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

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FXUS66 KMTR 230528

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1028 PM PDT Mon May 22 2017

.SYNOPSIS...Look for cooler conditions through most of the week as
a onshore flow combines with the marine layer. Minor warming is
then expected during the upcoming weekend especially for inland

&& of 9:00 PM PDT Monday...No forecast updates
planned for this evening with about a 1500 foot marine layer in
place along the immediate coast. Low clouds making their way
through the Golden Gate and into the Berkeley hill as well as
spreading inland around the Monterey Bay region. Inland areas that
reached the 90s today will see more significant cooling for
Tuesday as onshore flow continues to increase with a deepening
marine layer in response to upper troughing aloft.

All available mos data suggests continued cooling trend through
midweek for inland areas with robust onshore winds in place and
likely persistent stratus around the coast and bays. The trend
will be for near or below normal temperatures for much of the rest
of the work week.

Looking ahead to the long holiday weekend, long range models
suggest a seasonable weather pattern with dry and near normal


.PREV DISCUSSION...As of 1:15 PM PDT Monday...As expected temperatures
are running cooler for all locations away from the coast today
with many spots 5 to 12 degrees less than values from Sunday.
Current readings show a wide range from 50s and 60s to parts of
the coast with 70s and 80s inland. Still a few hours of heating,
so would expect the warmest inland spots to again get into the
90s, however the number of locations should be less than
yesterday. Satellite shows widespread clouds along the water and
with the minor onshore flow expected to continue, likely that many
of the local beaches will see little to no sunshine today.
Tonight will be a near repeat of last night with patchy fog along
the coast and to some inland spots. Lows will mostly be in the 50s
with 60s above 1500 feet.

Synoptically the ridge of high pressure in charge will begin to
flatten out through the week as a system dives down from Canada
and works into the Northern Rockies. 500 MB heights will drop from
587 DM today to 573 DM by Thursday. Inland locations that have
been in the 90s the past few days will drop back into the upper
60s to the lower 70s. Closer to the coast widespread mid 50s to
mid 60s can be expected. With the onshore flow in place, much of
the week could by quite grey at the coast.

Longer range guidance shows the ridge trying to rebuild by the
weekend although heights will be less than the past few days. By
Sunday inland spots will be back in the mid 70s to mid 80s away
from the coast with 60s to mid 70s near the water.


.AVIATION...As of 10:27 PM PDT Monday...Stratus and fog are
heavily blanketing the immediate coast with some stratus and fog
reaching through the Golden Gate this evening; IFR cigs and vsbys
are forecast to continue in these areas tonight and Tuesday morning.

The marine layer depth ranges from approx 1,000 feet Bay Area to
1,500 north Central Coast. 925 mb temperatures remain nearly
unchanged over the Bay Area and cool less than 1C over the Central
Coast tonight thus the marine layer depth should remain nearly
unchanged overnight, possibly including Tuesday as well.

Gusty onshore winds are likely over the San Francisco bays Tuesday
afternoon and evening, similarly gusty winds are expected again
Wednesday. Lower level cooling will become more robust by this
time Tuesday evening through Wednesday thus the marine layer depth
should increase and stratus and fog intrusion should then really
get underway.

A little more than moderate confidence VFR persists for most of the
Bay Area terminals tonight with exception of southerly flow bringing
LIFR/VLIFR cigs and vsbys to KSTS late tonight and Tuesday morning.
For Monterey Bay Area IFR/LIFR will continue into Tuesday morning.

Vicinity of KSFO...VFR. W-NW winds 5-10 knots tonight, becoming gusty
from the W-NW Tuesday afternoon and evening.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...IFR/LIFR prevails tonight into late Tuesday
morning. VFR returns late Tuesday morning and afternoon, onshore winds
will likely bring stratus and fog back in Tuesday evening.

&& of 9:45 PM PDT Monday...Surface high pressure over
the eastern Pacific will strengthen from tonight into Wednesday
morning keeping northwesterly winds going over the outer waters. A
surface ridge of high pressure over the Central Coast will cause
winds over the inner coastal waters to be primarily light
southwesterly through Tuesday. Except for the Monterey Bay onshore
winds will be gusty over the bays each afternoon and evening at
least through mid-week.






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