FXUS66 KMTR 072019
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1219 PM PST Sun Dec 7 2025
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1218 PM PST Sun Dec 7 2025
- Benign conditions through the next seven days with no
precipitation expected and a gradual warming trend through the
later part of the week
- Impacts from Tule Fog continue in the North Bay and interior
East Bay valleys, with potential for expansion across the rest
of the Bay Area overnight
- Next chance for rain lies slightly beyond the 7-day outlook
&&
.SHORT TERM...
Issued at 1218 PM PST Sun Dec 7 2025
(This evening through Monday)
Today is looking to be very similar to yesterday, right down to the
satellite imagery showing outgrowth from the Tule Fog across the Bay
Area, slowly dissipating south of the Golden Gate and west of the
Berkeley-San Leandro Hills and the eastern Santa Clara Mountains,
and lingering across the North Bay and interior East Bay valleys.
Indeed, if you compared the current satellite image and the one from
yesterday, you could only them apart by the lack of coastal stratus
today. As a point of curiosity, while there are no radiosonde
observations over the Central Valley, aircraft soundings from the
region suggest that the saturated lower atmosphere -- the "Tule fog"
layer, if you will -- extends 1500-2000 feet above the ground. The
Central Coast remains mainly clear.
The remarkably similar evolution of the stratus from yesterday
through today has lowered confidence in the clearing of stratus from
the Santa Rosa Plain and the rest of the North Bay valleys. I've
tamped down the high temperatures today even further in those
regions, into the upper 40s to the lower 50s, and even then the
expected highs are still a little warmer than the observed highs
yesterday. Across the rest of the region, temperatures range from
the middle 50s to lower 60s across the Bayshore, the Bay Area
Pacific Coast and the Santa Clara Valley, while the sun-blessed
Central Coast sees highs in the lower to middle 60s in the Monterey
Bay region and the Hollister area, and the upper 60s to lower 70s
inland.
Tomorrow, the ridge over the West Coast will strengthen and continue
a general warming trend across the region. For the Central Coast,
the temperature forecast should be similar to today's. The
uncertainty increases across the Bay Area and especially in the
North and East Bays, where the impacts of the building ridge on the
Tule Fog remain uncertain. In general, a building ridge will tend to
compress the inversion layer, and limit the extent that the Tule Fog
can extend across the region. (We see this happen during our marine
layer season as well, when building ridges compress the marine layer
and prevent it from coming inland.) If the inversion layer does
compress enough, the Tule Fog could find itself hitting a proverbial
wall before it reaches the Bay Area. On the flip side, for those
areas still impacted by the Tule Fog, ceilings and visibilities will
tend to drop. This makes the temperature forecasts highly uncertain.
For now, tamped down the temperatures slightly so that the North and
East Bay valleys see highs in the middle 50s to lower 60s, while the
rest of the Bay Area valleys see highs in the lower to middle
60s, but this might be quite optimistic indeed.
&&
.LONG TERM...
Issued at 1218 PM PST Sun Dec 7 2025
(Monday night through next Saturday)
Ridiculously resilient ridging will dominate the weather pattern
through the rest of the week with the ridge crawling through the
Western United States, such that over the next 6 days the ridge axis
moves from just off the coast of the Pacific Northwest to the Oregon-
Idaho border area. Over the Central Coast the impacts are most
certain with a gradual warming trend in the forecast. The warmest
days are expected Wednesday through Saturday with highs reaching the
upper 60s to the middle 70s across the inland valleys. The Bay Area
in general and the North and East Bay valleys in particular remain
tied to the evolution of the Tule Fog. Impacts are expected to
persist into the early part of the work week before diminishing with
the continuing ridging across the region.
The pattern change for the middle of the month is beginning to come
into the very end of the 7 day outlook. The early indications are
pointing more towards a zonal flow pattern for the Western United
States and any rain storms that develop generally being deflected
into the Pacific Northwest. Beyond the 7-day outlook, the ensemble
model clusters suggest that a return to a wetter pattern is possible
around 9-10 days out, and the CPC's 8-14 day outlook shows a slight
lean towards rainfall totals above seasonal averages for the third
week of December. I have heard that before this month...
&&
.AVIATION...
(18Z TAFS)
Issued at 955 AM PST Sun Dec 7 2025
Tough forecast given the Tule fog and associated stratus have not
been handled well by the models. In fact, most of them for today are
fairly optimistic, which seems unlikely for much of our service Bay
Area terminals. The marine layer looks to be 1000-1500ft, with the
Valley being socked in as of this discussion. Expect cloudy
conditions to prevail for most sites, with CIGS varying from LIFR to
IFR. The exception might be KOAK, KSFO, and KSJC where onshore flow
might be able to mix things out. Where skies are clear, KHAF,
elevations above 1500ft, and the majority of the Central Coast, VFR
conditions will prevail.
Vicinity of SFO...Low to medium confidence in the forecast here
as most models have indicated some clearing by now and what we
have seen so far is a slight lift in CIGs. Satellite imagery
shows some clearing over the San Francisco Bay, but outside of
that there doesn't appear to be much movement. The most
pessimistic of forecasts looks to be the MOS guidance from the EC,
which has loosely been incorporated in the TAF for clearing
around 21Z. After that, opted to keep the previous forecaster's
TAFs in shape if the onshore flow pans out. Should it not, and we
stay socked in. The question if that happens will be how long do
we stay with IFR cigs? Low to medium confidence on this forecast.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Light and variable offshore winds become
onshore by this afternoon, before circling back to offshore or light
variable tonight. No VIS or CIG concerns, thus VFR prevail. &&
.MARINE...
(Today through Friday)
Issued at 900 AM PST Sun Dec 7 2025
Moderate to fresh north to northwest winds hold for much of the
waters today with strong gusts focused on the southern waters.
Moderate seas with wave heights 6 to 8 feet across the outer
waters today, subsiding to around 4 to 6 feet for Monday. Winds
increase on Tuesday, with strong to near gale force gusts possible
for much of the waters. A new, long period northwesterly swell is
anticipated by Wednesday of next week.
&&
.MARINE...
(Today through Friday)
Issued at 900 AM PST Sun Dec 7 2025
Moderate to fresh north to northwest winds hold for much of the
waters today with strong gusts focused on the southern waters.
Moderate seas with wave heights 6 to 8 feet across the outer
waters today, subsiding to around 4 to 6 feet for Monday. Winds
increase on Tuesday, with strong to near gale force gusts possible
for much of the waters. A new, long period northwesterly swell is
anticipated by Wednesday of next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 3 PM PST this afternoon for CAZ006-
506-508-529-530.
PZ...Small Craft Advisory from 3 PM Monday to 3 AM PST Tuesday for
Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60
NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60
NM.
Small Craft Advisory until 9 PM PST this evening for Pigeon Pt
to Pt Pinos 0-10 nm.
Small Craft Advisory until 3 AM PST Tuesday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 PM PST this evening for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...KR
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Sun Dec 7 12:30:03 PST 2025
From the National Weather Service
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