169
FXUS66 KMTR 160500
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1000 PM PDT Tue Jul 15 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
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.

&&

.UPDATE...
Issued at 839 PM PDT Tue Jul 15 2025

Satellite imagery shows stratus blanketing the coast, extending
into the Sonoma County valleys, the East Bay, and the Monterey Bay
region. No changes to the forecast at this time. Coastal drizzle
is still possible tonight through Wednesday morning.

DialH

&&

.SHORT TERM...
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.

&&

.LONG TERM...
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.

&&

.AVIATION...
(06Z TAFS)
Issued at 1000 PM PDT Tue Jul 15 2025

Satellite imagery shows coastal MVFR-IFR stratus flowing into the
Sonoma County valleys, the East Bay, and the Monterey Bay region and
Salinas Valley. Expect extensive stratus coverage through the night
with moderate confidence in stratus impacts at SJC and LVK. High
resolution models are not as bullish on impacts at SJC, will monitor
observed stratus coverage overnight. Stratus mixes out Wednesday
morning, except for the immediate coast where impacts continue
through the TAF period. Light winds continue through the night
before a breezy onshore flow returns Wednesday afternoon. Some of
the inland stratus returns on Wednesday evening, but the inland
terminals remain VFR through the end of the 24-hour TAF period.

Vicinity of SFO... Moderate confidence of stratus impacts at the
terminal beginning after midnight through Wednesday morning. High
resolution models show the terminal on the edge of the stratus deck,
while satellite observations appear to show stratus coming down the
East Bay hills. Both factors lower confidence on the timing of
stratus impacts. Stratus should mix out Wednesday morning with
breezy west-southwest winds developing Wednesday afternoon and
evening, with moderate confidence of gusts reaching 25 kt. Stratus
returns to SFO sometime Wednesday evening with moderate confidence
on timing.

SFO Bridge Approach... Slightly lower confidence in stratus impacts
tonight. Otherwise similar to SFO.

Monterey Bay Terminals... MVFR-IFR ceilings continue through the
night into Wednesday morning, when stratus retreats to the immediate
coast. Breezy onshore winds will develop Wednesday afternoon and
evening, with stratus returning to the terminals late Wednesday
afternoon.

&&

.MARINE...
(Tonight through next Monday)
Issued at 1000 PM PDT Tue Jul 15 2025

A gentle to moderate northwesterly breeze prevails through
Saturday. Moderate seas continue through the rest of the work week
with some rebuilding to become rough in the outer waters by
Saturday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...DialH
MARINE...DialH

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