Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 121155

Area Forecast Discussion
National Weather Service San Francisco Bay Area
455 AM PDT Mon Apr 12 2021

.SYNOPSIS...Another warm and sunny day is on tap for Monday, after
morning low clouds burn off. Gusty winds return Monday evening and
last through Tuesday night. Temperatures cool off for Tuesday
before recovering in the midweek. Dry and seasonable conditions
persist through the forecast period, with increasing temperatures
likely next weekend.

&& of 02:42 AM PDT Monday...The marine layer has
allowed for some stratus to form in the late night. Areas affected
include the coastal side of the SF Peninsula, the Monterey Bay,
and northern portions of the Big Sur Coast. This cloud cover looks
to spread into the SF Bay and the Salinas Valley going into the
morning before burning off as the sun rises. Monday morning`s lows
will be slightly warmer overall than the last few mornings, but
still close to average for this time of year.

Monday afternoon offers clearing skies as well as similar, yet
slightly cooler temperatures compared to Sunday. This will place
coastal areas in the low 60s while more interior areas will favor
the 70s. A few isolated interior locations could peak in the low
80s, but this level of warmth does not look widespread. While
showing fairly similar conditions to Sunday, Monday evening does
offer a change of pace for the forecast.

A low pressure will build to the Northeast Monday evening,
introducing a more north to northwesterly flow and increasing the
pressure gradient. These changes in pattern will provide gustier
winds starting Monday evening and lasting into Tuesday night. The
pattern change will also allow for a cooler airmass to enter the
region, meaning Tuesday afternoon`s highs will be a few degrees
below Monday`s peak temperatures.This will make Tuesday the coolest
day of the forecast, but temperatures will still be around average
with highs ranging from the low 60s at the coast and the low 70s in
more interior areas.

Getting back to the winds: higher resolution models place the peak
gusts on Tuesday afternoon. Gusts will approach 30 mph along
portions of the Marin, San Francisco, and San Mateo county coasts,
while the strongest winds (approaching 45 mph) look to stay more out
to sea. For now the winds that will make it on land do not look to
meet wind advisory criteria, but this will be something the
forecaster team will keep an eye on.

Winds will back off and temperatures will begin to recover into the
mid week. Daytime highs will return to offer the 60s at the coast
and 70s for more inland areas, until the weekend, where models and
ensembles are calling for another warming trend that could lead to
temperatures 5 to 10 degrees above average. Much can change between
now and then, but recent model and ensemble updates as well as the
CPC outlook are increasing confidence in a warm start to the third
week of April.

Lastly, the forecast continues to offer dry conditions. While there
is some slight hope that the marine layer could introduce light early
morning drizzle in the next few days, actual wetting rain remains
out of the forecast.


.AVIATION...As of 04:55 AM PDT Monday...For the 12Z TAFs.
Forecast mostly on track with the marine layer outperforming
model/ensemble data with areas on SREF/HREF >20% ceiling probs
filling in and overall much weaker winds versus 24hrs ago as of
12Z. Satellite imagery shows fingers of stratus extending deeper
into locations such as the North Bay (KSTS- OVC009 KAPC- OVC011)
through the Golden Gate/Point Reyes gaps, the extreme southern
Salinas Valley (has nearly reached KPRB), and a SSW to NNE feed
through the San Bruno gap into the East Bay hills which is now
attempting to wrap clockwise towards KSJC at this hour. Latest TAF
package features somewhat more pessimistic borderline MVFR/IFR
ceiling scenarios with clearing times of 16-18Z (earlier in SF Bay
Area/later in the Central Coast) including for terminals that
remained VFR last night. KSFO will remain on the southern fringe
of the layer through the morning so can not rule out patchy/tempo
SCT-BKN conditions there through at least sunrise. Moderate
onshore winds today becoming locally gusty tomorrow, especially
near KSFO and the north coast.

Vicinity of KSFO...VFR. Light onshore winds this morning becoming
breezy to occasionally gusty in the afternoon. Similar flow
pattern to last night with SSW to NNE push of marine stratus
through the San Bruno gap and towards KOAK/east Bay Hills while
bypassing KSFO to the north. Like this morning, could see very
brief patchy SCT/BKN cigs around sunrise. Stratus not as favorable
for Monday night into Tuesday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Borderline IFR/MVFR OVC cigs through
18Z, then VFR but remaining cloudy near the bay. Light to locally
breezy onshore winds. Marine layer with IFR/MVFR cigs return

&& of 04:43 AM PDT Monday...Northwesterly winds will
ease across the waters today, especially near the coast. Then,
northwesterly winds rebuild tonight and through Tuesday,
especially from Point Reyes northward where near to gale force
wind gusts will be possible. A moderate northwest  swell has
arrived and will merge with the steep wind waves,  especially in
the northern and outer waters making for steep combined seas
primarily in outer waters north of Point Reyes.


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




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