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

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FXUS66 KMTR 242037

Area Forecast Discussion
National Weather Service San Francisco Bay Area
137 PM PDT Thu May 24 2018

.SYNOPSIS...Cloudy and cool today with increasing chance of
showers tonight into Friday as a late season low passes over the
region. Shower chances end by early Saturday morning. High
pressure builds Sunday through Tuesday with a noted warming and
drying trend.

&& of 1:38 PM PDT Thursday...Overcast conditions
continue to dominate much of the central California coast and San
Francisco Bay Area this early afternoon. The marine stratus
earlier today managed to push well inland to the Santa Clara-
Merced county line at Pacheco Pass, and south through Monterey
County up to the Monterey-Fresno and Monterey-Kings county lines.
The healthy marine layer is responding to an approaching upper
level low that will be the main weather story for our region over
the next day or two as it approaches the California coast.

Temperatures this afternoon will remain rather cool for much of
the area blanketed under the clouds. Highs will be in 50s to 60s
along the coast, and 60s to low 70s for interior locations.
Overnight tonight, the aforementioned upper level low will be
within a few hundred miles of the central California coast. As the
low moves eastward, precipitation chances will increase later
tonight and into the day on Friday. Not expecting a widespread
washout by any means, but more or less scattered shower activity.
In terms of convective thunder potential, models are suggesting
some minimal surface-based and mid-level instability with a
notable downward trend from model run-to-run. The latest Day 2
Storm Prediction Center Convective Outlook has actually backed off
on the general thunder area over parts of the state, which
previously had included parts of the North Bay. It`s still a non-
zero chance, but not looking as likely as earlier. Nonetheless,
the main impacts expected will be wet roadways from the scattered
showers that may impact the Friday commutes. With the scattered
nature of the showers, total rain amounts are expected to remain
light overall with amounts reaching a tenth of an inch or locally
a quarter of an inch for the higher elevations.

Rain chances will begin to diminish overnight Friday and into
Saturday, though can`t rule out lingering showers -- particularly
in the North Bay -- through midday Saturday. Temperatures will
begin rebounding back toward seasonal normals with noticeable
warming for the interior from Saturday to Sunday. Highs will
likely reach the mid 70s to 80s for the interior by Sunday with
additional warming for Monday as a ridge builds over the eastern
Pacific. Can`t rule out the potential for some 90s by Memorial Day
for the interior. Overall it should be a very nice holiday
weekend weather-wise by Sunday and Monday with some clearing even
reaching the beaches. Any beachgoers should always be mindful of
the hazards the Pacific Ocean presents year-round, including the
cold water temperatures and rip current risks. Always be aware of
your surroundings, and never turn your back to the ocean.

As the ridge shifts inland by Tuesday and Wednesday next week,
temperatures will likely begin a gradual cooling trend. By this
time next week models advertise a trough developing over the West
Coast, which would help to reinforce a downward trend in afternoon


.AVIATION...As of 10:39 AM PDT Thursday...Based on latest
satellite trends, webcams and hi-res models forecast will be more
pessimistic than previous forecast. Widespread clouds blanket the
Bay Area with very slow clearing on the edges. Therefore, put
forecast toward an all day event with MVFR cigs. The next
challenge will be any clearing/lifting tonight with approaching
low. Hit or miss showers will develop and impact tonight into
early tomorrow. VCSH for now given uncertainty.

Overall confidence is medium to low.

Vicinity of KSFO...Decided on an all day stratus event. There
could be some lifting above 2500 feet later today, but will keep
at least BKN in forecast. VCSH later today and tonight poss.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR cigs through the period. VCSH poss

&& of 10:33 AM PDT Thursday...Light to locally moderate
winds over the coastal waters today as  high pressure remains off
the immediate coast. The strongest winds today will be located in
the northern San Francisco Bay.  Northwest winds pick up by mid
day tomorrow and become locally  moderate by tomorrow night
through the upcoming weekend. Mixed  seas with a longer period
southwest swell and a smaller northwest  swell. Increasing winds
later this weekend will bring locally  steep fresh swell.


     .Tngt...SCA...SF Bay until 10 PM




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