410
FXUS66 KMTR 111159
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
459 AM PDT Wed Sep 11 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 120 AM PDT Wed Sep 11 2024

An upper level trough moving into the Pacific Northwest today will
bring breezy winds to the region that will continue into Thursday.
Slightly warmer for Friday, near seasonal averages. Then a second
trough will begin to impact the region bringing chances of
precipitation at times through next week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 120 AM PDT Wed Sep 11 2024

A deep upper level trough is currently off of the Pacific Northwest
coast and is progressing southeastward and will move into the
Pacific Northwest by this evening. This will result in breezy
onshore winds late this morning and through the evening hours.
Widespread gusts of 30 mph are expected with gusts of 50+ mph
especially in the gaps, passes, and other favorable spots, namely
the Altamont Pass and the Salinas Valley. However, these speeds fall
short of needing a Wind Advisory but conditions will be monitored
closely.

A reminder from the previous forecaster...

Actions to take:

-Store or secure loose items such as patio furniture, sports
equipment, trampolines, and trash cans.

-Use caution when driving, especially high-profile vehicles.

-Have a plan in case of a power outage.

While the overall fire threat is on a downward trend due to lower
temperatures and higher relative humidities, fuels still remain
critically dry with large fires possible. Therefore, any fire that
starts will have no problem spreading and the strong winds will only
make matters worse. As always, it is imperative to remain vigilant
when it comes to exercising fire safety.

Actions to take:

-Properly discard cigarettes.

-Keep vehicles off of dry grass.

-Avoid activities with open flames or sparks.

-Avoid power equipment that creates sparks.

-Obey burn bans.

Tonight, winds diminish late this evening as the trough axis moves
inland and high pressure builds off of the West Coast. Expecting
northwest flow to remain breezy over the ocean with less widespread
cloud cover overnight. Any clouds will favor the northwest facing
terrain as a result.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 120 AM PDT Wed Sep 11 2024

As the aforementioned trough shifts further inland, weak offshore
flow may develop over the Interior North Bay Mountains and East Bay
Hills on Thursday and into Friday morning. However, strong winds
that would reach Red Flag criteria are not expected at this time. A
small amplitude ridge will move in on Friday, bringing temperatures
to near seasonal averages.

Another trough will approach from the north on Saturday and cool
temperatures once again aloft. By Sunday and Monday, there remain
chances for precipitation across the region that will continue at
times through next week. There remains uncertainty with model
divergence in the extended forecast period and therefore there is
lower confidence in the details. However, the confidence is high
that troughing over the region will keep conditions cool for the
next 7-10 days at least. Stay tuned...

&&

.AVIATION...
(12Z TAFS)
Issued at 459 AM PDT Wed Sep 11 2024

Mix of MVFR, LIFR, and VFR conditions this morning. The incoming
upper level low pressure system is disrupting the marine layer and
causing stratus to dissipate earlier than previously expected. Low
to moderate confidence that OAK, SFO, SJC, and LVK will stay VFR
through the remainder of the morning. Patchy MVFR-IFR CIGs are
expected to redevelop at APC before VFR conditions return late
morning. VFR conditions will persist for most sites through the
afternoon/evening before stratus and MVFR CIGs return late this
evening. Gusty west to northwest winds are on track to develop by
early this afternoon and continue through the evening. Sustained
winds will generally be between 15 to 20 knots at most airports with
gusts between 20-25 knots. Locally higher gusts between 25-35 knots
are expected at SFO and OAK.

Vicinity of SFO...Stratus is dissipating earlier than previously
anticipated with low to moderate confidence that SFO will stay clear
of CIGs through the remainder of the morning. Gusty west winds
remain on track for SFO and OAK this afternoon with winds
strengthening by late morning and continuing through the evening.
Guidance indicates sustained winds will be between 20-25 knots with
gusts up to 35 knots. Winds are expected to weaken to 10-15 knots
overnight. Some uncertainty remains on timing of stratus return
tonight. Stratus is currently expected to return closer to 08Z but
ensemble guidance suggests it could return closer to 05Z.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Patchy MVFR CIGs are expected to persist
through the late morning. Current satellite observations show
stratus clearing slightly slower in the Monterey Bay Region than
observed in the rest of the Bay Area. However, given the overall
early clearing trend, confidence is low to moderate that CIGs will
clear earlier than currently forecast. Will continue to monitor
satellite observations and adjust the TAFs as needed. VFR conditions
are expected to return by mid to late this morning with stratus
returning early this evening around 00-01Z. Gusty west to northwest
winds remain on track with sustained winds between 10-15 knots and
gusts up to 25 knots expected.


&&

.MARINE...
(Today through Monday)
Issued at 459 AM PDT Wed Sep 11 2024

Widespread gusty north to northwest winds and rough seas continue
over the coastal waters. Significant wave heights will gradually
build to 8 to 10 feet by late Thursday. Gale warnings have been
issued across the inner coastal waters from Pigeon Point to Point
Piedras Blancas and for the Monterey Bay beginning Wednesday
morning  and continuing through Wednesday afternoon. Near gale
force gusts to the occasional gale force gust are possible within
the San  Francisco Bay and across the inner coastal waters from
Point Reyes to Pigeon Point. Unsettled conditions are expected to
continue  through the end of the week, but winds and wave heights
reduce by  the late weekend.

&&

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

     Small Craft Advisory from 9 AM this morning to 3 PM PDT this
     afternoon for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.

     Gale Warning 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 9 PM PDT Thursday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 9 AM PDT Thursday for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 AM PDT this morning for Pt Pinos to
     Pt Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM this morning to 9 PM PDT this evening for
     Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
     to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 AM to 9 PM PDT Thursday for Pt Arena
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Kennedy
MARINE...Kennedy

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NWS MTR Office Area Forecast Discussion