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 18:30:06 PST 2025