419
FXUS66 KMTR 170421
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
921 PM PDT Thu Oct 16 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 144 PM PDT Thu Oct 16 2025

 - Warming and drying trend through Saturday

 - Offshore winds in the higher elevations tonight and again Friday
   night into Saturday

 - Long period northwesterly swell will bring an increased risk of
   sneaker waves and rip currents to Pacific Coast beaches Friday
   night and into Saturday

&&

.UPDATE...
Issued at 745 PM PDT Thu Oct 16 2025

Warmer across the region thanks to abundant sunshine and a
warming airmass today. Highs rose 5 to 10 degrees from Wednesday
to Thursday with max temps reaching the 60s and 70s. Despite the
overall warm up the hills/mts across the Central Coast were still
chilly and stayed in the 50s.

Normally mentioning offshore flow in October would be a fire
weather concern, but recent rains have helped those concerns.
Synoptically speaking, offshore flow began to develop earlier
today with SFO-WMC now approaching -4.5mb. Obs over the higher
terrain are already showing NE flow with occasional gusts over 20
mph. The offshore gradient is only expected to peak in the -5 to
-6mb range tonight or weak/moderate category. While breezy in the
hills and lowering RH not expecting any major impacts. If
anything, it will help to disrupt the marine layer. Most notable
offshore flow will be over the N Bay Mts and E Bay Hills.

No update needed.

&&

.SHORT TERM...
Issued at 144 PM PDT Thu Oct 16 2025
(This evening through Friday)

Building surface high pressure across the eastern Pacific will
result in a warming trend over the next few days as it builds into
the Great Basin on Friday. Also, a coastal trough will develop over
the California coast. This will result in north-northeasterly winds
across the higher terrain, especially across the North Bay overnight
tonight and into early Friday morning. Wind gusts will generally
remain below 35 mph in the highest peaks of the North Bay. However,
fire weather concerns will be limited by the offshore winds not
being overly strong and recent rainfall.

There is about a 15-30% chance for fog over the Bay Shoreline early
Friday morning, yet confidence is not high enough to include in the
official forecast. Temperatures Friday morning will bottom out in
the 40s across the North Bay and southern interior Central Coast
with low 50s elsewhere.

Any low clouds or fog that do develop will likely dissipate by
around 10 AM Friday. The offshore flow aloft will result in warming
temperatures by Friday afternoon when non-coastal areas warm into
the 70s with low-to-mid 60s at the coast. These temperatures will be
up to 5 degrees F above seasonal averages under mostly sunny skies.

&&

.LONG TERM...
Issued at 144 PM PDT Thu Oct 16 2025
(Friday night through next Wednesday)

Friday night and into Saturday morning, offshore winds will persist
in higher elevations across the North Bay, weaker elsewhere and
weaker than what we are expecting tonight with temperatures mostly
in the 50s to upper 40s in the North Bay and southern interior
Central Coast.

On Sunday, a cut-off mid/upper level low will develop off of
southern California and will result in less of a cool down than
previously expected. This would act to block the approaching upper
level trough from pushing a cold front across the Bay Area and
Central Coast. However, temperatures are forecast to cool by a few
degrees on Sunday. Still expecting offshore winds to develop in the
higher terrain as the trough moves into the Intermountain West
Monday and Tuesday. Mostly zonal flow aloft is expected through the
remainder of next week across the Bay Area and Central Coast. Thus,
temperatures are forecast to be near normal for this time of year.

Longer range guidance suggests a wetter pattern developing by next
weekend (October 25th and 26th) along with cooler temperatures. This
is reflected in both the 6-10 and 8-14 Day Outlooks issued by the
Climate Prediction Center. Stay tuned...

&&

.AVIATION...
(06Z TAFS)
Issued at 921 PM PDT Thu Oct 16 2025

VFR is forecast through the evening except for patchy low clouds
/MVFR-IFR/ developing along the immediate coastline. The evening
00z Oakland upper air sounding shows a precipitable water of 0.54"
(25th percentile for the time of year) with a good radiative
cooling window open i.e. drier layer above the boundary layer for
nocturnal longwave radiative cooling to space. A loss of heat to
space will cool temperatures near surface dewpoint temps (measure
of water vapor) tonight and Friday morning with a few areas of fog
including dense fog probable (20-50%, greater than 50% over the
SF Bay early Friday morning). ECMWF and GFS show cirrus clouds
arriving from the north tonight and Friday, which may slow
radiative cooling a little overnight. Diurnal surface heating and
mixing results in VFR redeveloping Friday.

Vicinity of SFO...VFR continues through the evening. Radiative
cooling will result in low clouds and mist/fog /IFR/ 11z-15z
Friday with IFR prevailing until 18z Friday. VFR thereafter for
Friday. West-northwest wind 10 to 15 knots, decreasing and
becoming light and variable to light easterly Friday morning to
mid afternoon. West wind near 10 knots redevelops by late Friday
afternoon or early evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR however SCT-BKN low clouds /MVFR-IFR/
will form nearby the terminals during the evening, with increasing
probability of LIFR-IFR in fog and low clouds late tonight and
early Friday morning. Light east to southeasterly winds tonight
increasing to 5 to 10 knots perhaps up to 15 knots in the Salinas
Valley late tonight and Friday morning; cool air drainage winds
will help to mix out the fog /LIFR-IFR/ earlier than usual Friday
morning. By late afternoon winds shift to onshore 5 to 10 knots.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 918 PM PDT Thu Oct 16 2025

Moderate northwesterly breezes will continue through the end of
this week. A few gusts will be strong, favoring the outer waters
and south of Pigeon Point for the inner waters. A longer period
northwesterly swell arrives this weekend 7 to 10 feet at 15
seconds.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Friday evening through Saturday
     evening for CAZ006-505-509-529-530.

PZ...Small Craft Advisory until 3 PM PDT Friday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Canepa
MARINE...Canepa

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