736
FXUS66 KMTR 190808
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
108 AM PDT Tue Aug 19 2025

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

.KEY MESSAGES...
Updated at 245 PM PDT Mon Aug 18 2025

 - Warming trend into the weekend

 - Moderate HeatRisk for the interior Thursday-Saturday

 - See Heat Safety tips below

&&

.SHORT TERM...
Issued at 108 AM PDT Tue Aug 19 2025
(Today and tonight)

Satellite shows it`s clear except for a patch or two of coastal
stratus and fog. Except for patchy coastal stratus and fog, a sunny
day is forecast today. Forecast highs today will be within a few
degrees of normal mid August high temperatures, in the upper 60s
to lower 70s nearest the coast and bays and as warm to hot as the
mid 80s to lower 90s farthest inland.

&&

.LONG TERM...
Issued at 108 AM PDT Tue Aug 19 2025
(Wednesday through Monday)

A strong high pressure system near the Four Corners will place
our forecast area under increasing 500 mb high pressure with
increasing 925-500 mb thermal ridging through mid to late week.
Wind flow in the lower atmosphere will be temporarily northerly by
mid week and the marine layer will become compressed to near sea
level. Highs will warm to above normal for late August since 850
mb temps will be above the 90th percentile. Forecast highs in the
hottest spots farthest inland e.g. may approach 100F to 102F. In
general the 500 mb pattern across the Southwest U.S. and central/eastern
Pacific will be stationary to slightly retrogressive, keeping our
forecast area under the western portion of the Four Corners 500 mb
high pressure system.

Heat Safety Tips:

Heat is the number 1 weather related killer in the United States.
Follow these tips to protect yourself, your loved ones, and your
animals.

-Stay inside in an air conditioned environment between 10am and 7pm.
-Suspend unnecessary outdoor activities during moderate heat, but
 if you must be outdoors, take frequent breaks in the shade or AC
 and drink cool water.
-Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke!
Heat Stroke can be deadly if not treated immediately by a medical
professional. Call 911 if you suspect someone is suffering from Heat
Stroke.
-Wear a life jacket, swim near a lifeguard, and check conditions
before entering the water if going to a river or ocean to cool off.
Rivers and the ocean are extremely cold, and Cold Water Shock can
turn into paralysis and drowning if you are not careful.
-Use a cool and damp towel on your body if you do not have AC and
are feeling hot. Or, take a cool shower or bath.
-Do not leave kids or pets in a parked car.
-Ensure pets and livestock have access to shade and water.

&&

.AVIATION...
(06Z TAFS)
Issued at 957 PM PDT Mon Aug 18 2025

Satellite shows clear skies across the region with confidence
diminishing that widespread stratus will return tonight. Current
thinking is that the compressed marine layer and drier air mass will
make it harder for stratus to redevelop across the Bay Area tonight
given the current lack of cloud cover across the adjacent marine
zones. That being said, there is still a chance early tomorrow
morning for OAK and HAF to see some stratus, at least temporarily,
around sunrise. The only other sites with even a low end potential
for stratus are MRY and SNS. Winds generally stay onshore through
the TAF period with locally breezy winds to develop at SFO during
the afternoon/evening hours.

Vicinity of SFO...VFR. A drier air mass and compressed marine layer
will keep any stratus that is able to develop away from SFO tonight.
There is a low (~30%) chance that stratus will develop around
sunrise tomorrow morning within the 13Z-17Z as the most likely
timeframe. The more likely scenario is that patchy stratus will
develop in the vicinity of OAK and across portions of the SF Bay but
not impact the airport itself. Winds will remain gusty during the
afternoon and evening hours with gusts to around 25 knots expected.

SFO Bridge Approach...Patchy stratus may impact the bridge approach
early tomorrow morning with highest potential during the 13Z-18Z
timeframe. Otherwise, similar to SFO.

Monterey Bay Terminals...VFR. Confidence is decreasing that stratus
will develop at MRY and SNS tonight. LAMP, MOS, and HRRR guidance
have all trended downwards as to the amount of stratus coverage with
even the NAMNest (typically the most moist) model showing clear
skies over the Monterey Peninsula tonight. If any stratus does
develop it is not likely to occur until after 12Z and around
sunrise. There is a slightly higher chance for stratus to develop at
MRY than at SNS. Winds generally remain onshore through the TAF
period with winds between 10 to 15 knots expected during the day.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 957 PM PDT Mon Aug 18 2025

Winds increase midweek as the pressure gradient tightens with a
fresh to strong northwest breeze developing over the outer waters
and portions of the inner waters. Rough seas will build across the
outer waters mid to late week before seas subside and winds
diminish  over this weekend. Fresh to strong gusts are expected to
develop  across the San Francisco Bay each afternoon and evening.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT early this morning for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 9 AM PDT
     Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

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

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Kennedy
MARINE...Kennedy

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