hazards Statement is in effect through Wednesday morning
for all Pacific Coast beaches. The warm conditions on land will do
nothing to the Pacific Ocean that is 51-57 degrees. In addition
to the cold water shock risk that is always present, there will be
an increased risk for sneaker waves and rip currents. Observe the
ocean for 20 minutes before you pick a spot on the beach, 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...Beach Hazards Statement through Wednesday morning for CAZ006-505-
     509-529-530.

PZ...None.
&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Murdock
MARINE...Murdock

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