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

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FXUS66 KMTR 210536
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1036 PM PDT Sun May 20 2018

.SYNOPSIS...An upper level low over California will keep below
normal temperatures, albeit warmer than this weekend, through the
first half of the week. Another upper level approaches the later
half of the week and into the weekend with onshore winds keeping
temperatures on the cool side of normal while mainly dry
conditions are forecast.

&&

.DISCUSSION...as of 9:00 PM PDT Sunday...Temperatures across the
region were fairly similar to yesterday with most reporting
temperatures within a few degrees of yesterdays highs.
Temperatures didn`t climb much, if at all, this afternoon with
highs only reaching the mid 50s to around 60 along the coast and
bays and 60 and 70s inland. Abundant morning clouds and a
moderately strong onshore gradient maintained a steady stream on
cool marine air moving inland and clouds lingering well into the
late afternoon and evening. Widespread low clouds are anticipated
once again tonight with lows in the 40s to low 50s overnight.

From previous discussion...Looking forward the last few nam runs
have generated some coastal drizzle tonight with cyclonic flow
aloft and moist onshore flow lifting the boundary layer. Coastal
hills from San Mateo southward to Monterey that are exposed to nw
winds off the ocean is where the modeling is showing some
measurable drizzle type qpf that should it develop will be
localized.

Main forecast theme to start the work week will be continued below
normal temps and breezy onshore winds. The North Bay may see the
most sunshine on Monday with drier north/northeast flow around
the upper low. MOS data showing 79 degrees for Santa Rosa on
Monday while most cities around the Bay will see 60s once again
with some lower 70s for the Santa Clara Valley.

The upper low slowly ejects inland by Tuesday but a deep marine
layer and onshore flow will likely remain in its wake with
continued trend of below normal temps and onshore breezes.

Some weak ridging or zonal type flow develops Weds afternoon into
Thursday sending temps back to near normal.

Longwave trough approaches by Friday afternoon with onshore winds
and approaching upper low sending inland temps back below normal
once again for Saturday and Sunday of the upcoming Memorial Day
weekend. Latest ecmwf does indicate system may be progressive
with warmer high pressure by Memorial Day Monday but that scenario
may be dubious with developing tropical system in the Gulf of
Mexico potentially slowing the large scale west to east flow
across the US.

&&

.AVIATION...As of 10:36 PM PDT Sunday...Areas MVFR ceilings
tonight into Monday morning. Mid to high clouds with a 500 mb
closed low will slowly move eastward this evening into Monday.

Vicinity of KSFO...MVFR ceiling tonight into Monday morning, a few
more westerly wind gusts to 25 kt this evening. Gusty westerly wind
resumes Monday afternoon and evening.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR ceilings tonight into Monday morning.
Partial clearing possible either by late Monday morning or early
afternoon.

&&

.MARINE...as of 10:32 PM PDT Sunday...Strong and gusty northwesterly
winds will persist over the coastal waters tonight through Monday.
Gusty winds will result in steep wind waves and hazardous conditions
for small crafts. Winds will gradually diminish during the week.
Long period southwesterly swell will mix with northwesterly swell
Monday into Wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm

&&

$$

PUBLIC FORECAST: CW
AVIATION/MARINE: Canepa

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