390
FXUS66 KMTR 272317
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
417 PM PDT Sun Apr 27 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 144 PM PDT Sun Apr 27 2025

Shower chances are diminishing across the Bay Area and Central
Coast through the remainder of today. Drier, warmer conditions are
expected Monday through late next week when unsettled weather
returns again.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 144 PM PDT Sun Apr 27 2025

Light showers persist across the southern half of the Bay Area and
Central Coast through early this afternoon. Showers overperformed
along the Central Coast in part due to orographic lifting and in
part due to a lingering moist air mass. Enough moisture lingered in
the wake of yesterday`s low pressure system that light rain showers
were able to continue across the Bay Area and Central Coast today.
The 12Z (5AM) sounding observed a PWAT value of 0.84 inches at OAK
this morning with the daily 12Z mean PWAT value being only 0.78
inches. While only slightly higher than the mean, this was still
more than enough moisture to support continued light rain
development this morning. Shower chances decrease this afternoon
as our moist air mass continues to progress eastward with the
upper level trough and a drier air mass arrives. Notably we will
see drier air advected into the mid and upper levels of the
atmosphere with mid and high level cloud cover expected to
dissipate tonight. Surface conditions, however, look to remain
slightly more moist with drier surface air staying offshore. Moist
conditions in the lower levels and light winds overnight will
result in a high likelihood of fog development tonight along the
coast and across the interior valleys. Fog and low clouds will
likely linger into the early morning commute tomorrow so for those
early morning commuters remember to slow down if you encounter
fog and watch for sudden changes in visibility.

High temperatures across the interior will be in the low to mid 60s
while high temperatures along the coast will largely be in the 50s
today. Tired of below seasonal temperatures? The pattern is set to
change beginning Monday with temperatures warming, becoming more
seasonal, into the upper 60s to low 70s across the interior and
upper 50s to 60s along the coast. Some potential for light offshore
winds on Monday as the trough deepens, becoming more positively
tilted over the Four Corners region. This will result in developing
upper level ridging taking a slightly positive tilt over the West
Coast on Monday before switching to zonal (horizontal) flow Monday
into Tuesday. This will shift our surface winds to be out of a more
N to NE direction (offshore) but winds should remain light due to
persisting high pressure at the surface. Locally breezy conditions
may develop across the higher elevations with gusts up to 25 mph
possible.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 144 PM PDT Sun Apr 27 2025

Surface high pressure and upper level ridging will generally persist
through late next week. Temperatures will continue to warm
Tuesday/Wednesday with seasonal highs in the mid to upper 70s across
the interior and 60s along the coast. Temperatures will start to
trend downwards on Thursday, with highs dropping by 2 to 4 degrees,
before continuing to trend downwards Friday into Saturday as our
next system arrives. High temperatures Friday and Saturday will drop
into the 60s across the interior and upper 50s to low 60s along the
coast. Both the Euro and GFS show a weak cut-off upper level low
dropping into Central/Southern CA in the Wednesday-Thursday
timeframe which will bring decently moist PWATs back to the Bay Area
and Central Coast. Ensembles do not show much in the way of rain
from this weak upper level low, despite the increased moisture, with
drizzle along the coast and a return of low level clouds the most
likely result. Interestingly, the GFS shows this weak cut-off low
merging with a deeper upper level trough that is set to arrive
Friday into next weekend. This system does look to bring light rain
(similar in totals to this weekend`s system) and breezy to locally
gusty winds across the region Saturday into Sunday. The more
impactful component of next weekend`s system is likely to be the
breezy to gusty winds with initial ensemble guidance suggesting
gusts around 40 mph may be possible across the region. There does
appear to be some low level support, with a strong 850 mb jet
setting up along coastal portions of our CWA Saturday into Sunday
and a strong 500 mb jet just offshore. We will get a better idea
about both peak winds and rainfall totals associated with this
system as we get closer to next weekend, so stay tuned!

&&

.AVIATION...
(00Z TAFS)
Issued at 417 PM PDT Sun Apr 27 2025

MVFR to VFR with mid-level cloud ceilings persist through the
overnight hours, with enough moisture retained in the atmosphere to
support the cloud cover overnight. Areas of fog and LIFR ceilings
are possible across the inland valleys and at the coast, but
confidence is low to moderate on the extent and while I considered
lowering visibilities at STS, this is not currently reflected in the
TAFs. Breezy onshore flow should persist into the evening hours.
Clearing of the cloud cover should occur late Monday morning with
breezy onshore winds returning and patchy stratus persisting along
the immediate coast.

Vicinity of SFO... MVFR ceilings continue through the overnight
hours, clearing late Monday morning. Breezy onshore flow continues
into the evening hours before resuming Monday afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR ceilings persist through the
overnight hours, with IFR conditions possible. Ceilings scatter to
VFR late Monday morning, with low confidence of an early return of
stratus to MRY. Breezy onshore winds continue into the evening with
light winds overnight, before the onshore breeze resumes Monday
morning.

&&

.MARINE...
(Tonight through next Friday)
Issued at 417 PM PDT Sun Apr 27 2025

Breezy northwest winds this evening behind the upper low that
brought unsettled weather this weekend. Persistent nw winds
continue Monday, strongest over the outer waters which will
generate steep and fresh seas. High pressure builds this week
keeping persistent nw wind and seas. A stronger front may pass
through the waters by next weekend with building seas.

&&

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

     Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt
     Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM to 9 PM PDT Monday for Pt Arena
     to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT Monday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...DialH
MARINE...RW

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