159
FXUS66 KMTR 292045
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
145 PM PDT Sun Jun 29 2025

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

.SYNOPSIS...
Issued at 145 PM PDT Sun Jun 29 2025

The marine layer is around 1000 feet this afternoon and will
spread into the coastal valleys tonight while inland areas will
see a warm Sunday evening. An upper low offshore will deepen the
marine layer the next 24 hours and lead to slightly stronger
onshore winds along with an inland cooling trend. Instability
associated with the upper low looks to remain north and east of
the Bay Area through midweek. Another trough will approach by
Thursday and Friday keeping a deep marine layer along with inland
temperatures running near or slightly below normal.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 145 PM PDT Sun Jun 29 2025

A sunny and warm Sunday afternoon across the Bay Area with mainly
80s inland except widespread 90s interior Monterey county. The
marine layer is currently around 1000 feet and confined to the
coast. SFO-Sac gradient currently 2.4 mb but forecast to increase
this afternoon in response to inland heating and the offshore
upper low that should induce moderate seabreeze winds through the
Golden Gate and into the coastal valleys allowing for low clouds
to push locally inland overnight. Synoptic pattern features an
upper low offshore that may squeeze out some drizzle over the
ocean and along the coast late tonight into Monday morning.

Models show a slug of mid level instability (MUCape rotating
around offshore low) passing over the North Bay tonight but not
expecting any precip associated with this tonight.

Would expect marine layer to deepen slightly by Monday morning as
the offshore low gets a little closer to the coast. This should
help to increase onshore winds and keep inland temps mainly in the
80s once again for the interior Bay Area with 60s and 70s
coast/bays.

The upper low will bring some interesting weather to the state but
it looks to stay north and east of the Bay Area with thunderstorms
and associated fire weather/lightning concerns across the
Northern Sierra and the coastal ranges from roughly Clear Lake
northward. Models still show 2-5% probs of thunder for northern
Sonoma/Napa so cant completely rule threat out but climatology and
pattern recognition suggests the main threat remains to our
north, nonetheless we will continue to monitor.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 145 PM PDT Sun Jun 29 2025

Upper low of interest should be over Big Sur by Tuesday and lead
to a deep marine layer locally from the Golden Gate to Big Sur.
Instability associated with the upper low will be over the Sierra
and northern mountains from the coastal ranges up towards Mt
Shasta. The low will keep winds onshore and along with the deep
marine layer no real hot weather is forecast for the region.

The main trough axis finally pushes inland and the upper flow will
turn WSW witch will end a lot of the convective threat across the
state (except east of the Sierra crest).

Looks like another trough arrives by Thursday or Friday. This one
looks more progressive with some cool (in relative terms) air
aloft. This suggests no hot temp concerns locally for the start of
the holiday weekend. The trough may be strong enough to mix out
the marine layer or at least allow for partial clearing each
afternoon and evening. Main message then for the holiday weekend
looks to be dry with near or below normal temps.

Some hint of more significant ridging and inland heat by around
July 7-8th which would match climatology as the 4-corners ridge
starts to build but far enough away to keep confidence low to
medium as several 500 mb clusters still show troughing solutions.

&&

.AVIATION...
(18Z TAFS)
Issued at 1048 AM PDT Sun Jun 29 2025

Stratus coverage is diminishing along the direct coastline only HAF
reporting BKN cloud cover still. The marine layer looks to deepen to
1500-2000 ft tonight which will allow for more widespread cloud
cover tonight. Low to moderate confidence in stratus reaching STS,
APC, OAK and moderate to high confidence in stratus reaching HAF,
MRY, and SNS. Current thinking is that stratus will not reach SFO,
SJC, and LVK overnight. Guidance does indicate some potential for
SFO and SJC to become overcast later in the night (closer to 10-12Z)
but confidence is low. Localized fog is possible in the North Bay
Valleys and directly along the coastline which may result in lowered
visibilities and ceilings if fog forms in the vicinity of the
airport. Moderate onshore winds continue during the afternoon and
evening before winds ease and become light to variable at most sites
overnight.

Vicinity of SFO...VFR with low potential for MVFR-IFR CIGs to
develop overnight. LAMP probabilistic guidance shows increased
potential for MVFR-IFR CIGs to develop after 10Z and to persist
through 18Z tomorrow morning. However, high resolution models (HRRR,
NAMNest) keep SFO clear through the entire TAF period. Current
thinking is leaning more towards the HRRR and NAMNest where stratus
will fill into the SF Bay, impacting OAK, but is not expected to
reach SFO. Winds stay onshore through the afternoon/evening but look
to briefly shift more northerly to slightly northeasterly early
tomorrow morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with an early return of LIFR
conditions expected this evening. CIGs look to return between 02-03Z
with visibilities expected to drop overnight. Highest confidence in
fog potentially impacting MRY after 09Z with slightly lower
confidence that fog will impact SNS after 12Z. Conditions may start
to improve as early as 17/18Z at SNS but are likely to improve
closer to 19/20Z at MRY. &&

.MARINE...
(Today through Friday)
Issued at 1048 AM PDT Sun Jun 29 2025

Significant wave heights and winds continue to ease through early
Tuesday morning. Locally breezy, fresh to strong, northwesterly
gusts continue across the outer coastal waters with emphasis on
the far northern outer waters north of Point Reyes. Southerly to
southwesterly winds continue across the inner coastal waters north
of Point Pinos. Significant wave heights begin to build again on
Tuesday with strong northwesterly breezes and moderate to rough
seas that will persist into late next week.

&&

.MARINE...
(Today through Friday)
Issued at 1048 AM PDT Sun Jun 29 2025

Significant wave heights and winds continue to ease through early
Tuesday morning. Locally breezy, fresh to strong, northwesterly
gusts continue across the outer coastal waters with emphasis on
the far northern outer waters north of Point Reyes. Southerly to
southwesterly winds continue across the inner coastal waters north
of Point Pinos. Significant wave heights begin to build again on
Tuesday with strong northwesterly breezes and moderate to rough
seas that will persist into late next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RW
LONG TERM....RW
AVIATION...Kennedy
MARINE...Kennedy

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