196
FXUS66 KMTR 252109
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
209 PM PDT Wed Sep 25 2024

...New SYNOPSIS, SHORT TERM, LONG TERM...

.SYNOPSIS...
Issued at 104 PM PDT Wed Sep 25 2024

Mild weather today under a deep marine layer. Warming trend begins
tomorrow, much warmer by Friday. High temps near or above average
persist into next week.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 104 PM PDT Wed Sep 25 2024

Quick check of current temps shows about 15-30 degrees cooler than
24 hours ago, depending on where you are. All thanks to a deep
marine layer and robust onshore flow in response to a passing
upper level trough in the Pacific Northwest. This pattern evolves
rather quickly back to a ridge setup with effects beginning
Thursday. High temps start to trend upwards Thursday as the marine
layer becomes compressed and cloud cover clears sooner in the day,
compared to today. Temperatures Thursday look to be about seasonal
normals. Some high clouds may end up in the picture this evening
for locations in the North Bay, making for a nice sunset if you`re
inland or above the stratus.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 104 PM PDT Wed Sep 25 2024

Friday is expected to be the warmest day headed into the weekend
with highs ranging 5-15 degrees above normal. There`s a short
window of a weak offshore gradient that will likely set up in the
morning, eroding most of the marine layer and causing temps to
increase rapidly. By the afternoon, the gradient will reverse and
breezy onshore flow will ensue. Therefore, there is more
uncertainty than normal with the highs on Friday based on the
timing of the wind reversal. A progressive Gulf of Alaska trough
pattern remains through the weekend with another upper level
disturbance heading into the PNW Saturday and Sunday. This will
aid in flattening the ridge influence, bringing high temps back
down towards normal. However, the roller coaster ride continues
with a ridge influence building back in through early next week,
resulting in another warming trend. Ensemble guidance shows fairly
reasonable agreement in this pattern, so confidence is high that
we will see above average temperatures at least through the middle
of next week.

&&

.AVIATION...
(18Z TAFS)
Issued at 1024 AM PDT Wed Sep 25 2024

Thanks to an extensive marine layer already 2000-2500 feet deep and
deepening, extensive IFR-MVFR stratus covers the inland valleys,
beginning to mix out along the edges. Most terminals should clear to
VFR by 18-19Z with ceilings persisting through the TAF period at the
immediate coast. Breezy onshore flow will develop this afternoon and
evening, with stratus returning to the inland valleys tonight,
starting to mix out by the end of the 24-hour TAF period.

Vicinity of SFO... Terminal has cleared out and should remain VFR
for the rest of the day. West-northwest winds develop this afternoon
gusting to 15-20 knots, before winds diminish in the late evening
hours. MVFR stratus will return this evening and mix out late
Thursday morning, followed by afternoon winds gusting to around the
same speed as today.

SFO Bridge Approach... Some lingering stratus could impact the
approach path for the next hour. Otherwise similar to SFO.

Monterey Bay Terminals... IFR-MVFR stratus continues to around 19Z
at SNS, closer to 20-21Z at MRY. Breezy onshore flow develops in the
afternoon and diminishes in the evening, as MVFR stratus returns to
the region. Model output is showing potential for reduced
visibilities, but a deep marine layer should keep fog concerns at
bay.

&&

.MARINE...
(Today through Monday)
Issued at 1024 AM PDT Wed Sep 25 2024

Light to gentle northwesterly breezes continue today.
Northwesterly breezes strengthen to become moderate to fresh and
seas rebuild to become rough in the outer waters by Thursday
through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM Thursday to 9 AM PDT Friday for
     Pt Arena to Pt Reyes 10-60 NM.

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

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...DialH
MARINE...DialH

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