FXUS66 KMTR 071150
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
350 AM PST Wed Jan 7 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 247 AM PST Wed Jan 7 2026
- High and dry pattern through the week with offshore flow and
cold overnight conditions
- Hazardous beach conditions at all Pacific Coast beaches
Thursday and Friday and again early next week
&&
.SHORT TERM...
Issued at 247 AM PST Wed Jan 7 2026
(Today and tonight)
Flooding continues for areas near and downstream of Mark West Creek
near Mirabel Heights as indicated by gauges and cameras. A Flood
Warning is in effect until 8 AM - this will likely be replaced by a
long duration Flood Advisory then as that is when it is forecast to
recede into minor flood stage. Residual troughiness will allow for a
dying cold front to skirt the region today. High clouds from this
feature will continue to stream into the region which will help
limit the extent of fog and stratus this morning. Sensible weather
wise, expect near normal temperatures and more gloomy conditions.
&&
.LONG TERM...
Issued at 247 AM PST Wed Jan 7 2026
(Thursday through Tuesday)
Global ensemble clusters are in agreement of some form of longwave
upper-level ridging dominating our long term forecast and beyond.
This will yield fair daytime conditions with cold overnight
conditions. An Extreme Cold Watch has been issued for most of the
area from 1 AM Friday to 9 AM Friday to cover the Thursday night
period. It's a bit of a nuanced forecast though as it isn't a cold
air mass bringing this along. In fact, 850 millibar temperatures are
forecast to warm near 7 degrees Celsius which is near the daily
mean. Some meteorological rule of thumb equates this to 45 degrees
at 5,000 feet. To figure out what's going on, we need to zoom out.
It is winter which means nights are long and therefore there is a
lot of time for radiational cooling to occur. As the Earth cools, a
shallow, stable layer develops near the surface, this is known as a
temperature inversion. Quantitatively, this is when temperature
increases with height, like in this case where we have ~0 degrees
Celsius at the surface and ~7 degrees Celsius at 5,000 feet. You can
think of it as a "cold lid". We are going to put a pin in this for
now. At the surface, high pressure will nose into the
California/Oregon border before ultimately building into the Great
Basin. Along the California Coast, a coastal trough will develop
which will facilitate offshore flow. Normally this would be a fire
weather concern, but we are way past that. We are going to keep our
fire weather thinking caps on though to understand why it is going
to be cold in some spots and not others. Circling back to our "cold
lid", offshore flow aloft will not be strong or turbulent enough to
break its seal. Some locations downslope of/in the higher terrain
are not in the Extreme Cold Watch as sufficient mixing will keep
them relatively warmer. The coldest spots will be Interior Monterey
and San Benito Counties, where below freezing temperatures are
possible. The North Bay Coast and San Francisco Peninsula Coast will
be moderated by the Pacific Ocean and downslope flow coming off of
the adjacent terrain. The Friday night period will be cold, but not
quite as cold as Thursday night. Overnight temperatures will slowly
rise through the weekend to become above criteria by the start of
next week.
&&
.AVIATION...
(12Z TAFS)
Issued at 342 AM PST Wed Jan 7 2026
A weak passing front is bringing in a mix of clouds, some of the
mid-high level, making it challenging to see developing sfc
clouds. That being said mostly VFR with pockets of MVFR with
lower cigs or patchy/transient fog. This will be the case through
this afternoon. Another weak boundary sweeps through later tonight
with stronger winds, clouds, and scattered showers. Lowest conf
as of now are precip chc tonight. Therefore, focused on winds and
lowering cigs to MVFR in the tafs.
Vicinity of SFO...VFR/MVFR through the AM rush. VFR this afternoon
with increasing winds. Did not issues an AWW, but could see
isolated gusts up to 30 kts.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Borderline of MVFR to VFR today. VFR
later this afternoon/evening. MVFR cigs return tonight with vcsh
possible.
&&
.MARINE...
(Today through Monday)
Issued at 247 AM PST Wed Jan 7 2026
A series of weak fronts will sweep through the region today and
tonight bringing increasing northerly winds. Fresh to strong
breezes will develop leading to hazardous conditions over the
waters. Additionally, a moderate period northwest swell will
arrive early Thursday and build through the day.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory from 1 AM Thursday to 10 PM PST Friday for
CAZ006-505-509-530.
Extreme Cold Watch from late Thursday night through Friday
morning for CAZ502-506-508-510-512>518-528>530.
Beach Hazards Statement from late tonight through Friday evening
for CAZ529.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 PM PST
Thursday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena
to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory from 3 PM this afternoon to 9 PM PST
Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt
Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...MM
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Wed Jan 7 08:30:03 PST 2026
From the National Weather Service
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