Cupertino, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

808
FXUS66 KMTR 150812
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
112 AM PDT Wed Oct 15 2025

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

.KEY MESSAGES...
Updated at 106 AM PDT Wed Oct 15 2025

 - Warming and drying trend kicks off today and lasts through
   Saturday

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

 - Unsettled weather possibly returns Sunday

&&

.SHORT TERM...
Issued at 106 AM PDT Wed Oct 15 2025
(Today and tonight)

Isolated rain shower activity will continue to wane through the
morning with dry conditions expected by daybreak or shortly there
after. A warming and drying trend kicks off today as upper-level
shortwave ridging nudges the mid-to-upper level low east. It
certainly won`t feel like it though with widespread temperatures
of 10-20 degrees below normal. Patchy frost will be possible
tonight for far interior portions of Monterey and San Benito
Counties. Frost or not, it is going to be cold and proper
precautions should be taken to protect people, pets, and plants.

&&

.LONG TERM...
Issued at 106 AM PDT Wed Oct 15 2025
(Thursday through Tuesday)

By tomorrow, surface high pressure will build into the Pacific
Northwest which will create a northerly (drying) gradient across the
state. Surface high pressure will continue to build into the Great
Basin Friday into Saturday with a coastal trough developing off the
coast of California. This pattern will facilitate textbook offshore
flow as pressure flows from high to low and winds follow suit. Both
of these patterns will be no cause for concern fire weather (or
other) wise with the recent widespread wetting rainfall putting a
damper, but not quite an end, to fire weather season. Global
ensemble clusters are in agreement that a cut-off low will get
pinched off from leftover troughing from the beginning of the
forecast period with heights falling by Sunday. What that means
for us is still up in the air (literally). A cut-off low is
uncertain by nature due to it`s independence from the jet stream,
but the big question here is what kind of flow regime are we going
to be in? Heights rising? Heights falling? Split flow where it`s
some combination of both? Zonal? It`s difficult to say, but either
way it does not look to be impactful no matter the solution. The
deterministic ECMWF and GFS both have an upper-level longwave
trough moving into the region Sunday. The ECMWF has a quicker
solution while the GFS has a slower, deeper solution that would be
able to absorb the cut-off low back into the jet stream. As of
now the forecast is dry, but there is still a significant amount
of spread amongst total precipitation ensembles. For now, I would
expect an increase in cloud cover and winds over the weekend.
Unfortunately this uncertainty will impact the confidence in the
forecast at the beginning of next week; thus, it is uncertain on
if heights will rebuild or if the aforementioned trough will
continue to dig.

&&

.AVIATION...
(06Z TAFS)
Issued at 945 PM PDT Tue Oct 14 2025

VFR-MVFR with widely scattered showers and patchy fog and low
clouds /LIFR-IFR/ tonight and Wednesday morning. Dry weather and
VFR Wednesday.

Vicinity of SFO...VFR-MVFR. Vicinity showers tonight otherwise
drier conditions Wednesday. West wind 5 to 10 knots becoming light
and variable tonight and Wednesday morning. West to northwest
wind 5 to 10 knots late Wednesday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR-MVFR. Mainly onshore winds 5 to 10
knots becoming southeast winds 5 to 10 knots tonight and Wednesday
morning. Onshore winds near 10 knots redeveloping Wednesday
afternoon.

&&

.MARINE...
(Tonight through next Monday)
Issued at 852 PM PDT Tue Oct 14 2025

Low pressure and cold air aloft will result in a few additional
showers across the waters through sunset. Otherwise dry northerly
winds will return to the waters tonight through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa

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