000
FXUS66 KMTR 241200
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
500 AM PDT Wed Apr 24 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1228 AM PDT Wed Apr 24 2024

A deep marine layer and expansive cloud coverage will keep
temperatures cool through Thursday before a cold front brings
strong wind on Friday. Clearer skies and slightly warmer
temperatures are expected this weekend.

&&

.SHORT TERM...
(Today through Friday)
Issued at 1228 AM PDT Wed Apr 24 2024

Stratus coverage is quite expansive early this morning due to a
deep marine layer. Some light drizzle is possible along windward
facing slopes this morning, although there hasn`t been any
measurable precipitation so far. The cloud cover will keep
morning temperatures near normal, with high temperatures 5-10
degrees below normal this afternoon.

The weather pattern is fairly dynamic over the next few days. A
persistent low pressure system off the coast of San Francisco
will finally weaken and open up into a trough late today, bringing
the return of NW flow. The supporting upper-level cut-off low
will evacuate to the east on Thursday, allowing a small amplitude
ridge to become established. This high pressure will squish the
marine layer from around 4,000 ft on Wednesday to around 1,500 ft
on Thursday. This change will bring lower, but less expansive
cloud coverage and the potential for morning fog. This regime
won`t last long as a new cold front and associated trough move
will move through on Friday.

&&

.LONG TERM...
(Friday through Tuesday)
Issued at 1228 AM PDT Wed Apr 24 2024

The Weather Prediction Center forecasts the cold front to move
through Friday morning, with a slight chance for light rain on
either side. The biggest impact from this system will be strong NW
wind behind the front. Our official forecast has gale force wind
gusts along the coast of Sonoma, Marin, and Big Sur on Friday
afternoon and evening. NBM probabilities are above 95% of
confirming the previous sentence. All of this has led me to
strongly consider a wind advisory. While there is still some
uncertainty if the threshold will be hit between Marin and
Monterey counties (roughly a 30% chance), I`d rather have the
advisory out with as much lead time as possible to allow the Rocky
Creek slip-out repair crew time to secure the crane for high
winds. The downside of the early issuance is that the coverage
may need to be expanded over the next 24 hours if the rest of the
coast or inland areas start trending higher in the guidance.

Winds will remain strong through the night Friday before gradually
decreasing through the weekend. The cold front will also usher in
a dryer airmass with much less cloud coverage expected this
weekend, especially for inland areas. This will allow
temperatures to return to normal through the weekend and into
early next week.

Some super long range guidance is starting to hint at a potential
storm during the first weekend in May. While there have been some
aggressive deterministic runs lately, the current ECMWF and GEFS
ensemble means both keep the total precipitation under 1/2" at San
Francisco. Even that would be a lot for May, however, which
typically averages about 1/2" for the entire month. The Climate
Prediction Center is also taking note of this and showing
slightly wetter than normal conditions in the 8-14 day outlook
(May 1-7). This is just something to keep an eye on for now.

&&

.AVIATION...
(12Z TAFS)
Issued at 459 AM PDT Wed Apr 24 2024

Low to mid level clouds continue to shroud much of the region.
Despite this, most terminals are currently VFR and expected to
remain so through the evening tonight, though by a slim margin.
Cloud ceilings are likely to continue to hover in the 3200-4000`
range this morning, just barely escaping MVFR CIG thresholds. That
being said, models do favor a few select terminals to see
intermittent MVFR CIGs this morning, namely KOAK and KSTS. Though,
chances of achieving MVFR conditions are only in the 50% range.
Therefore, confidence is low-moderate. Aside from these terminals,
low and mid level clouds will continue to be present through the
TAF period with VFR prevailing. Winds this afternoon will increase
out of the W/SW to become breezy between 10-15 knots. Into the
evening, winds become more westerly but slowly ease. Stratus and
low clouds are expected to filter back inland into the early
morning of Thursday, brining MVFR CIGs for most terminals within
the SF bay and southwards. Slight ridging will help to lower CIG
heights through the nighttime hours of Wednesday into Thursday,
though highest confidence is in maintaining MVFR at this time.


Vicinity of SFO...VFR expected to last through the early morning of
Thursday. There currently stands between a 45-50% chance that KSFO
may see MVFR CIGs develop over the terminal between now and around
17Z. That being said, confidence is highest in maintaining VFR
conditions, though this will be something to watch closely through
the next few hours. Winds SW this afternoon becoming W into the
evening breezy and gusting around 20 knots. Stratus returns in the
early to mid morning of Thursday bringing MVFR CIGs to the SF Bay
region.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR expected to prevail through the evening
of Wednesday, though low to mid level clouds will continue to bring
overcast skies through much of the day today. Confidence on
maintaining VFR is only moderate. Into the afternoon, winds increase
to become onshore and breezy, with gusts upwards of 20 knots likely
at KMRY. Stratus and MVFR conditions return into the late evening of
Wednesday and last through the remainder of the TAF period with CIGs
gradually lowering. At this time, thoughts are that MVFR will be
maintained, though dipping into IFR territory Thursday morning is
not out of the question yet.

&&

.MARINE...
(Today through Monday)
Issued at 459 AM PDT Wed Apr 24 2024

Light to gentle southwesterly breezes continue this morning and
through the early afternoon today. Towards the afternoon, winds
slowly turn to become more northerly and moderate to fresh and
last through the early portion of Friday. Starting Friday
afternoon, northerly winds strengthen to become strong and gusty,
with gale force gusts likely into the late night. Northwest swell
continues to move through the waters this week with a period of
about 10-12 seconds. Small southerly swell with a period of about
14-16 seconds persists through the week as well.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 PM this evening to 9 AM PDT Thursday
     for Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 AM to 9 AM PDT Thursday for Pigeon
     Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...AC
MARINE...AC

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