Small Craft Advisory 182, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
459 PM PDT Wed Sep 5 2018

.SYNOPSIS...The marine layer and onshore flow will weaken slightly
through late week as high pressure builds over the region. This will
allow for inland warming with temperatures climbing back to above
seasonal averages, peaking on Friday. An upper level trough is then
forecast to impact the region early next week and result in a coo-
down.

&&

.DISCUSSION...as of 01:35 PM PDT Wednesday...A deep marine layer
and onshore flow has allowed for low clouds to remain in place
along our entire coast, into the coastal North Bay, through the
Golden Gate Bridge and around the Monterey Bay. This has held
temperatures down in these areas with inland areas also similar to
a few degrees cooler compared to 24 hours ago. Forecast maximum
high temperatures in areas of cloud cover may be a bit too high
and may need to be lowered if cloud cover does not mix out.

Given the above, look for extensive cloud cover once again region-
wide this evening as stratus spread inland into the valleys this
evening and overnight. While confidence is low, coastal drizzle may
be possible overnight as the marine layer compresses slightly. As
high pressure south of the region over the Pacific builds northward
and toward the coast on Thursday, a slight warming trend is forecast
for the interior. A more robust warming is likely on Friday as the
ridge strengthens and marine influence/onshore flow weakens. This
should allow for inland temperatures to warm back above seasonal
averages into the 80s and 90s while coastal areas warm into the 60s
and 70s. Cannot rule out our warmest interior areas reaching to
around 100 deg F by Friday afternoon. Temperatures moderate slightly
for the weekend yet will remain warm to very warm across the
interior.

Medium range guidance are now indicating a deeper mid/upper level
trough will drop southward down the Pacific Northwest coast and
across our region sometime early next week. This would bring a
cooling with temperatures falling back below seasonal averages by
Tuesday and Wednesday of next week. If this hold true, the marine
layer may very well mix out and result in less widespread cloud
cover each afternoon. If this occurs, temperatures may be more
uniform region wide as warming could occur near the coast. Aside
from the potential for coastal drizzle the next few nights, dry
weather conditions are likely to persist through the forecast
period.

&&

.AVIATION...as of 4:45 PM PDT Wednesday...Ft Ord Profiler shows
the marine layer has deepened to over 2000 feet this afternoon.
The onshore gradients have increased as well. This suggests an
earlier return of stratus to the SFO Bay Area tonight. Because the
onshore gradients are northwest instead of west clouds will not
come in super early. Current thinking is around 06Z for cigs into
SFO and the approach.

Vicinity of KSFO...MVFR after 06Z. West winds to 18 kt through
04Z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR ceilings have persisted all day
and based on satellite imagery clearing is not likely. Bases will
be higher tonight due to a deeper marine layer. MVFR cigs may
barely drop into IFR range after 04Z.

&&

.MARINE...as of 04:45 PM PDT Wednesday...Light winds will continue
to prevail over the coastal waters  into Thursday before northwest
winds increase late week. Light  northwest seas overnight with
heights 5 to 7 feet at 9 to 10  seconds.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...NONE.

&&

PUBLIC FORECAST: RGass
AVIATION: W Pi
MARINE: Rowe

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