FXUS66 KMTR 192030
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
130 PM PDT Thu Sep 19 2024

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

.SYNOPSIS...
Issued at 130 PM PDT Thu Sep 19 2024

There remains a chance for showers and thunderstorms across the
interior Central Coast through this evening. A warming trend is on
tap by this weekend and into early next week with temperatures
rebounding to near or slightly above seasonal averages.

&&

.SHORT TERM...
(This evening through Friday)
Issued at 130 PM PDT Thu Sep 19 2024

The upper level low that brought rain showers and thunderstorms to
the interior Central Coast this morning remains south of the
Monterey Bay region. As it moves onshore, there will be a chance of
additional convection this afternoon over the aforementioned region
as the air mass aloft is marginally unstable. The warmest conditions
this afternoon will be across the North Bay and East Bay with
interior areas warming into the low 80's with 60's and 70's as you
move closer to the coast.

The marine layer is projected to deepen tonight bringing low clouds
locally inland to the coastal adjacent valleys. The upper level
trough will push further inland Friday, yet its effects will still
linger with temperatures remaining below seasonal averages. Tomorrow
expecting more widespread 80's across the interior with the
potential for a few spots to reach 90 degrees such as Lake
Berryessa. Elsewhere, 60's and 70's near the coast and San Francisco
Bay Shoreline.

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 130 PM PDT Thu Sep 19 2024

Warming will continue into Saturday and moreso on Sunday as a ridge
of high pressure builds over the eastern Pacific. HeatRisk increase
by Monday and Tuesday with moderate risk across the interior. During
this time, evening clouds will spread into the coastal adjacent
valleys through early morning and then retreat back to the coast by
the afternoon.

&&

.AVIATION...
(18Z TAFS)
Issued at 1057 AM PDT Thu Sep 19 2024

Mix of VFR and IFR-LIFR CIGs across the board. The upper level low
that disrupted the marine layer and brought light rain to our CWA
has moved to the south of us with a slightly more typical stratus
pattern expected tonight. Thunderstorm chances continue to decrease
along the Central Coast but a slight chance persists through the
afternoon. Moderate confidence that stratus will continue to clear
throughout the Bay Area with all sites to return to VFR by 20Z. Low
to moderate confidence in clearing across the Central Coast where
scattered convection continues across southern Monterey County.
Stratus is expected to return early this evening along the Central
Coast and by mid to late evening throughout the rest of the Bay
Area. Low to moderate confidence that MVFR CIGs will reach LVK
overnight with any ceilings that do develop expected to occur after
09Z. Clearing is expected by mid tomorrow morning with most sites
clearing 16-17Z.

Vicinity of SFO...Stratus is clearing out of SFO with northwesterly
winds to pick up over the next few hours. MVFR CIGs are expected to
prevail tonight with ensemble guidance suggesting some potential for
IFR CIGs to develop during the late evening/early morning hours,
however, confidence remains low on IFR development. Stratus is
expected to clear by mid morning with moderate northwest winds
between 12-15 knots expected.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Patchy IFR to LIFR CIGs continue with low
to moderate confidence that CIGs will fully clear around 20Z.
Scattered convection associated with the upper level low is still
located in southern Monterey County and is adding additional
uncertainty to time of stratus clearing at MRY and SNS this morning.
Current thinking is CIGs will at least temporarily clear out this
afternoon with a brief period of VFR conditions. Stratus will return
late this afternoon/early this evening between 00-03Z and persist
through the remainder of the TAF period with MVFR to IFR CIGs. A
slight chance (generally less than 10%) of thunderstorms continues
for SNS through this afternoon. Confidence is too low to include
VCTS in TAFs given that convection is weakening in southern Monterey
county and lightning probabilities are continuing to diminish.

&&

.MARINE...
(Today through Tuesday)
Issued at 907 AM PDT Thu Sep 19 2024

Moderate northwesterly winds continue over the majority of the
coastal waters. Northwesterly winds are expected to strengthen to
fresh to strong and seas will become rougher in the northern
outer waters through the day. Winds and seas remain elevated
through the weekend but ease into the next work week.

&&

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

&&

$$

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

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