Duncans Mills, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

230
FXUS66 KMTR 110452
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
952 PM PDT Sat May 10 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 217 PM PDT Sat May 10 2025

A pattern change begins on Sunday as upper level troughing sets up
over the Eastern Pac and then digs into PacNW. Cooler temperatures
are expected Sunday and Monday, with temperatures gradually warming
afterwards. Light rain and breezy winds will be possible with this
system, especially for areas north of the Golden Gate area, with
chances decreasing as you head south. Drier weather returns on
Tuesday.

&&

.UPDATE...
Issued at 840 PM PDT Sat May 10 2025

Quick recap of a very sunny Saturday - once again the weather
impacts were focused on temperatures. Ample insolation combined with
a warm airmass resulted in another day of above normal temperatures
across the Bay Area and Central Coast. KOAK 00z sounding confirmed
the warm airmass reporting another 850mb (18C) near the 90th
percentile. If you`re an avid reader of the AFD we reference 850mb
temps a lot for maximum temperature. As we head into our warm season
you might ask, why do we do it? It`s a good proxy for maximum
temperature potential under ideal conditions for a fully mixed lower
atmosphere. If an airmass is a certain temperature aloft we can take
that the theoretical air parcel aloft to the surface at a rate of
10C for every kilometer or 5.5F for every 1000 feet. So, for today`s
~18C at 850mb(~1.5km) we add 15C to the 18C for a value of 33C or
91F. That is a very simplified approach and there are many other
factors that play into Bay Area max temperatures. That being said,
far interior locations with in our forecast area that had a solid
mixed lower level and no marine influence easily reached in the
lower 90s. In fact, interior Central Coast over performed and hit
100 degrees at Bradley. One difference for today was the transition
area from far interior to the coast. Onshore flow increased
dramatically by late afternoon with SFO-SAC currently reaching
3.9mb and yesterday it was less than 1mb. The stronger onshore
flow increased winds and brought temperatures down along the coast
and a tad inland. Speaking of wind, a quick update was done to
the forecast to bump up winds this evening as gaps/passes/immediate
coast are already showing gusts over 25-30 mph.

No other changes to ongoing forecast...

Notable shift in sensible weather for Sunday with much cooler temps.
 See below...

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 217 PM PDT Sat May 10 2025

Key Messages

-High temperatures on Sunday will be 10 to 20 degrees cooler than
Saturday.
-Chances for rain slowly move in from the NW late Sunday into early
Monday, mainly for the North Bay Counties.

Stratus looks to return overnight and hug along our coast line,
while interior areas relatively clear. Any stratus that does develop
should eventually clear out by mid to late morning, leaving us with
a period of clear skies for the afternoon. The overall pattern
change begins on Sunday as upper level troughing sets up over the
Eastern Pac and then digs into PacNW throughout the day. Heights
will fall dropping putting our high temperatures 10 to 20 degrees
lower than they were on Saturday. Increasing clouds are expected
later in the day, with rain chances slowly creeping out from the NW.
Chances for rain gradually increase Sunday night into Monday morning
for the North Bay counties.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 217 PM PDT Sat May 10 2025

Key Messages

-Increasing chances for light rain through early Monday afternoon.
-The best chances for rain look to be north of the Golden Gate
region.
-Cooler temperatures Monday, warming trend begins Tuesday and
continues through the week.

Cool, breezy, and unsettled weather is expected on Monday as the
upper level low continues to dig and move eastward. Rain chances
look to increase through most of Monday morning before gradually
tapering off during the afternoon. Light and beneficial rain is
expected with the North Bay and San Francisco area seeing anywhere
between 0.05-0.25" of rain, with the larger amounts being observed
over the terrain. Elsewhere in the Bay Area and into the north
Central Coast, rainfall amounts look to be less than 0.10" of
accumulation.

As the low continues to track eastward Monday night into Tuesday,
we`ll be left in a post frontal environment. Ingredients for
thunderstorms are minimal, with instability likely being the
limiting factor. Current guidance suggests that should we clear we
should see at least some fair weather cumulus develop. In terms of
thunderstorms, confidence remains low, 10% OR less, in storms
developing. Should it happen, it seems areas with orographic lift
(terrain driven) have the best shot. This would be our interior
North Bay mountains, the Diablo and Gabilan ranges, and Cholame
hills. Opted to hint keep PoP and thunder out of the forecast at
this time but left some ghost PoP in to refer back to at later
forecasts should the signal become stronger. Once the trough clears
Tuesday, ridging builds in for mid to late week which will lead to
warming temperatures.

&&

.AVIATION...
(06Z TAFS)
Issued at 952 PM PDT Sat May 10 2025

Clear conditions /VFR/ prevail across the forecast area this
evening with dry air resulting in near high confidence VFR
continuing through the evening. The SFO-SAC pressure gradient has
strengthened to 4.2 mb while the ACV-SFO pressure gradient has
decreased to 3.2 mb. The marine layer depth varies from near sea
level to almost 1000 feet deep e.g. at the Fort Ord profiler.
Clouds increasing late Sunday night with a few showers arriving at
SFO and OAK Airports between 06z-12z Monday.

With a steady arrival of cooler air on northwest winds there`s
also an increasing probability of low clouds /IFR-MVFR/ developing
tonight and moving inland overnight to Sunday morning.

Vicinity of SFO...VFR continuing tonight until MVFR in low clouds
developing by 15z Sunday morning. West wind gradually diminishing
late tonight and Sunday morning, but quickly becoming increasingly
gusty to near 30 knots Sunday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR continuing through at least mid evening,
a moderate to high confidence forecast. MVFR in low clouds developing
late tonight and Sunday morning, mixing out to VFR by late morning.
Onshore winds 10 to 15 knots overnight, then winds gusty to 20 to 25
knots Sunday afternoon.

&&

.MARINE...
(Tonight through next Friday)
Issued at 942 PM PDT Sat May 10 2025

Moderate to fresh northwesterly breezes will persist across much
of the coastal waters through the weekend, with up to near gale
force gusts. Light rain will be possible on Monday as a front
moves across the region with diminishing winds in the wake of the
frontal passage. Winds increase once again toward the middle of
the upcoming week. Moderate seas continue through the end of the
forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Sunday for SF Bay N
     of Bay Bridge.

     Small Craft Advisory from 3 PM to 9 PM PDT Sunday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
     Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 3 AM PDT Monday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Canepa
MARINE...Canepa

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