San Mateo, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

818
FXUS66 KMTR 140712
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1212 AM PDT Mon Jul 14 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1210 AM PDT Mon Jul 14 2025

 - Temperatures near to slightly below seasonal averages with a
   more noticeable cooling trend beginning Tuesday.

 - Localized elevated fire weather threat continues across the
   higher elevations.

 - Slight warming trend later this week into the upcoming weekend.

&&

.SHORT TERM...
Issued at 1210 AM PDT Mon Jul 14 2025
(Today and tonight)

Satellite imagery depicts the coastal stratus layer streaming into
the Sonoma County valleys, curling from the East Bay across the
southern San Francisco Bay, and blanketing the Monterey Bay region
and Salinas Valley. Expect some additional inland stratus
development through the rest of the morning before the clouds
retreat to the immediate coast after sunrise. The temperature
forecast will feel like a bit of deja vu from the last couple of
days, with low temperatures this morning ranging from the middle to
upper 50s across the lower elevations and the 60s to lower 70s in
the higher elevations. Meanwhile, high temperatures range from the
80s to the lower 90s inland with temperatures near 100 in the
warmest spots, the 70s and lower 80s near the Bays, and the upper
50s to lower 60s along the Pacific Coast. Breezy onshore winds
develop in the afternoon and evening with wind gusts up to 25 mph
through favored gaps and passes and within the Salinas Valley.

Localized elevated fire weather threat continues across areas above
and inland of the marine layer`s influence. The combination of dry
daytime humidities of around 20-35%, poor overnight recoveries of 25-
40%, and localized gusts to 25 mph will be the main factors behind
the elevated threat. However, the winds will remain onshore, leading
to the fire weather threat being diurnally driven, especially in the
foothills where lighter winds and good overnight recoveries are
expected each night.

&&

.LONG TERM...
Issued at 1210 AM PDT Mon Jul 14 2025
(Tuesday through Sunday)

Late today, a shortwave trough, or perhaps a weak cutoff low,
develops into the Pacific Northwest and the northern Rockies,
pushing the ridge axis towards the west and north and causing a
noticeable cooling trend to begin tomorrow and lasting for the
following two days. High temperatures drop into the middle 70s to
middle 80s inland and the upper 60s to the middle 70s along the
Bayshore, with the coast remaining rather stable at the upper 50s
to lower 60s.

A slight warming trend is expected heading towards the upcoming
weekend. Ensemble model cluster analysis does feature scenarios
where troughing and ridging develop over the northwestern United
States through the upcoming weekend. However, in terms of sensible
weather, most of the impacts from any deviation in the weather
pattern will be felt across the Pacific Northwest and northern
Rockies, with muted impacts across central California. Although the
exact details are still subject to variation, the current forecast
sees temperatures across the inland valleys rising to the 80s and
lower 90s, up to the upper 90s in the warmest locations.

&&

.AVIATION...
(06Z TAFS)
Issued at 1011 PM PDT Sun Jul 13 2025

The onshore SFO-SAC 3.2 mb predominates with decent inland
stratus and fog intrusion potential tonight and Monday morning.
Over the CA coastal waters and offshore waters a weak and nearly
stationary surface trough persists. Coastal profilers from Bodega
Bay to Point Sur show very little change in the marine layer
depth, varying from 1300 to 1500 feet. Recent air temps at San
Francisco downtown and Oakland downtown are ~ 1/2 degree
Fahrenheit cooler than this time 24 hours ago, it may not sound
like much and it isn`t, but it may represent a slight change in
surface air mass characteristics advected in from the coastal
waters. The overall combination of a clear sky above the marine
layer with this evening`s 00z Oakland sounding precipitable water
lower at 0.51" (10th percentile for time of year) supports
improved nocturnal radiational cooling which while there is a
surface influx of slightly cooler air within the marine layer may
set up for a longer duration stratus and fog intrusion to mix out
Monday. For the 06z TAFs decided to slightly extend ceiling
forecasts over model output by an hour or two.

Only minor temperature fluctuations are forecast aloft specifically
in the vicinity of 925 mb (~ 2500 feet) tonight and Monday. Thermal
ridging aloft otherwise continues in the lower to mid levels tonight
and Monday. The 06z TAFs still mainly lean toward persistence, expect
an ongoing inland intrusion of stratus, patchy fog and redevelopment
of at least patchy light coastal drizzle /IFR-LIFR/ tonight and Monday
morning. Lower level temps at ~ 2500 feet begin to cool Monday night
with 2 Celsius to 3 Celsius cooling by 12z Tuesday morning per 18z
NAM output. Lower level cool air advection should begin to deepen
the marine layer setting up for a deeper inland stratus intrusion
Monday night and Tuesday morning.

Vicinity of SFO...Amended the earlier TAF forecast to extend VFR
conditions just a little longer tonight, satellite imagery shows
stratus curling around from the Golden Gate to Oakland, a classic
summer set up for later arrival at SFO. Forecast tempo IFR 08z-10z,
then IFR prevailing. RAP model is indicating high humidity, low
ceiling and fog potential tonight/Monday morning. Conditions may
not lift to MVFR-VFR until Monday early afternoon. West-northwest
wind tonight. West to northwest wind becoming gusty to 25 knots
Monday afternoon and evening. Stratus returns Monday evening and
night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus, fog and drizzle /IFR-LIFR/ tonight
and Monday morning. Conditions lifting to MVFR-VFR Monday afternoon.
Stratus returns early Monday evening and night. Onshore winds 5 to
15 knots.

&&

.MARINE...
(Tonight through next Friday)
Issued at 441 PM PDT Sun Jul 13 2025

Localized hazardous marine conditions in the form of strong
northerly breezes and very rough seas will be present Monday and
Tuesday for the northern outer waters. Aside from that, a gentle
to moderate breeze with moderate to rough seas will prevail
through Thursday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 PM PDT
     Tuesday for Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Canepa

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