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

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FXUS66 KMTR 261757

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1057 AM PDT Thu Apr 26 2018

.SYNOPSIS...Upper low off the coast will keep temperatures below
normal through the end of the work week and into the weekend. Some
coastal drizzle or very light showers possible later tonight
through early Saturday as the upper low moves onshore, however
most areas will remain dry with below normal temperatures being
the main impact. Cool and dry pattern continues into early next

&& of 8:53 AM PDT Thursday...Yet another cloudy
morning for much of the area as the central California coast
remains under the influence of a deep marine layer in excess of
2,000 ft. Visible satellite imagery shows the cloud deck pushing
well into the Salinas Valley, some of the East Bay Valleys
including the Livermore area, as well as the North Bay Valleys.
Expect the clouds to mix-out through the morning with many areas
away from the immediate coastline clearing out before lunch. An
upper level low largely responsible for deepening the marine layer
is currently near 35N/135W, or about 700 miles west of San
Francisco. Temperatures with afternoon will be a few to several
degrees cooler for most locations with coastal areas in the 50s
and 60s and interior areas in the 60s and 70s. No major changes
planned for the morning update with the short-term remaining on
track. For additional details, please refer to the previous
discussion section.


.PREV of 3:27 AM PDT Thursday...Marine layer now in
excess of 2000 feet with fog product showing another good push of
stratus into most inland valleys. Upper low well off the coast is
responsible for the deep marine layer and below normal temperature
pattern. Unseasonably cool highs today with 60s near the
coast/bays and only some low to mid 70s inland. The low will
slowly approach the coast tonight into Friday. As this occurs some
coastal drizzle may occur as the marine layer continues to deepen
overnight into Friday as initial vorticity lobs passes over the

Core of upper low looks to move onshore near Cape Mendocino on
Friday with continued slight chance of some coastal drizzle in
deepening marine layer environment. Light showers associated with
the instability aloft will be confined to the far North Bay,
mainly later Friday night Saturday morning. Daytime highs Friday
and Saturday continue to be unseasonably cool with deep marine
layer, substantial clouds and a cool airmass aloft leading to lots
of daytime highs only in the 60s throughout the Bay Area.

The main low finally ejects eastward late Saturday night into
Sunday. So for the weekend Sunday looks to have more sunshine and
slightly warmer temperatures.

Longwave trough stays over the West Coast with a cold but dry
shortwave dropping towards the Central Coast by Monday and
Tuesday. This will continue to keep temperatures on the cool side
of normal through the end of the month but no precip expected with
this upper level shortwave. Modest warming and drying trend by the
middle of next week but no hot weather nor storms of note in


.AVIATION...As of 10:55 AM PDT Thursday...for 18z TAF. The region
is once again under the influence of a marine layer around 2,000
feet in depth. However, inland cloud cover is slowly dissipating
this morning and will do so into the early afternoon with VFR
conditions returning to most terminals. Onshore winds will
strengthen slightly for the afternoon and evening becoming breezy
to locally gusty. Winds relax slightly late this evening with the
potential for an earlier return of stratus ahead of an approaching
mid/upper level system.

Vicinity of KSFO...VFR conditions with winds becoming breezy to
locally gusty through the evening. Low clouds potentially return
earlier than previous mornings with low/moderate confidence on
timing. Once stratus returns, look for MVFR CIGS through around
18Z Friday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR CIGS will continue to dissipate
through 19Z with VFR conditions thereafter. Onshore winds will
strengthen slightly for the afternoon and evening becoming breezy
at times. Winds diminish late this evening with low clouds
returning around or before 03Z Friday.

&& of 8:37 AM PDT Thursday...Generally light west to
northwest winds will prevail with locally breezy conditions near
the coastal gaps and prominent points this afternoon and into
Friday. Light to moderate seas will continue through the forecast
period with a mixed south and northwest swell developing late in
the week.





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