929
FXUS66 KMTR 050040
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
529 PM PDT Fri Jul 4 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1209 PM PDT Fri Jul 4 2025

 - Elevated fire weather threat continues through Friday evening
   for the East Bay and Santa Cruz Mountains.

 - Northwest winds of 30 to 50 mph Friday afternoon and evening
   across gaps, passes, and some valleys.

 - Temperatures remain below seasonal averages into early next
   week, with a gradual warming trend towards the later part of
   next week.

&&

.SHORT TERM...
Issued at 1209 PM PDT Fri Jul 4 2025
(This evening through Saturday)

Satellite imagery reveals generally clear skies across the region
with the immediate coast south of Big Sur the last refuge of the
coastal stratus. Broad upper level troughing continues to dominate
the weather with temperatures near or below seasonal averages. Highs
will reach the middle 70s to the lower 80s in the inland valleys, to
the lower 90s in the southern reaches of Monterey and San Benito
County, the middle 60s to lower 70s near the Bays, and the upper 50s
to the middle 60s at the Pacific coast. Breezy and gusty afternoon
winds will develop across the region, with gusts reaching 30 to 50
mph through the gaps and passes, along the coast, and through the
Salinas Valley.

As the evening goes on, patchy low clouds could develop along the
coast and on the west side of the Berkeley-San Leandro Hills, but
most regions should remain clear through early Saturday morning. The
City, in particular, could very well remain clear throughout its
July 4th celebration tonight. By 9 PM, the temperatures should cool
to the middle 50s to lower 60s for most of the region, with the
higher elevations remaining significantly warmer (up to the middle
70s). As a reminder, be careful when celebrating the holiday,
especially if your plans involve fireworks or open flames (including
grilling). With the gusty winds and dry conditions inland,
particularly the higher elevations of the East Bay and the Santa
Cruz range, elevated fire weather threats continue into the evening.
One less spark, one less fire!

Low temperatures on Saturday morning drop into the upper 40s to the
middle 50s for the lower elevations and up to the lower 60s for the
highest peaks. A few degrees of warming are possible on Saturday as
the upper level trough erodes, but the overall pattern remains
similar.

&&

.LONG TERM...
Issued at 1209 PM PDT Fri Jul 4 2025
(Saturday night through next Thursday)

Sunday should see a cutoff low splitting from the remnants of the
trough and setting up just off our coastline, leaving temperatures
cooler than the seasonal averages into the early part of next week.
The marine layer will also expand, allowing for further inland
stratus intrusions, while breezy onshore flow continues with a
southerly component, although the wind gusts are not expected to be
as strong as those seen yesterday and today.

The low pressure system weakens and meanders northward late Monday
into Tuesday, allowing an upper level ridge over the Desert
Southwest to build and a warming trend to start. This event looks to
be similar to the previous warm periods we`ve had, where the coastal
regions remain relatively cool while the interior regions heat up.
By the end of the upcoming work week, temperatures near 100 are
possible in the warmest spots, leading to areas of Moderate
HeatRisk, corresponding to a moderate risk for heat-related
illnesses for populations sensitive to heat. Some uncertainty still
remains regarding the evolution of the upper level low and the
evolution of the ridge, so stay tuned as the long range heat
potential is refined through the next few days.

&&

.AVIATION...
(00Z TAFS)
Issued at 529 PM PDT Fri Jul 4 2025

It`s VFR at all terminals and visible satellite imagery shows a
clear sky, remarkable timing for the July 4th holiday. The 4.4 mb
SFO-SAC onshore pressure gradient and wind predominate while the
northerly gradient ACV-SFO is 2.6 mb. The marine layer depth i.e.
from sea level to the lower level temperature inversion varies from
1200 to 1800 feet over the Bay Area, to a somewhat more compressed
1000 feet depth at the Point Sur profiler (where thermal ridging
aloft is stronger). As mentioned, it`s clear, and conditions
could`ve easily supported stratus and fog early this evening.
However there`s currently sufficient mixing with drier air aloft,
there has been some weakening of the marine layer temp inversion
due to cool air advection and perhaps there`s an early hint of
tonight/Saturday morning`s continental air mass intrusion from the
north. Model forecasts are currently over-forecasting stratus and
fog and hold onto this forecast tonight and Saturday morning, thus
it`s likely that stratus/fog /IFR-LIFR/ will form later tonight and
Saturday morning under nocturnal radiative cooling to space. Stratus
and fog /LIFR-IFR/ will mix out to coastline Saturday otherwise VFR
is forecast. Onshore winds prevail during the 00z TAF cycle.

Vicinity of SFO...VFR. West wind gusts to 35 knots until 05z this
evening, wind easing thereafter through late tonight and Saturday
morning. West wind increasing to 17 gusts to 25 knots Saturday
afternoon and early evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...24 hour temps/dewpoint temps trends are
warmer/drier, supporting moderate to high confidence VFR forecast
for early to mid evening. With nocturnal radiative cooling and
more focused lower level cool air advection tonight and Saturday
morning, this supports redevelopment of stratus and fog /IFR-LIFR/,
timing is mainly after midnight to Saturday morning. Then diurnal
mixing will lift IFR-LIFR to MVFR-VFR by late Saturday morning and
early afternoon. Mainly onshore winds 5 to 15 knots.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 436 PM PDT Fri Jul 4 2025

Fresh to strong northwesterly breezes and moderate seas will
continue through the weekend with winds easing into early next
week.  Gale force gusts will be likely near Pt. Sur through Friday
night  and again Saturday afternoon. Winds look to increase and
significant  wave heights look to build beginning late week.

&&

.FIRE WEATHER...
Issued at 3 AM PDT Thu Jul 4 2025

Breezy onshore flow persist overnight with gusts 30-50 mph.
Thankfully, most areas are seeing some marine influence with
at least moderate humidity recovery. Winds may ease slightly
before sunrise. Onshore flow will ramp back up this afternoon as
the Central Valleys heats up. RH values will drop, but be tempered
by onshore flow keeping them from really bottoming out. That being
said, strong winds for inland gaps/passes and moderate RH will
lead to elevated or near critical fire weather concerns. Grasses
and finer fuels remain cured and available, and given the
potential for new ignitions due to the holiday weekend, an
increase in initial attack type activity should be expected by
local fire personnel. Less favorable burn conditions are
anticipated this weekend as the marine layer deepens and invades
parts of the area. However, far interior portions of the Bay Area
and Central Coast, as well as regions above 1500-2000 feet may
still remain within an airmass characterized by near-critical
humidity and winds where there may remain some potential for fire
spread/growth.

MM/Bain

&&

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

     Small Craft Advisory from 3 PM to 9 PM PDT Saturday for SF Bay N
     of Bay Bridge.

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

     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.

     Small Craft Advisory until 9 AM PDT Saturday for Pt Reyes to
     Pigeon Pt 0-10 nm.

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

     Small Craft Advisory from 9 AM Saturday to 3 AM PDT Sunday for
     Pigeon Pt to Pt Pinos 0-10 nm.

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

&&

$$

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

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