880
FXUS66 KMTR 031139
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
439 AM PDT Thu Jul 3 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 232 AM PDT Thu Jul 3 2025

 - Elevated Fire Weather concerns Thursday afternoon and evening
   for the East Bay and Santa Cruz Mts.

 - Breezy northwest winds Thursday afternoon and evening.

 - Night and morning low clouds clearing to the coast each
   afternoon remains.

 - Near normal temperatures with a slightly below normal
   temperatures Thu & Fri.

&&

.SHORT TERM...
Issued at 300 AM PDT Thu Jul 3 2025 (Today and tonight)

Overnight satellite fog product shows a slightly different set up
early Thursday morning compare to the last few nights. While we
still have some marine layer clouds extending into the Salinas
Valley, northern areas are seeing much less in the way of low
clouds. A pocket of drier air near the surface, stronger N-S
gradient, and passing high level clouds are all likely
contributing to less clouds. Latest hi-res capture this rather
well so portions of the North Bay, East Bay, and Bay Shoreline
will likely see the sunrise unlike the last few mornings. Coastal
San Mateo southward to Big Sur, including Monterey Bay region,
will be cloudy. Decided to remove drizzle from the forecast as
well based over observation and lastest model guidance.

The bigger story for Thursday will be the changing longwave
pattern overhead leading to gusty onshore winds. An upper level
shortwave trough currently upstream will sweep through the state
this afternoon. As such onshore flow will ramp up through the day
and peak close to 5 mb for SFO-SAC. That translates to gusty winds
25-40 mph for the coast, mts, gaps/passes. Could even see some
isolate gusts up to 50 mph for the East Bay Hills. The passing
trough will also usher in some drier air leading to fire weather
concerns. See Fire Section below for details.

If one happens to look at satellite you`ll notice the Madre Fire
currently burning in SLO. Given transport flow smoke from this
fire is currently not expected to impact the forecast area.

&&

.LONG TERM...
Issued at 315 AM PDT Thu Jul 3 2025
(Friday through Wednesday)

By Friday, the shortwave trough will have exited to the east as
broad troughing will remain over the West. Therefore, a cloudy
start to the 4th of July is expected with some afternoon sunshine.
Temperatures will be mild, but seasonably cool for early July.
What about clouds impacting evening activities? Definitely
possible as the marine layer begin to move inland. Greatest
impacts will be for the immediate coast, Monterey Bay region, and
through the Golden Gate.

For the upcoming holiday weekend - seasonably cool with
night/morning clouds and inland afternoon sunshine. Early next
becomes a little more uncertain as guidance develops another cut-
off low off the Bay Area coast. Upper lows are always tricky with
regards to marine layer development and possible precip. This low
looks to be dry, but we`ll keep an eye on it. By Wednesday this
feature drifts north as a Four Corner high builds westward. The
building ridge will kick off a warm trend.

&&

.AVIATION...
(12Z TAFS)
Issued at 439 AM PDT Thu Jul 3 2025

Stratus and patchy fog /IFR-LIFR/ are moving inland on onshore
winds. High clouds will also move through to the east with a 500
mb trough. Stratus and fog mix out back near the coastline during
the afternoon with a return of stratus and fog /IFR-LIFR/ tonight
and Friday morning.

Vicinity of SFO...VFR prevails today, stratus /MVFR/ returns early
Friday 10z. Light and variable wind this morning, becoming west
and increasing to 20 to 30 knots this afternoon and early evening.
West wind easing to 5 to 15 knots tonight and Friday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus and patchy fog /IFR-LIFR/ lifting
to MVFR-VFR by late morning. Stratus /IFR/ returns tonight and
Thursday morning. Mainly onshore winds 5 to 15 knots.

&&

.MARINE...
(Today through Tuesday)
Issued at 424 AM PDT Thu Jul 3 2025

Gusty northwesterly winds and rough seas will continue through
late today. Gale force gusts will be likely across northern waters
through today. Winds easing by early next week. A low-amplitude
long period southerly swell will arrive today and persist through
Friday.

&&

.FIRE WEATHER...
Issued at 315 AM PDT Thu Jul 3 2025

No real change from previous thinking. Increasing winds this
afternoon and lower humidity will create near critical fire
weatherconditions. Areas of greatest concern continue to be the
East Bay Hills, Eastern Santa Clara Hills, and Santa Cruz
mountains. Winds will be gusts 25-40 mph with isolated gusts up to
50 mph (Think Altamont Pass). The current wind forecast and state
of the fuels will allow for a spike in the Burn Index for the
Diablo/Santa Cruz region. Predicted values will exceed the 97
percentile. Simply put, be one less spark, especially with the
holiday and potential firework impacts.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Mry Bay-SF Bay N of Bay Bridge.

     Small Craft Advisory from 3 PM to 9 PM PDT Friday for Mry Bay-SF
     Bay N of Bay Bridge.

     Gale Warning until 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10
     nm.

     Small Craft Advisory until 3 PM PDT Friday for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Small Craft Advisory from 9 AM this morning to 9 PM PDT this
     evening for Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory from 9 AM to 9 PM PDT Friday for Pigeon Pt
     to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 PM PDT this afternoon for Pt Pinos
     to Pt Piedras Blancas 0-10 nm.

     Gale Warning from 3 PM this afternoon to 9 PM PDT Friday for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

     Gale Warning until 9 PM PDT this evening for Pt Arena to Pt
     Reyes 10-60 NM.

     Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt
     Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Canepa
MARINE...Canepa

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