335
FXUS66 KMTR 290834
AFDMTR

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

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.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

&&

.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...
(06Z TAFS)
Issued at 916 PM PDT Thu Aug 28 2025

Sharp marine layer expansion this evening which ideally would lead
to slightly higher CIGs and potentially coastal DZ overnight
tonight and into Friday morning. Later arrival for stratus than
previously anticipated, but confidence is still high that we will
see MVFR/IFR cigs across most terminals before sunrise Friday. A
deeper marine layer will also likely lead to a later clearing time
for some coastal and Bay Area terminals. Otherwise no surprises
expected regarding winds through Friday.

Vicinity of SFO...VFR going into the nighttime hours with moderate
confidence in timing of MVFR cigs Friday morning. Confidence is
higher that the terminal will see cigs to come extent around
sunrise Friday, but the time of arrival is less certain.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Later stratus arrival than previously
anticipated, but confidence is still high in MVFR cigs overnight
and into mid morning Friday. Coastal DZ also appears likely as the
marine layer deepens.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 239 PM PDT Thu Aug 28 2025

Light winds and seas continue across the coastal waters through
the end of the week. Increasing wave heights and fresh to strong
gusts develop through the weekend, bringing hazardous conditions
across the coastal waters into next 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 0-10 nm-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 PM this evening to 3 AM PDT Sunday
     for Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-
     10 nm.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Behringer
MARINE...Behringer

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