155
FXUS66 KMTR 291748
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1048 AM PDT Sun Jun 29 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 923 AM PDT Sun Jun 29 2025

An upper low off the coast will keep onshore winds in place
through much of the week. Inland temperatures will cool back to
more seasonably warm weather with milder temperatures near the
coast as the marine layer will persist bringing night and morning
clouds.

&&

.UPDATE...
Issued at 923 AM PDT Sun Jun 29 2025

No updates planned for this morning. The low clouds have already
pulled back to the coast/beaches. Current marine layer depth is
around 1000 feet which has led to some morning fog and low cigs at
coastal airports. A nice Sunday in store for most of the Bay Area
with model guidance suggesting inland areas will have a modest
cool down as onshore flow increases this afternoon as upper low
off the coast gets a little closer. That low will have impacts
across the state the next few days that we`ll continue to monitor
closely. In the short term expect more convection over the Sierra
this afternoon with evening debris clouds from those storms
forecast to rotate across the North Bay this evening. The presence
of the low will help to induce more widespread convection Monday
and Tuesday for Northern California but at this time we are not
forecasting storms for the Bay Area with chances remaining less
than 5% over the far North Bay. We will continue to monitor for
any changes over the next several days. Otherwise the low will
cause an inland cool down early in the work week with near normal
temps beyond that.

&&

.SHORT TERM...
(Today and tonight)
Issued at 306 AM PDT Sun Jun 29 2025

The marine layer expansion is beginning and has made for a night of
increases coastal drizzle and fog, along with a much more far
reaching push of marine stratus inland. The Salinas Valley is
showing much more cloud intrusion than the last few nights and the
North Bay valleys are also beginning to see that cloud cover filter
in.

The feed and the thickness of the morning cloud cover will make it
slower to erode than previous days, but everywhere aside from the
immediate coast should see clearing skies around noon. This will
mean that some of those valleys that stayed clear in the morning
over the last few days will be slightly cooler from the reduced
amount of time in the sun. Highs will be largely the same for the
immediate coast (upper 50s to low 60s) as well as the interior (80s
and 90s for the far interior) but with slightly improved humidities.
Winds look to be moderate to breezy into the afternoon and evening
with cloud cover quick to rebuild in the evening.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 306 AM PDT Sun Jun 29 2025

The slow moving low and trough combo focuses over the region through
Sunday and just about grinds to a halt for Monday. This will keep of
the onshore flow and settle the marine layer to around 2000 ft and
allow for the marine influence to spread fairly far inland.

There is an interesting factor that this low is adding to the
forecast mix: the very slight potential for convection pulling into
the North Bay Mtns. Farther north as well as into the Sacramento
Valley, these chances look far better, but were`re still setting up
with a non-zero chance for thunderstorms in the North Bay (2-5%)
Monday and again Tuesday. Our chances remain lower because our
cooler and more stable environment will be working hard against
anything developing, or sustaining anything moving into Bay Area
from the north.

Outside of that excitement, the forecast really settles into a steady
daily pattern. The low and trough combo lasts into the mid week and
gets replaced by another troughing pattern. This will keep our
marine layer fairly well established around the 2000 ft mark with
the nightly inland pushes leading to far reaching low cloud cover.

So the pattern of:
-cloudy mornings with breezy, sunny afternoons inland areas
-constantly cloudy coasts
-warm, dry interior areas

continues through the forecast with only some slight variations on
the clearing times for the inland areas affecting high temperatures
and the change in flow slightly reducing fog and drizzle chances in
the second half of the work week.

And while some folk aren`t the biggest fans of June Gloom and "No
Sky July", remember this is keeping a fair moisture feed in the
area, and helps keep us out of critical fire danger. The cloud cover
also helps the night shift sleep better during the day, but that`s
more of a personal plus.

&&

.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.

&&

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

$$

SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...Kennedy
MARINE...Kennedy

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