612
FXUS66 KMTR 182032
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
132 PM PDT Wed Sep 18 2024

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

.SYNOPSIS...
Issued at 131 PM PDT Wed Sep 18 2024

Isolated to scattered rain showers continue into this evening,
tapering off from north to south gradually through Thursday
afternoon. A warming trend is on tap for by this upcoming weekend
and into early next week with temperatures rebounding to near
seasonal averages.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 131 PM PDT Wed Sep 18 2024

An upper level low remains off of the North Bay coast at this hour
and will continue to drop southward throughout the day before moving
onshore over the Central Coast tonight/tomorrow. As such, much of
the rainfall from this system will remain light and some locations
may not see any rainfall at all! There remains a slight chance of
thunderstorms across the North Bay this afternoon before the
thunderstorm threat focuses on the southern portion of the Central
Coast on Thursday. The threat generally remains less than 15%
however, so confidence of thunderstorm development remains low.

Wrap around moisture from the system as it pushes inland will result
in the continued rain chances (and low end thunderstorm chances) into
tomorrow over the Central Coast but the North Bay and Greater San
Francisco Bay Area are expected to be dry beyond late this evening.
Any thunderstorms that to develop will have the potential to produce
isolated, brief downpours. Temperatures both today and tomorrow will
be 5-15 degrees below seasonal averages.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 131 PM PDT Wed Sep 18 2024

Friday afternoon will still be below normal across the region as the
upper level trough begins to push further inland. The warm-up
doesn`t begin until Saturday with near to slightly below normal
temperatures. Sunday and into early next week is when temperatures
are expected to be slightly above average as high pressure from the
eastern Pacific begins to build inland. The marine layer also looks
to return as a result with night and morning low clouds likely into
next week. Low clouds will the retreat to the coast by the afternoon
each day throughout the week.

&&

.AVIATION...
(18Z TAFS)
Issued at 1112 AM PDT Wed Sep 18 2024

Approaching showers have slowed down slightly but are expected to
reach the Bay Area by late this morning and continue into the
afternoon. Currently a mix of mid-level clouds and MVFR CIGs with
VFR conditions to return during the afternoon/evening. Any showers
that do directly impact airports may result in temporary decreased
visibility and lowered ceilings. Confidence remains low on inclusion
of thunderstorms in TAFs. For all sites except STS, there is a less
then 8% chance of thunderstorms. For STS, thunderstorm chances reach
10-12% beginning early this afternoon through the evening. Shower
chances decrease at all airports except MRY and SNS beginning this
evening with MVFR CIGs expected to return overnight. Light to
moderate southwesterly winds continue into the afternoon before
becoming more northwesterly after cold frontal passage later this
afternoon.

Vicinity of SFO...Scattered showers will arrive within the next few
hours. Any precipitation that reaches the surface will generally be
light but if a stronger shower moves directly over the airport
visibilities may temporarily decrease. A low chance (~5%) of
thunderstorms continues for SFO through this afternoon. Confidence
is too low to include in TAFs but will continue to monitor as
showers start to approach the SF Peninsula. Moderate west to
northwest winds continue with winds weakening slightly overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Scattered showers are expected to move
through the Central Coast through late this evening. Low chance of
thunderstorms (~4-5%) continues through this evening but confidence
remains too low to include thunderstorms in TAFs. MVFR to IFR CIGs
are expected to return later this evening with an early return around
02-03Z. Low to moderate confidence on timing of transition from MVFR
to IFR CIGs overnight. Moderate northwesterly winds are expected
during the day with lighter, variable winds overnight.

&&

.MARINE...
(Today through Monday)
Issued at 924 AM PDT Wed Sep 18 2024

Northwesterly winds will become gusty across the outer waters by
late Wednesday. Seas will be moderate, building to become rough in
the outer waters by Thursday. Unsettled conditions will continue
over the outer waters through the weekend. Showers continue over
the coastal waters through this afternoon. There is up to a 12%
chance for thunderstorms in the mid morning which could produce
lightning, locally heavy rainfall, locally gusty winds.

&&

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

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Kennedy
MARINE...Kennedy

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