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

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FXUS66 KMTR 221746

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1046 AM PDT Tue Aug 22 2017

.SYNOPSIS...Dry weather will prevail today with temperatures
near to slightly below normal for the middle of August. Low
clouds and fog will persist in the overnight and early morning
near the coast and in the valleys the next several days. An inland
warming trend is likely late in the week and into the upcoming
weekend due to strengthening high pressure.

&& of 7:49 AM PDT Tuesday...Visible satellite
imagery depicts low clouds blanketing the San Francisco Bay Area
again this morning. The coverage does differ compared to yesterday
morning in that much of the Monterey Bay Area has remained cloud-
free. The mostly clear skies over Monterey and Santa Cruz
Counties have allowed for better cooling this morning compared to
Monday -- at 7 am both Watsonville (KWVI) and Salinas (KSNS) are
running 6 degrees cooler than 24 hours ago. Interior areas with
clouds should transition to mostly clear skies by mid/late
morning. High temperatures for the afternoon will range from the
60s to low 70s along the coast and upper 70s to 90s for inland
locations. Current forecast package remains on track with no
updates planned for this morning. For additional details, please
refer to the previous discussion section.


.PREV of 3:00 AM PDT Tuesday...Unusual satellite
loop this morning which shows mostly clear conditions along the
coast from San Francisco southward while the southern part of SF
Bay down into Santa Clara Valley has clouds. Last hour or so shows
clouds finally expanding and creeping into the Bay while farther
to the south the clouds are advancing very little. For the
Monterey Bay region, the easterly flow around a surface flow is
just enough to keep the clouds away so far although that flow
could end up bringing in clouds from the Hollister and Salinas
Valley -- a very unusual setup! Grids going out right now still
forecast clouds impacting all coastal spots just before sunrise,
however that may be edited before the end of the shift if the
current trends hold.

Anyway, after a busy day yesterday with all of the eclipse news,
today should be much quieter. Synoptically an upper level low will
remain near our CWA through Wednesday night along with a shortwave
trough. This will keep high and low temperatures fairly close
today and tomorrow compared to Monday. Look for 60s to lower 70s
at most coastal spots with 70s and 80s in most inland areas. 90s
will be confined to far inland locations.

The pattern will begin to change starting on Thursday as a ridge
of high pressure off to the east expands toward California. By the
start of the weekend 500 MB heights will exceed 590 DM with values
up to 594 DM possible on Sunday. This will lead to a compressed
marine layer, fewer clouds, and warmer temperatures. Inland
locations will return to the mid 80s to upper 90s with some spots
hitting the lower 100s. With less of a marine influence coastal
towns will hit the 70s and possibly 80s (especially by Sunday).

Longer range guidance suggests very warm to potentially hot
weather next week with the ridge forecast to be the dominant
feature. 850 MB temperatures off the ECMWF at Oakland could hit
up to 27C which places it within 3C of the all time maximum for
the month of August. The GFS has similar values with a peak at


.AVIATION...As of 10:50 AM PDT Tuesday...For 18z TAFs. Surface
high off the Central Coast mitigated impact of overnight marine
layer, with IFR TO MVFR cigs focused primarily over the San
Francisco Bay area. Cigs have retreated offshore/mixed out with
only a few thin layers of stratus left over the Bay Bridge
corridor between downtown San Francisco and Oakland. Look for
breezy afternoon winds and a later return of a shallower marine
layer tonight.

Vicinity of KSFO...VFR today. Light to moderate west winds will
prevail this afternoon, sustained 12-17 kt, with occasional gusts
possible. Borderline IFR-MVFR SCT-BKN late tonight into sunrise

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR today. Surface high offshore kept
marine clouds at bay (in the bay) overnight, however, look for
LIFR to IFR cigs later tonight. Light winds will pick up out of
the west/northwest this afternoon, 9-13 kt.

&& of 10:42 AM PDT Tuesday...Light to moderate winds
through midweek, with locally stronger winds through coastal gaps
during the afternoons. Building high pressure from the west will
bring stronger northerly winds and steep fresh swell. No
significant long period swell through the upcoming week.


     .Tday...SCA...SF Bay from 1 PM




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