FXUS66 KMTR 301135

Area Forecast Discussion
National Weather Service San Francisco Bay Area
435 AM PDT Fri Sep 30 2022

.SYNOPSIS...Another day of moderate warming on this Friday with
high pressure building. Light offshore flow. A shallow coastal
marine layer will continue however, with some areas of morning
low clouds and patchy fog near the waters. Cooling trend this
weekend as onshore flow returns. Gradual warming trend starts
again Monday and should persist next week as high pressure remains
the dominant influence.


.DISCUSSION...as of 03:44 AM PDT Friday...Nighttime satellite
imagery shows a shallow layer of marine stratus along the Big Sur
Coastline and curling into the southern half of Monterey Bay.
These low clouds are causing some patchy fog around the Monterey
Peninsula which could persist into the morning commute hours so be
cautious if driving in that region in case visibilities vary
along the road. To the north (Watsonville, Santa Cruz, and
northward along the SF Bay Area coast) skies remain fairly clear.

High pressure ridging remains along the west coast which is
aiding in the the compressed marine layer. Daytime highs today
should be similar to yesterday or a touch warmer. Highs today will
be in the mid 80s to low 90s across the interior while coast and
bay shorelines stay in the upper 60s to mid 80s. Expect some
light offshore flow today mainly around Napa County and into
portions of the East Bay, but these winds should remain around 10
mph or less. Those areas should return to an onshore flow regime
this evening after around 5 or 6 pm.

That high pressure ridge axis along the west coast will weaken
over the weekend as the onshore winds and marine layer re-
establish. This will allow for temperatures to cool Saturday and
Sunday such that Sunday highs will be more seasonable: 60s to mid
70s along coast and bay shorelines while inland areas range mid
70s to mid 80s.

As we start the work week on Monday, the ridge axis rebuilds and
shifts inland. It will linger through much of next week and cause
a very gradual warming trend from Monday into Friday as dry
conditions persist. By the end of next week, daytime highs will
be back into the low 90s for the far interior with 70s to 80s
closer to the coast. Many of the ensembles are in agreement with
that ridging pattern being the dominant synoptic pattern so
there`s good confidence in this gradual warming trend. In
addition, the CPC temperature outlook shows that much of the west
should lean towards above normal temperatures. As we get towards
the end of next week, it looks like daytime highs across the
interior will generally range about 5 to 10 degrees above normal.
However, the forecast HeatRisk will remain in the Low category
with some patchy areas of Moderate. This means that folks
sensitive to heat should ensure they stay cool and hydrated while
the general population should not be impacted much by the warmer
than normal temps.


.AVIATION...As of 4:30 AM Friday... For the 12Z TAFs. Fog and stratus
LIFR-VLIFR over Monterey Bay, extending southward just off the
coast of Monterey County, but otherwise VFR throughout the region.
Expect the sole patch of stratus to burn off by 17z, followed by a
breezy day with winds in a generally onshore, westerly pattern.
Clouds return overnight to the region, but the bulk of the
development will be just after the 24-hour TAF period.

Vicinity of SFO... VFR through the TAF period. West winds pick up to
14 knots in the afternoon with gusts up to 20 knots. Stratus returns
via the Golden Gate this evening, but is presently expected to
impact the East and South Bay more readily than over SFO itself,
where confidence in ceiling impacts is low.

KSFO Bridge Approach... On Friday evening, expect stratus to set up
over the East Bay coast starting around 09z.

Monterey Bay... Low stratus at MRY expected to continue until 17-
18z. At SNS, a patch of low stratus set up over the terminal for the
9z hour but was shooed away by light easterly valley drainage winds.
Low confidence that stratus develops over SNS again tonight. Winds
this afternoon breezy from the northwest, then expect a few low
clouds over the terminals in the evening before stratus returns in
the overnight hours. In particular, MRY might once again reach LIFR
or even VLIFR ceilings and visibilities.


.MARINE...as of 04:34 AM PDT Friday...Gusty northwest winds
decreasing across the waters this morning  with exception of
lingering gusty northwest winds over the  northern waters. Winds
creating steep, hazardous seas with wave  heights 9 to 10 feet in
the outer waters this morning. Winds and  seas diminishing through
the weekend.


     .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm until 9 AM




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NWS MTR Office Area Forecast Discussion