Technical NOAA Weather Discussion

FXUS66 KMTR 251157
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
457 AM PDT Thu Apr 25 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1201 AM PDT Thu Apr 25 2024

Cool temperatures will continue today. A cold front will bring 
a chance for light rain beginning tonight, with strong winds 
Friday night. Increasing sunshine will kick off a warming trend 
Sat-Tue.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1201 AM PDT Thu Apr 25 2024

A coastal surface trough will continue to weaken and move inland,
allowing a low-amplitude ridge to build. This will cause the 
marine layer to compress to about 1,500 ft. Compared to the 4,000
ft deep marine layer observed Wednesday, the low overcast today 
will be more limited to the coast and adjacent low valleys. The 
standard NW flow will also return as the trough weakens. The cool 
temperatures will continue, with highs generally in the 60s. This 
ridge pattern will be short lived as a cold front moves through on
Friday.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 1201 AM PDT Thu Apr 25 2024

Some light rain is possible starting ahead of the cold front
Thursday night, with low PoPs lasting though the day Friday. 
22/26 members of the SREF have some precipitation falling at SFO 
between Thursday night and Friday, but only 4 of them are above 
0.05" of accumulation, and none of those are above 0.1". Similar 
results are found throughout the Bay Area, with slightly more
bullish results along the Central Coast. As such, I have 
increased the NBM PoPs to at least 15% to ensure a slight chance 
of rain is mentioned, but did not increase the QPF from the WPC 
guidance, which is near zero. There's a decent chance some rain 
falls late Thursday-Friday, but it will be light.

The bigger impact will be from strong NW winds behind the cold
front. 24 hours ago, it looked like a slam dunk wind advisory
along the coast, but the models have backed off since then. NBM is
on the high side of the guidance, but only shows a slight chance
of exceeding 40 mph gusts along the coast on Friday night. The 
timing of the strongest winds has also shifted from Friday 
afternoon to overnight Friday. Based on this, and the fact that 
other deterministic models are even less aggressive, we are not 
hoisting a wind advisory at this time. That being said, there will
be plenty of gusts above 30 mph on Friday and Saturday with some 
minor impacts expected.

The weekend will feature clearing skies and slightly warmer
temperatures, although Saturday will still be breezy. The gradual
warm-up will continue through early next week, as the region
returns to seasonal temperatures under mostly clear skies. The 
next threat of rain arrives late next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 457 AM PDT Thu Apr 25 2024

MVFR conditions persist through the late morning for most terminals 
with westerly winds steadily increasing through the day. Most 
terminals will see CIGs lift to VFR conditions late in the morning 
of Thursday, with winds steadily increasing out of the west to 
become moderate to strong, and gusting 20-25+ knots well into the 
evening. KSFO is likely to see the strongest gusts nearing 30 knots. 
Aside from strong winds and gusty conditions, models continue to be 
in good agreement that stratus will push inland in the early evening 
near 00Z-02Z Friday. Strong onshore winds help advect these low 
clouds inland, bringing widespread MVFR conditions once more that 
are expected to last through the end of the TAF period for most 
terminals. 
   
Vicinity of SFO... Expect MVFR CIGs to last into the late morning 
before brief lifting to VFR briefly for a few hours into the 
afternoon. Some models seem to suggest KSFO remaining MVFR through 
the TAF period, though highest confidence is in CIGs improving to 
VFR conditions beginning in the late morning and lasting through the 
late afternoon. Despite improvement to VFR conditions, low to mid 
level clouds will continue to be present throughout the duration of 
the TAF period. Winds will begin to strengthen and gust 25+ knots 
out of the west this morning, with winds continually strengthening 
into the early afternoon. MVFR CIGs will return in the early 
evening, as stratus is ushered in by strong westerly winds. MVFR 
then lasts well beyond the end of the TAF period with winds slowly 
decreasing into the late night to around 12 knots.  

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...KMRY improves from IFR to MVFR later this 
morning as CIGs begin to lift beyond sunrise. Coastal drizzle that 
has impacted terminals overnight will also begin to cease beyond 
sunrise. Stratus will continue to shroud area terminals through the 
day today with no improvement to VFR expected. Chances of VFR are 
only in the 30-40% range, therefore have gone with MVFR prevailing 
through the entire TAF period for KMRY, and only brief clearing to 
SCT for KSNS. However, confidence in KSNS clearing to VFR is low. 
Winds onshore, moderate, and gusting to around 20-25 knots beginning 
in the late morning and continuing through the late night tonight. 
Stratus and MVFR CIGs last well into the morning of Friday, with 
coastal drizzle making a return. 


&&

.MARINE...
(Today through Tuesday)
Issued at 457 AM PDT Thu Apr 25 2024

Moderate northwesterly winds persist through Friday morning with
occasional fresh to strong gusts throughout portions of the
coastal waters. Winds strengthen to become strong and gusty into
Friday afternoon with gale-force gusts likely near the Big Sur
coast. These strong and gusty northwesterly winds last through the
weekend and into at least the early portion of next week, bringing
hazardous conditions for small craft. Moderate period northwest
swell will continue to move through the waters this weekend, with
a new longer period northwest swell train entering the waters
Sunday. Light, long period southerly swell continues through end
of forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM this morning to 9 PM PDT this 
     evening for Mry Bay.

     Small Craft Advisory from 9 AM to 3 PM PDT Friday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 
     NM.

     Small Craft Advisory until 3 PM PDT this afternoon for Pigeon Pt 
     to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes 
     to Pigeon Pt 0-10 nm.

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

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

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

&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Thu Apr 25 06:30:03 PDT 2024
From the National Weather Service