074
FXUS66 KMTR 291607
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
907 AM PDT Fri Aug 29 2025

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 133 AM PDT Fri Aug 29 2025

 - Temperatures near seasonal averages today, warming for the
   weekend through the middle of next week

 - Elevated fire weather concerns across the interior mountains
   this weekend with low RH and moderate onshore winds in the
   afternoons

 - Hazardous coastal conditions Saturday through Tuesday due to
   long period southerly swell

&&

.UPDATE...
Issued at 907 AM PDT Fri Aug 29 2025

While the marine layer remains between 1,200-1,500 feet in depth
this morning, very dry conditions prevail above these elevations.
Thus, expecting higher elevations across the region to remain dry
throughout the forecast period has high pressure builds in from the
west. Have made adjustments to the hourly RH grids for this morning
to better reflect these dry conditions aloft.

RGass

&&

.SHORT TERM...
Issued at 133 AM PDT Fri Aug 29 2025
(Today and tonight)

Satellite imagery shows the stratus decks generally remaining
offshore, with patchy stratus developing in the Berkeley-San Leandro
Hills and around the Monterey Bay region. We are still expecting
inland stratus to develop, although a compressing marine layer
will limit the extent of the stratus deck, with lows dropping into
the 50s across the lower elevations, and the 60s in the higher
elevations. Temperatures remain close to the seasonal averages
today, with high temperatures ranging from the 80s to the lower
90s inland, to the 70s and lower 80s along the Bays, and the lower
to middle 60s along the Pacific coast. Breezy onshore winds will
develop in the afternoon, with the strongest gusts of 25 to 30 mph
occurring through favored gaps and passes, within the Salinas
Valley, and along the coast.

&&

.LONG TERM...
Issued at 133 AM PDT Fri Aug 29 2025
(Saturday through Thursday)

An upper level ridge develops over the West Coast through the
weekend, leading to a warming trend across the region. Moderate
HeatRisk develops in the interior regions as high temperatures shoot
up into the middle 80s to the 90s, with the warmest spots reaching
the triple digits. This level of heat will bring a risk of heat-
related illnesses to vulnerable populations, including children, the
elderly, pregnant women, and people who are working or living
outdoors without adequate shelter or hydration. Near the coasts, a
compressed marine layer should retain the ability to keep
temperatures from rising dramatically, but areas that will lose the
marine layer influence, including much of the Bay Area, could see
temperatures jump 5 to 10 degrees. The extreme heat will also
contribute to some elevated fire weather conditions across the
interior mountains. More information is available in the FIRE
WEATHER section.

Some tips to avoid heat-related illnesses include:

* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.

Long-period south-southwest swell originating from Tropical Storm
Juliette will impact the coast Saturday through Tuesday, creating an
elevated risk for sneaker waves, rip currents, and rough surf. The
potential exposure to the dangers will be enhanced by the Labor Day
holiday weekend and the warm conditions in the interior.

From the previous forecaster: Models struggle to show anything truly
breaking the ridge pattern through the next work week, and even hint
at additional warming in the mid week and a plateauing of
temperatures into the next weekend. This suggests some potential for
prolonged heat affecting the area, and only modest cooling after the
ridge pattern slowly resolves well into the long-term forecast. This
will be something to keep track of as the forecast develops.

&&

.AVIATION...
(12Z TAFS)
Issued at 445 AM PDT Fri Aug 29 2025

Stratus has begun to build up along the coast and is expected to
result in IFR/MVFR ceilings for most terminals between now and
late morning. Stratus is expected to lift and retreat to our outer
waters once again leaving VFR conditions for the afternoon
through much of the overnight hours into early Saturday morning.

Vicinity of SFO...Low stratus is beginning to envelope the Bay
Area terminal as of this issuance (5am PDT). IFR/MVFR ceilings are
expected to linger in vicinity of the terminals through late
morning, then VFR for the remainder of the day into the early
morning hours of Saturday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...An Otter Eddy has filled in over Monterey
Bay bringing IFR ceilings. There may be some breaks in the
ceilings through late morning, but are expected to prevail until
clearing out entirely by early afternoon. Expect another evening
of VFR into the early hours of Saturday morning before stratus
redevelops during the overnight hours.

&&

.MARINE...
(Today through Wednesday)
Issued at 907 AM PDT Fri Aug 29 2025

Expect increasing wave heights through the weekend with fresh to
strong wind gusts developing Friday afternoon and lasting through
the holiday weekend. The gusty winds and choppy seas will create
hazardous conditions across our coastal waters through the weekend
into the beginning of the next work week.

&&

.FIRE WEATHER...
Issued at 133 AM PDT Fri Aug 29 2025

A warming and drying trend combined with breezy afternoon winds will
result in elevated fire weather conditions across the interior
mountains. Daytime conditions will be hot and dry with relative
humidity values reaching the 10-20% range in the higher elevations.
With a compressing marine layer coupled with a strong inversion, the
thermal belts will activate, leading to poor overnight humidity
recoveries and mild overnight lows, both of which will provide
little to no relief for the higher elevations. Breezy onshore winds
will develop each afternoon and evening with gusts reaching 20-30
mph through favored gaps and passes, with a particular focus on the
East Bay interior. ERC forecasts are showing an increase in the risk
of large fires through the next several days across the interior.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Sunday
     for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-
     10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

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

     Small Craft Advisory from 9 PM this evening to 3 AM PDT Sunday
     for Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...Murdock

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