048
FXUS66 KMTR 101927
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1227 PM PDT Sun Aug 10 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1224 PM PDT Sun Aug 10 2025

 - Moderate HeatRisk continues through Monday for portions of the
   North, East and South Bay and interior Monterey and San Benito
   counties.

 - Elevated fire weather concerns persist given the warm and dry
   conditions, with breezy winds each afternoon and evening.

 - Pattern change on Tuesday brings cooler weather and coastal
   drizzle back to the forecast.

&&

.SHORT TERM...
Issued at 1224 PM PDT Sun Aug 10 2025
(This evening through Monday)

Satellite imagery shows stratus at the immediate coastline, with the
interior regions remaining clear for the day until the stratus
builds back into the inland valleys tonight. Smoke from the Gifford
Fire in San Luis Obispo County continues to waft into Monterey and
San Benito Counties, and high level smoke was also observed over the
Bay Area this morning. The smoke plume could continue to impact the
Central Coast through Monday. For further information on smoke
impacts to air quality, refer to forecasts issued by local air
quality management districts.

Today`s weather continues to be dominated by a ridge over the
northeastern Pacific that is building into the state. This ridge is
causing a hot and dry pattern that should continue into Monday. High
temperatures across the region today range from the 90s to near 103
in the inland valleys, the 70s to the mid 80s close to the Bays and
in the northern Salinas Valley, and the lower to middle 60s along
the Pacific coast. Similar temperatures are expected tomorrow with a
few degrees of cooling possible in the Bayside areas, but with
little relief for the warmest inland spots. Low temperatures on
Monday morning range from the middle 50s to lower 60s in the lower
elevations, up to the middle 60s to lower 70s in the higher
elevations. Breezy and gusty onshore winds should develop each
afternoon and evening with the strongest gusts reaching 30-35 mph
through favored gaps and passes, within favorably oriented valleys,
and across higher terrain.

The high temperatures today and Monday are causing moderate HeatRisk
across the inland portions of the Bay Area, Bayside regions of the
southeastern portions of San Mateo County and western Alameda
County, and portions of the inland Central Coast. This means that
there is a moderate risk for heat-related illnesses for populations
sensitive to heat, including children, the elderly, pregnant women,
people with certain chronic diseases, and people who work or live
outdoors without effective cooling or adequate hydration. Here are
some heat safety tips for people at risk for heat-related illnesses:

* 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 TERM...
Issued at 1224 PM PDT Sun Aug 10 2025
(Monday night through next Saturday)

A pattern change begins on Tuesday as the upper level ridge breaks
down, beginning a gradual cooling trend. A trough will then begin to
form over southwestern Canada and the Pacific Northwest on
Wednesday, reinforcing the cooling trend, building the marine
layer, and helping maintain the breezy and gusty onshore winds
each afternoon and evening through the middle of the upcoming work
week. The deeper marine layer will also enhance the chances for
coastal drizzle this upcoming week, potentially enough to see
accumulating drizzle in some areas. By Friday and continuing into
the upcoming weekend, temperatures should drop below the seasonal
averages, with high temperatures in the middle 70s to middle 80s
inland, the middle 60s to middle 70s along the Bays, and the lower
60s along the Pacific coast.

Beyond the 7 day forecast, ensemble model cluster analysis
supports a potential for a ridge to retrograde into California
from the Desert Southwest, and CPC outlooks lean towards
temperatures above the seasonal average and precipitation totals
below seasonal averages into the later part of August.

&&

.AVIATION...
(18Z TAFS)
Issued at 1118 AM PDT Sun Aug 10 2025

The marine layer remains near 1300 feet deep with a strong lower
level temperature inversion present under high pressure aloft. The
morning 12z Oakland upper air sounding mandatory pressure level
temps at 925 mb, 850 mb, 700 mb and 500 mb were 90th-95th percentile
for early-mid August. Mid to upper level thermal and height ridging
remains steady today, tonight and Monday however the NAM does
forecast near surface cooler air to undercut the thermal and height
ridge aloft by Monday morning. HREF IFR/MVFR probabilities shows
somewhat more of a leading edge of stratus reaching through the
Delta Monday morning. At the air/sea interface conditions are
favorable for stratus and fog, onshore winds ushering in stratus
and fog /MVFR-IFR-LIFR/ tonight and Monday morning. Patchy coastal
drizzle also developing in the cooler near surface air mass
tonight and Monday morning with gentle upsloping along the coastal
terrain. Stratus and fog then mixing out by late Monday morning,
increasingly VFR conditions redeveloping Monday afternoon.
Wildfire smoke aloft is also in the mix today, tonight and Monday
per recent HRRR smoke model forecasts. Smoke aloft likely reducing
slant range visibility especially near sunset and sunrise.

Vicinity of SFO...VFR has solidly returned now, there was an area
of stratus over the SF Bay, however that has mostly mixed out.
High confidence VFR forecast for the remainder of the day to early
to mid evening, stratus /MVFR/ returning 10z Monday morning. Stratus
mixes out by 17z Monday. Light northeast wind shifting to westerly
and increasing to 15 knots this afternoon to early evening. West
to northwest wind near 10 knots tonight and Monday morning, increasing
from the west 15 to 20 knots Monday afternoon.

SFO Bridge Approach...Reduced slant range visibility mainly near
sunset and sunrise due to wildfire smoke aloft. Otherwise similar
to SFO.

Monterey Bay Terminals...Diurnal mixing is decreasing the areal
stratus coverage late this morning. It`s a near high confidence
VFR forecast for the afternoon and early evening, then stratus,
fog and patchy drizzle /IFR-LIFR/ develop tonight and Monday
morning. Conditions improve to MVFR-VFR by late Monday morning,
with VFR Monday afternoon. Mainly west to northwest winds 5 to 15
knots.

&&

.MARINE...
(Today through Friday)
Issued at 906 AM PDT Sun Aug 10 2025

A gentle to moderate breeze and moderate seas will prevail through
Tuesday with diurnally driven afternoon sea breeze gusts up to 25
knots through the Delta. Winds increase and seas build Wednesday
with fresh to strong northwesterly breezes and rough seas on tap
for the outer waters and coastal jet regions.

&&

.FIRE WEATHER...
Issued at 906 AM PDT Sun Aug 10 2025

Not much change to the forecast for the next couple of days, with
hot and dry conditions persisting through Monday and breezy and
gusty onshore winds each afternoon and evening, both leading to
curing fuels and the possibility of rapidly spreading fires should
one start. Poor overnight humidity recoveries in the higher
terrain will contribute to the fire weather threats. As an upper
level ridge breaks down, the gusty afternoon winds will linger,
possible through the middle of the upcoming work week. However,
the cooling temperatures and deepening marine layer will help to
mitigate fire weather threats, and by the end of the work week a
trough should bring temperatures below seasonal averages across
the region.

DialH

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for SF Bay N
     of Bay Bridge.

     Small Craft Advisory from 1 PM to 11 PM PDT Monday for SF Bay N
     of Bay Bridge.

&&

$$

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

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