Sunnyvale, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

337
FXUS66 KMTR 130201
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
701 PM PDT Thu Jun 12 2025

...New AVIATION...

.SYNOPSIS...
Issued at 139 PM PDT Thu Jun 12 2025

Daily coastal stratus, breezy afternoon onshore winds, and
interior highs in the 70s to 80s and low 90s across the far
interior continue through this weekend. Dry conditions persist for
elevated terrain above the marine layer leading to some fire
concerns as grasses and smaller plants continue to cure.

&&

.SHORT TERM...
(This evening through Friday)
Issued at 139 PM PDT Thu Jun 12 2025

The steady trend of coastal stratus in the morning, clearing for a
few hours in the afternoon, and returning again during the evening
continues Friday. The marine layer remains around 2000 ft and is
expected to stay at that depth with no major changes to our zonal
synoptic pattern in the short term. Areal stratus coverage has
dissipated over the past few days with stratus coverage expected to
continue diminishing across the North Bay and interior Bay Area
tonight. The highest likelihood is stratus persisting along the
coastline and into portions of the SF Bay shoreline. High
temperatures are set to be in the 70s to mid 80s on Friday with the
far interior Central Coast peaking in the low to mid 90s.

Gusty onshore winds return this afternoon and again tomorrow
afternoon with the strongest gusts expected across mountain
gaps/passes, across the elevated terrain, and along portions of the
coastline. Highest confidence is in gusts peaking between 30 to 35
mph but stronger gusts may develop along the highest peaks and in
areas where funneling is favored (such as the Altamont Pass). With
that in mind, an increased risk of grass fires exists across the
higher elevations above the current marine layer depth (~2000 ft).
This is particularly true for the North Bay Interior Mountains,
East/South Bay Hills, and interior Monterey/San Benito Counties.
Across the North Bay Interior Mountains and East/South Bay Hills,
daytime humidity values are dropping into the 25-35% range. Daytime
humidity values drop further in the interior Central Coast with
values dropping into the 12-20% range. Larger fuels are still
decently moist but are in the process of drying out. In the past few
days the Dino Fire (Santa Clara) and Little Fire (San Benito) have
been observed in dry, flashy small (grass) fuels and serve as a
reminder that summer is here. For those living in the higher
elevations, take precautions if utilizing an outdoors stove or
campfire and follow all local guidance.

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 139 PM PDT Thu Jun 12 2025

The general pattern of more zonal flow and ridging to our east over
the Intermountain West will help to keep our overall forecast steady
through this weekend. High temperatures will generally stay in the
upper 70s to mid 80s across the interior Bay Area and in the 90s
across the interior Central Coast. Closer to the coastline
temperatures will be cooler in the upper 50s to mid 60s. The marine
layer looks to hold steady, if possibly compress slightly, around
2000 ft with daily coastal stratus to continue through this weekend.
The pattern becomes a bit more uncertain Monday into early next week
when a weak shortwave trough moves looks to move through the Bay
Area. This trough is likely to allow the marine layer to deepen and
for stratus to spread further into the Bay Area and Central Coast.
This will help to keep temperatures cooler on Monday (highs in the
upper 70s to low 80s across the interior) before a slight warming
trend begins Tuesday. Interior temperatures will rise into the mid
to upper 80s on Tuesday and mid 80s to low 90s on Wednesday. The
warmest portions of the interior Central Coast will reach the mid
90s to low 100s on Wednesday. Gusty winds across the elevated
terrain, gaps/passes, and along the coast will continue into next
week along with drier daytime conditions across the interior. Modest
improvements in daytime humidity values are expected across the
interior Bay Area over the weekend but dry conditions across
interior Monterey and San Benito Counties will persist into next
week.

&&

.AVIATION...
(00Z TAFS)
Issued at 700 PM PDT Thu Jun 12 2025

Vicinity of SFO...Visuals around SFO this evening show clouds
generally confined to the western side of the peninsula, hovering
around San Bruno. Expect stratus to creep back in throughout the
rest of the evening bringing another night of MVFR cigs. Clearing
should begins mid to late morning, with VFR skies expected by the
afternoon. In terms of Friday night into Saturday, the signal for
stratus looks to come in around or shortly after 6Z. Finally,
gusty westerly winds are forecast to linger through the evening,
before falling to 10-15kt overnight. Onshore, mainly westerly
winds are expected to pick up again tomorrow afternoon.

SFO Bridge Approach...Satellite imagery and webcams show the SFO
approach with clear skies as stratus hugs western side of San
Francisco County. Model guidance suggests that stratus fills in from
both the east and west which may blanket portions of the southern
portion of the Bay later tonight. Timing shows that CIGS could start
creeping in as early as 6-9Z with a slightly stronger single for
somewhere between 11-14Z. Confidence is low on timing as the marine
layer looks to be more compressed.

Monterey Bay Terminals...Stratus continues to linger around the KMRY
this afternoon with stratus covering up to Marina. Expect stratus to
fill in tonight, leading to another MVFR to IFR cigs. Expect skies
to clear mid to late morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 1032 AM PDT Thu Jun 12 2025

Fresh to strong northwesterly breezes, near gale force gusts, and
moderate to rough seas will prevail through Monday. Expect gale
force gusts to develop near the coastal jet regions of Point Reyes
and Point Sur during the afternoon and evening hours of today and
again Friday.

&&

.FIRE WEATHER...
Issued at 252 AM PDT Wed Jun 12 2025

Areas not being reached by the marine layer continue to see dry
conditions. Higher elevations, particularly in the Santa Lucias
and in the Gabilan range, continue to see poor humidity retentions
and recoveries. In fact, some locations are hitting single digit
and lower teens for RH values. A few locations in the interior
North Bay are seeing breezy north to northeast winds and these
winds look to last into the morning which will increase drying in
these areas. Winds will remain breezy each afternoon/evening
through the Delta, and any inland gap or pass. The combination of
dry fine fuels (grasses), lower RH, breezy winds with gusts in the
20-40 mph will elevate fire weather concerns.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay.

     Small Craft Advisory from 9 AM to 9 PM PDT Friday for Mry Bay.

     Gale Warning until 9 PM PDT this evening for Pt Arena to Pt
     Reyes 0-10 nm.

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

     Gale Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras
     Blancas 0-10 nm.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...KR
MARINE...Sarment

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