Cupertino, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

867
FXUS66 KMTR 240536
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
936 PM PST Sat Nov 23 2024

...New AVIATION...

.SYNOPSIS...
Issued at 810 PM PST Sat Nov 23 2024

Chances for scattered showers continues Sunday, with the North
Bay having the best chance for seeing between 0.25"-0.5" in the
afternoon and evening hours. More widespread rainfall is expected
on Monday as a disturbance moves onshore early Monday morning,
with highest rain totals expected farther south this time, from
the Santa Cruz mountains south into the Santa Lucias.

&&

.UPDATE...
Issued at 810 PM PST Sat Nov 23 2024

No update to the forecast necessary at this hour. A few weak
showers continue to linger across far southeast San Benito County,
but will eventually dissipate or move east out of our area over
the next couple of hours. Showers are expected tomorrow afternoon
across the North Bay with strongest activity likely to produce
between 0.25"-0.5", which if located properly, could cause
additional flooding concerns for areas hit hardest by the most recent
Atmospheric River.

Another round of more widespread rainfall is expected to begin
early Monday as a weak Atmospheric River sets up across the
southern portion of our forecast area, with the potential of 2"-4"
of additional rainfall possible from the Santa Cruz Mountains
south into the higher elevations of the Big Sur and the Santa
Lucias. Low lying areas and valleys will see less, possibly 1-2"
of rain between Monday and Wednesday.

&&

.SHORT TERM...
(This afternoon through Sunday)
Issued at 1144 AM PST Sat Nov 23 2024

The cold front has moved into southern California, leaving behind
a much drier, colder airmass. The precipitable water has dropped
from 1.08" to 0.64" and the 850 mb temp has dropped from 7.35C to
4.35C from 12Z yesterday to 12Z today. The short term convection
forecast is a bit of a mixed bag. As the sun peaks through and
allows the surface to warm, instability will rise. On the other
had, overall forcing is waning as a short wave trough moves toward
the Sierra. With mid-level lapse rates below 5 C/km and a
freezing level around 7,600 ft, any convection that forms will be
weak and shallow. Thunderstorms are very unlikely this afternoon.
Minor flooding impacts are still possible, but will require steady
training showers, as we saw over the East Bay in the late
morning.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 1144 AM PST Sat Nov 23 2024

A weaker trough will quickly move through Sunday, keeping light
rain chances in the forecast and bringing a brief pulse of
stronger southerly winds. Beyond Sunday, there is a lot of
uncertainty regarding the precipitation this week. A weak low
pressure system is likely to form just offshore somewhere between
Monterey Bay and San Francisco Bay. This low will generate a cold
front and SE winds will draw in moisture and moderate rain to the
warm sector. Where exactly this boundary sets up will have a
great influence on where the heaviest rain ends up. Our current
forecast keeps the heaviest rain over the Central Coast, but
that`s far from a guarantee. The ECMWF ensemble members show
anywhere from 0.25" to 2.0" at SFO, for example. Coastal mountains
may see up to 3 or 4 inches, but it`s unclear if that will be the
Santa Cruz mountains or the Santa Lucias. Regardless of where
exactly this system sets up, it will move south and allow
northerly flow to return by late Tuesday or Wednesday. The dry
weather should hold through Thanksgiving as a ridge begins to
build over the Eastern Pacific.

&&

.AVIATION...
(06Z TAFS)
Issued at 934 PM PST Sat Nov 23 2024

Mostly VFR conditions but some LIFR ceilings have developed near
KHAF. There is some uncertainty whether those ceilings will remain,
or will scatter out but models suggest near 12-15Z. KSTS currently
is experiencing MVFR/IFR conditions but confidence is low to
moderate on when clearing will occur but models suggest 16Z.
Otherwise, VFR through the TAF period for the remaining terminals.
S/SW winds will be relatively moderate with moments of westerly
winds going into the evening, then south/southwest winds overnight
into the morning.

Vicinity of SFO...VFR continues and is expected through the TAF
period. Winds have shifted back to a S/SW direction and is
relatively light but winds will rebuild by late Sunday
morning/early afternoon, accompanied by some light showers.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period for KMRY and
KSNS. Southerly winds return by early Sunday morning as light
vicinity showers start to move closer to the terminal.

&&

.MARINE...
(Tonight through next Friday)
Issued at 400 PM PST Sat Nov 23 2024

Winds and wave heights continue to decrease with occasional
scattered showers moving through the waters. Seas and winds
rebuild late tonight into early next week as another storm
approaches the region. Winds will initially be strongest north of
Point Reyes.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM to 3 PM PST Sunday for Pt Arena
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...SO
MARINE...SO

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