-- Discussion containing changed information from previous version are highlighted. --
679
FXUS66 KMTR 152111
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
211 PM PDT Tue Jul 15 2025

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

.KEY MESSAGES...
-- Changed Discussion --
Updated at 209 PM PDT Tue Jul 15 2025

 - Below seasonal temperatures continue through Thursday before a
   slight warming trend begins Friday into the weekend.

 - Localized elevated fire weather threat continues across the
   higher elevations.
-- End Changed Discussion --

&&

.SHORT TERM...
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Issued at 209 PM PDT Tue Jul 15 2025
(This evening through Wednesday)

Widespread stratus to return again tonight as the marine layer holds
steady around 2000 ft in part thanks to persistent upper level
troughing over the West Coast. Quite a few coastal sites (Half Moon
Bay, Laguna Seca, Bodega Bay, Point Reyes) reported at least a
hundredth of an inch of drizzle this morning. Coastal areas can
expect to see patchy drizzle (similar to today) and fog again
tomorrow morning as low level clouds move in overnight.

In terms of temperatures, today marked the beginning of a slight
cooling trend with seasonal to below normal temperatures to continue
through the end of this week. Temperatures across the interior are
forecast to be between 5 to 10 degrees below normal tomorrow with
highs largely in the 70s to 80s across the interior. Far interior
East Bay (Byron area) and far interior Central Coast (Fort Hunter
Liggett, Bradley)continue to be the two hot spot regions with highs
peaking in the upper 80s to possibly low 90s. Generally the below
normal temperatures and deeper marine layer are helping to mitigate
fire weather concerns for the lower elevations, but for areas above
the marine layer (~2000+ ft in elevation) dry conditions continue
with only minor improvements in overnight humidity
recoveries/daytime humidity retention. Winds remain light and
onshore through the period with the exception of mountain ridgetops,
mountain gaps/passes, and areas where terrain funneling is able to
occur (valleys). Diurnally breezy conditions are expected across
these areas with gusts to around 25 mph anticipated. The breeziest
conditions will be in the vicinity of the Altamont Pass where gusts
will peak closer to 30 to 35 mph.
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&&

.LONG TERM...
-- Changed Discussion --
Issued at 209 PM PDT Tue Jul 15 2025
(Wednesday night through next Monday)

Not too many changes in the Long Term forecast, weak upper level
troughing will generally keep temperatures below normal through
Thursday with highs in the upper 70s to mid 80s. A slight warming
trend begins Friday into the weekend as our persistent upper level
trough weakens and is forced northward towards the PNW by
redeveloping high pressure over the Pacific Ocean. As the trough is
pushed northward, high pressure located over the Four Corners region
will expand and push into the Bay Area and Central Coast. This will
result in our marine layer compressing (limiting the inward extent
of stratus overnight) and allow temperatures to warm more across the
interior. This will bring temperatures closer to normal across the
interior with highs in the upper 70s to 80s. For far interior
locations and locations above the marine layer (~2000 ft),
temperatures will be seasonal to slightly above normal in the mid to
upper 90s. HeatRisk concerns are minor through the end of the
forecast period with good overnight cooling into the mid 50s to low
60s expected. Fire weather concerns remain minimal across the lower
elevations but remain locally elevated across the higher elevations
above the marine layer. Conditions dry out above 2000-2500 ft Friday
through the weekend with overnight humidity recoveries between 20-
35% and daytime humidity retention between 15-25%. Winds remain
onshore but are expected to be diurnally breezy through mountain
gaps/passes, along ridgetops, and across areas where terrain
funneling is likely (valleys). Anyone visiting the mountains should
keep in mind the saying, one less spark, one less wildfire.

Temperatures start to cool again Monday, returning to seasonal to
slightly  below normal temperatures, as upper level high pressure
weakens and a cut-off low in the Pacific Ocean tries to strengthen
and push towards the West Coast. Hopefully Bay Area/Central Coast
residents are not fully opposed to the relatively mild summer that
we have had so far as the CPC indicates temperatures will lean below
normal through the end of July.
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&&

.AVIATION...
(18Z TAFS)
Issued at 1030 AM PDT Tue Jul 15 2025

Currently a mixed bag of IFR-VFR at the terminals. An upper-level
shortwave trough helped deepen the marine layer to 2,200 feet and
produce coastal drizzle. A second upper-level shortwave trough will
approach the region towards the end of the TAF period, so all in
all, a persistence forecast is on tap.

Vicinity of SFO...Currently VFR with northerly flow. Westerly flow
will return once the sea breeze kicks in this afternoon. High
confidence (up to 80%) in an MVFR ceiling developing tonight.

SFO Bridge Approach...Low stratus clouds will begin to filter in
through the Golden Gate Gap late this afternoon and linger through
tomorrow morning.

Monterey Bay Terminals...Currently IFR with southwesterly flow at
MRY and MVFR with northwesterly flow at SNS. High confidence in IFR
ceilings returning to both terminals tonight.

&&

.MARINE...
(Today through Sunday)
Issued at 925 AM PDT Tue Jul 15 2025

Localized hazardous marine conditions in the form of strong
northerly breezes and very rough seas will continue through this
afternoon for the northern outer waters. Wednesday through
Saturday will bring widespread gentle to moderate breezes and
moderate seas.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Sarment
MARINE...Sarment

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