FXUS66 KMTR 090549
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
949 PM PST Mon Dec 8 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 243 PM PST Mon Dec 8 2025
- Tule fog and stratus return tonight for Bay Area valleys.
- Quiet and benign weather this week.
- Next chance for rain is around December 15.
&&
.UPDATE...
Issued at 855 PM PST Mon Dec 8 2025
A strong 500 mb high pressure system (585 decameter height)
remains over the forecast area. This continues to result in dry
weather. Large scale compressional warming of air within the high
continues to result in close to 90th percentile (or slightly
greater) temperatures at each of the mandatory pressure levels
from 925 mb to 500 mb on the Oakland upper air sounding for the
time of year. This warmth is aloft, with milder to warmer
temperatures also over our forecast area at ground level where it
remains clear/sunny during the day, an early December sun angle
heat input reaching the ground connecting and mixing with warm
air availability just overhead near the temperature inversion.
However, this air mass stability is also resulting in a much
different story near and at ground level where fog and stratus
prevail much if not all day e.g. in the East Bay and the North Bay
valleys, also reaching the San Francisco Peninsula on mainly
light offshore winds; it's been markedly chillier on a daily basis
in these areas since November 25th.
For the time being high pressure remains in control of our area's
weather, which extends through the rest of the week with some
weakening of the high over the weekend, but only marginally with
500 mb heights barely lowering below 580 decameters.
&&
.SHORT TERM...
Issued at 243 PM PST Mon Dec 8 2025
(This evening through Tuesday)
The stagnant pattern continues with the story being cloudy
conditions returning tonight for areas that cleared around the Bay
Area and clear conditions for much of the Central Coast. This should
keep low temperatures generally in the 40s for Bay Area counties and
Santa Cruz County. Elsewhere in the Central Coast, lows will vary
from the upper 30s to low 40s for the interior portions, while c
coastal areas sit closer to the mid 40s. A new forecast challenge
also arrives for tonight as temperatures were a bit chillier than
expected last night for the northern Salinas Valley and along the
coast of the southern Monterey Bay area. For now kept NBM in for
the lows; however, should temps drop like last night they may need
to be adjusted a few degrees cooler.
&&
.LONG TERM...
Issued at 243 PM PST Mon Dec 8 2025
(Tuesday night through next Sunday)
High pressure holds through the week, leading to dry conditions
through the weekend. Temperatures should warm by mid week, before
cooling a bit again over the weekend. The next chance for rain looks
to be around December 15, where the NBM favors the best chances of
rain around the North Bay with a 15-20% expanding to the East and
South Bay counties and into Santa Cruz County. Ensembles do show the
ridge flattening some which could allow a front to make it into the
region. The details will likely change, so stay tuned.
&&
.AVIATION...
(06Z TAFS)
Issued at 948 PM PST Mon Dec 8 2025
Low clouds and fog have reformed in the North Bay and interior East
Bay. SFO and SJC see CIGs arrive in the late night with some slight
reductions in visibilities. Winds stay mostly light to moderate
through the TAF period, with wind directions determined by more
localized affects. Cloud cover and fog will be slow to erode into
Wednesday afternoon, but conditions look to improve into the late
afternoon. However, the North and East Bay will continue to struggle
with low clouds and fog, causing some doubt for clearing at APC. As
cloud cover erodes, pockets of haze will affect much of the region.
Winds reduce again into Wednesday evening with fog and low cloud
looking again to reform in the North Bay and interior East Bay.
Vicinity of SFO...VFR lasts into the late night. Winds become
lighter into the night with scattered low clouds building into the
area, along with some slight reduction in visibilities. IFR level
CIGs fill into the late night with some weak easterly winds. Cloud
cover thins into the afternoon, but winds stay light and turn
slightly more northerly. These wind look to become light and variable
into the late evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR through the TAF period. Winds stay
light for MRY through the TAF period, while SNS sees moderate
westnorthwest rebuild into Wednesday afternoon. These winds become
light and variable into that night.
&&
.MARINE...
(Tonight through next Sunday)
Issued at 948 PM PST Mon Dec 8 2025
North and northwest flow continues with moderate to fresh winds
continuing south of Point Sur. Winds increase to a strong breeze
Tuesday into mid week across the outer waters. A new, long period
northwesterly swell is expected by midday Wednesday,lasting into
the early weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PST Tuesday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...Murdock
MARINE...Murdock
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Tue Dec 9 00:30:04 PST 2025
From the National Weather Service
|