FXUS66 KMTR 122332
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
332 PM PST Fri Dec 12 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1248 PM PST Fri Dec 12 2025
- Hazardous beach conditions through the evening
- Impacts from Tule Fog continue in the North Bay and interior
East Bay valleys
- Wetter conditions expected next week
&&
.SHORT TERM...
Issued at 1248 PM PST Fri Dec 12 2025
(This evening through Saturday)
Persistent stratus and fog continues across the valleys of the North
Bay and interior East Bay, with the clouds continuing to mix out
throughout the afternoon and into the early evening hours, when the
Tule Fog outgrowth returns to the Bay Area. To the south, a
southerly surge is developing to the west of San Luis Obispo County,
and will travel northwards along the Big Sur coast, flow into the
Monterey Bay region, and progress along the San Mateo coast through
the evening and overnight hours. Continuing to opt for a more
persistent forecast for high temperatures today, with highs in the
Central Coast valleys reaching the lower to middle 70s, the Bay Area
valleys reaching the upper 50s to lower 60s barring the northern and
eastern parts of the interior East Bay, where highs reach the middle
40s to near 50, and highs across the higher elevations into the
lower to middle 70s. Overnight, expect lows in the upper 30s to
middle 40s for the valley regions, and the middle 40s to the lower
50s in the higher elevations. Dense Fog Advisories may need to be
issued early Saturday morning for the inland valleys, but also the
immediate coast depending on the evolution of the Tule Fog and
southerly surge through the next day.
By Saturday, the ridge that has brought us the last few days of
stable conditions will begin move off to the east, with the coastal
stratus retreating to the immediate coastal region. How the Tule Fog
will react to the change isn't all too clear. The current forecast
shows a similar clearing pattern to today's. High temperatures are
currently expected to remain nearly the same as today's in the lower
elevations, perhaps a couple of degrees cooler in the higher
elevations.
&&
.LONG TERM...
Issued at 1248 PM PST Fri Dec 12 2025
(Saturday night through next Thursday)
As we head into the early part of next week, the ridge continues to
move to the east and a pattern change brings more zonal flow to the
region by Tuesday. This new pattern should help scour out the Tule
Fog and, when combined with a plume of moisture with PWAT values up
to 1.2 inches, brings a chance of light rain to the region Tuesday
and Wednesday, focused on the North Bay. A weak ridge will move
through the state on Thursday and Friday, but the overall flow
should remain generally zonal and lingering showers and drizzle are
possible from remnant moisture in the region.
Beyond the 7-day outlook, the forecast points towards another round
of wet weather across the region for the weekend of the 20th and
21st as a deep trough in the eastern Pacific coincides with another
plume of moisture moving through the West Coast. The CPC outlooks
are leaning towards precipitation totals above the seasonal average
in their latest 6-10 day outlooks (from December 18th to the 22nd,
55-70% probability), giving the region a moderate chance for heavy
rain and high winds (40-60% probability of total rainfall and
sustained winds reaching the 85th percentile of the seasonal
distribution) starting on the 20th. For context, when taking the
long-term averages, December is the wettest month for downtown San
Francisco with monthly average precipitation of 4.76 inches. We have
not seen a drop of rain since the 20th of November, and for the 6-10
day outlook, the expected rainfall total lies somewhere around three
quarters of an inch of rain. The chances for rain don't stop that
weekend: CPC outlooks maintain the lean towards precipitation totals
above seasonal averages in the 8-14 day outlook (December 20th-26th,
seasonal average of over an inch of rainfall at downtown San
Francisco), the moderate chances for heavy rain and high winds
mentioned earlier in this paragraph extend through the 26th, and the
ensemble mean products suggest a lingering trough in the eastern
Pacific through this period, a pretty notable signal especially this
far out into the forecast.
&&
.AVIATION...
(00Z TAFS)
Issued at 332 PM PST Fri Dec 12 2025
Currently VFR but fog and stratus remain entrenched along the Delta
and in portions of the interior East Bay. Kept the timing of fog
returning to STS, APC, LVK, and SJC about the same as the last night
following a persistence forecast. The one thing to watch for is that
more expansive fog cover across the East Bay tonight than at this
time last night may result in a slightly faster arrival time of fog
to LVK and SJC. For coastal sites HAF, MRY, and SNS, a southerly
surge of marine stratus will bring a return of IFR-LIFR conditions
overnight. This is likely to at least temporarily bring fog to MRY
and SNS. Winds generally stay light through the TAF period but
maintained some gustier conditions at APC given the similar setup
tonight compared to last night.
Vicinity of SFO...VFR. Not expecting Tule Fog to reach SFO tonight.
The one question would be if low clouds from the southerly surge
will be able to reach SFO by mid to late tomorrow morning.
Forecaster is leaning more towards the HREF which supports SFO
staying VFR through tomorrow morning but suggests clouds will return
by late tomorrow evening, at the end of or just after the end of the
current TAF period. Winds generally remain light and offshore
through the TAF period with periods of more variable winds overnight.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR becoming IFR-LIFR as a southerly surge
arrives bringing low clouds and fog. Confidence is slightly higher
that fog will impact SNS than MRY but there is some potential for
both to at least temporarily see fog tomorrow morning. LAMP guidance
leans on the side of MVFR-IFR conditions at MRY but there is still a
low chance of LIFR conditions developing. Winds remain light at MRY
through the TAF period. Moderate SE drainage winds develop at SNS
overnight with light NNW to N winds otherwise expected.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 332 PM PST Fri Dec 12 2025
Gentle northeasterly winds will gradually shift to southerly by
Saturday morning. Moderate seas will subside to a slight 3 feet
from Saturday through Monday before winds increase out of the
northwest by Monday. A westerly swell will return by Tuesday and
build through the remainder of next week. There is a chance for
light rain for much of the upcoming week.
&&
.BEACHES...
Issued at 1214 AM PST Fri Dec 12 2025
Long period NW swell is causing hazardous beach conditions
Friday. This energy brings strong rip currents, an increased risk
for sneaker waves, and large breaking waves. This coincides with
nice warm weather, which will likely lure more people to the beach
under a false sense of security. A Beach Hazard Statement is in
effect through Friday evening. Respect the power of the ocean and
never turn your back on it.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 10 PM PST this evening for CAZ006-
505-509-529-530.
PZ...None.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Kennedy
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Fri Dec 12 16:30:03 PST 2025
From the National Weather Service
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