466
FXUS66 KMTR 120812
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
112 AM PDT Mon May 12 2025

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

.SYNOPSIS...
Issued at 100 AM PDT Mon May 12 2025

Unsettled weather continues today with strong and gusty onshore
winds, light rainfall, and a less than 15% chance for
thunderstorms.

&&

.SHORT TERM...
(Today and Tuesday) Issued at 100 AM PDT Mon May 12 2025

A cold front with upper-level support will be the name of the game
over the next two days. Said cold front remains just off the
California Coast with rain just beginning to reach the ground in
Mendocino County (just to the north of our CWA). Cloud cover and
light rainfall will expand in coverage through the morning.
Rainfall totals will have a northwest to southeast gradient of
0.20" to 0.00" respectively with locally higher totals in the
higher terrain of the Bay Area. Interior Monterey and San Benito
Counties may not receive measurable precipitation, but light
drizzle can be expected, especially in the higher terrain with the
help of orographic lift. Strong and gusty onshore winds will
continue with the strongest winds expected in the higher terrain,
gaps, and passes where gusts up to 40mph are expected. Widespread
gusts of 20-30mph can be expected elsewhere. The post-frontal
environment will have a low probability (<15%)/high impact threat
for thunderstorms. If a thunderstorm were to develop the threats
include lightning, small hail, and locally heavy rainfall and
gusty winds.

&&

.LONG TERM...
(Wednesday through Sunday) Issued at 100 AM PDT Mon May 12 2025

Heights will be slow to rebuild Wednesday as the open wave exits to
the east. There still remains uncertainty in the extended forecast
as an upper-level shortwave ridge building into the Eastern Pacific
Ocean Thursday quickly gets flattened by an upper-level shortwave
trough in the Gulf of Alaska by Friday. These two features will
propagate through the upper-level pattern and are resulting in 33%
of global ensemble members suggesting an inside slider like
pattern setting up over the weekend with the ECMWF and Canadian as
the primary drivers. As of now they are forecasting the upper-
level low only reaching the Northern Great Basin and remaining
progressive. Any further digging, strengthening, or westward
solution will likely result in more impacts if it were to come to
fruition.

&&

.AVIATION...
(06Z TAFS)
Issued at 919 PM PDT Sun May 11 2025

Low clouds along a cold front arrive tonight and Monday morning
along with showers, perhaps steady rain at times especially e.g.
at Santa Rosa Airport with a combination of upsloping southerly
wind and weak pre-frontal warm sector arriving before the cold
front producing IFR-MVFR in rain. Showers extend to the south to
the north Central Coast Monday. Improving conditions to VFR return
during the afternoon and evening. Gusty west to northwest winds
redeveloping Monday afternoon and evening.

Vicinity of SFO...VFR continues through the evening, thereafter a
lower cloud ceiling and visibility /MVFR/ develops with showers
mainly Monday morning, a few lingering showers are possible in the
afternoon. West wind gusts to near 25 knots this evening, decreasing
after 04z to around 10 knots, west wind increasing Monday afternoon
and early evening with gusts to 25 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR continues through early to mid evening,
thereafter patchy low clouds /VFR-MVFR/ forming near the terminals
due to ongoing onshore winds, upsloping and lower level cool air
advection. By early Monday morning low clouds will have a better
chance of forming and there may be a few showers Monday. Generally
VFR-MVFR during the 06z TAF cycle.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 915 PM PDT Sun May 11 2025

A much cooler air mass will continue to move in from the northwest
tonight with a reinforcement of cooler air arriving behind a cold
front Monday. Showers will accompany the cold frontal passage
beginning early Monday, with showers then diminishing later in the
day Monday. Northwest winds will become gusty mid to late week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 AM PDT
     Tuesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt
     Reyes 0-10 nm.

     Small Craft Advisory until 3 AM PDT early this morning for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

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

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa

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