-- Discussion containing changed information from previous version are highlighted. --
312
FXUS66 KMTR 140404
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
904 PM PDT Mon May 13 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 1217 PM PDT Mon May 13 2024

Relatively quiet pattern persists through the forecast period with
morning marine stratus and clear skies elsewhere. Inland
temperatures warm into the 70s and 80s each afternoon with a
persistent marine layer keeping coastal highs in the 60s.

&&

.UPDATE...
-- Changed Discussion --
Issued at 903 PM PDT Mon May 13 2024

Did a few minor tweaks to the forecast this evening to cool
temperatures by a few degrees across the interior for tomorrow. This
is as the past couple of days did not reach our actual forecast
temperatures for inland areas. Low clouds will penetrate well inland
into the valleys overnight and begin to mix out by mid-to-late
morning. With the marine layer sitting at around 1,600-1,800 feet
per the Fort Ord Profiler, temperatures tomorrow afternoon will
likely reach the mid 70`s to mid 80`s in far inland areas with 60`s
near the coast.
-- End Changed Discussion --

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 1217 PM PDT Mon May 13 2024

A weak upper low continues to slowly traverse into the southwest
US while gradually deepening our marine layer. The main result of
this will be a slightly greater extent of marine stratus inland.
However, the overall pattern continues to be dominated by a stout
longwave ridge over the Eastern Pacific, so afternoons will be
clear across the area with stratus lingering along coastal areas.
Afternoon highs in the 70s for most and 60s along the coast.
Farther inland locations such as southern Monterey county eastern
Contra Costa county, and northern Napa counties will see highs in
the mid-to-upper 80s.

&&

.LONG TERM...
(Tuesday night through next Sunday)
Issued at 1217 PM PDT Mon May 13 2024

Through midweek, the ridge pattern strengthens slightly as the
weak upper low pulls away. Though the ridge influence will be
dominant, we remain on the periphery, so there is no strong signal
for a pronounced warming trend through the week. Instead,
afternoon highs will increase just by a few degrees from midweek
into the weekend. Most areas will see the mid-70s with inland
locations in the lower 80s. A few of the aforementioned warmest
locations have a shot at hitting the 90 degree mark. Lows will
generally be in the lower to mid 50s. Coastal clouds are likely
during the overnight and AM hours with a gradual clearing towards
the coast each afternoon.

&&

.AVIATION...
(00Z TAFS)
Issued at 459 PM PDT Mon May 13 2024

VFR to MVFR-LIFR overnight. Similar to yesterday, widespread stratus
coverage is starting to move into coastal region and the Fort Ord
wind profiler shows the top of the marine layer to be around 1500-
1600 feet. This increases confidence that stratus will again be
widespread inland and will likely reach all stations. Guidance is
split on if stratus will reach LVK with the GFS showing an increase
in RH and weaker winds 10-16Z which may help lower CIGs develop.
Given forecast guidance and persistence, leaning towards stratus
reaching LVK for a short period from the early to mid morning hours.
Elsewhere, high end IFR to low end MVFR CIGs will initially develop
during the late evening before CIGs lower and VIS drops overnight.
Increased fog potential at STS, MRY, and SNS with guidance
indicating significant visibility overnight/during the early morning
hours. Across the north bay winds will stay out of the south to
southwest, elsewhere winds are largely west to northwest.

Vicinity of SFO...Currently VFR transitioning to MVFR-IFR overnight.
ECMWF ensemble guidance indicates higher gusts close to 25 knots
will continue through ~03-04Z with winds expected to drop off after
that time. Low to moderate confidence on exact timing of stratus
arrival to SFO. Earlier guidance suggested an arrival between 03-05Z
but newer guidance has pushed stratus arrival back closer to 08-10Z.
Looking at both persistence and GFS guidance - leaning towards
stratus arrival around 08Z but some uncertainty remains. Will
continue to monitor stratus progression and revise as needed.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR transitioning to LIFR overnight.
Initial stratus push is expected to have MVFR-IFR CIGs with CIGs
lowering moving into the late evening/overnight. Increased fog
potential for MRY and SNS heading into the early morning hours.
Guidance indicates visibilities may drop to 1/2SM but confidence was
on the lower end. For the next TAF issuance, will continue to assess
trends and fog potential. Winds will stay out of the west to
northwest wind. Winds will weaken overnight before moderate winds
return by late tomorrow morning.

&&

.MARINE...
-- Changed Discussion --
(Tonight through next Sunday)
Issued at 903 PM PDT Mon May 13 2024

Moderate to fresh northwesterly winds continue through the middle
of the work week before diminishing to gentle to moderate
beginning Wednesday. Occasional near gale force to gale force
gusts are possible across portions of the northern outer waters
overnight Monday into Tuesday morning. Winds will become more west
to southwesterly and gusts are expected to strengthen across the
northern outer waters heading into the late week and weekend.
Overcast conditions and widespread stratus continue across the
coastal waters as surface high pressure builds. Significant wave
heights across the central and northern outer waters will build to
10-14 feet by mid- week before seas diminish by late week.
-- End Changed Discussion --

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CA...None.
PZ...Small Craft Advisory until 9 PM PDT Tuesday for Pt Arena to Pt
     Reyes 10-60 NM.
-- End Changed Discussion --

&&

$$

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

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