194
FXUS66 KMTR 140000
AFDMTR

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

...New AVIATION, 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.

&&

.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...
(Tonight through next Saturday)
Issued at 459 PM PDT Mon May 13 2024

  Moderate to fresh breezes out of the northwest through at least
the midweek, then ease to become gentle to moderate, and more
southwesterly. The far northwestern outer waters may occasionally
gust stronger to gale force late tonight and early Tuesday
morning, but afterwards weakens. Fair weather continues, though
marine stratus will create overcast skies through much of the
week. Significant wave heights will continue to build to 12-15
feet in the northern outer waters by Tuesday. As a result,
conditions in the outer waters will be hazardous for small craft
during the early portion of the week. Wave heights then gradually
diminish into the late week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Pinos to
     Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 AM PDT Tuesday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Kennedy
MARINE...AC

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