Technical NOAA Weather Discussion

FXUS66 KMTR 230034

Area Forecast Discussion
National Weather Service San Francisco Bay Area
534 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


.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 5:34 PM PDT Monday...The marine layer depth
varies from 700 feet over the Bay Area to 1200 feet over the north
Central Coast late this afternoon. The SMX-SFO gradient is 2.3
mb; at present as well as tonight into Tuesday the NAM forecasts a
neutral gradient, applying a 2 mb correction a southerly component
to the coastal winds is likely to continue into Tuesday. The SFO-
SAC gradient is 2 mb which is line with the NAM, which predicts
stronger onshore gradient/wind developing Tuesday afternoon and
evening with SFO-SAC gradient near 4 mb, similarly a moderate to
strong gradient and wind develops again Wednesday.

00z tafs for the Bay Area indicate VFR except southerly flow will
likely bring LIFR/VLIFR cigs and vsbys to KSTS late tonight and
Tuesday morning. Also, for Monterey Bay Area IFR/LIFR is likely
to develop this evening. Moderate to high forecast confidence.

Vicinity of KSFO...VFR. W-NW winds with occasional gusts to 20-25
knots til 05z this evening. Gusty W-NW winds resume Tuesday afternoon
and evening.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR then tempo IFR/LIFR 02z-07z then IFR/LIFR
prevailing tonight into late Tuesday morning. VFR returns late Tuesday
morning and afternoon, onshore winds will likely bring stratus and
fog back Tuesday evening.

&& of 5:13 PM PDT Monday...Northerly flow will persist
with light to moderate winds and small seas. High pressure will
strengthen north of the region increasing winds midweek. Winds
will be strongest north of Point Reyes, especially the outer


     .Tngt...SCA...SF Bay until 9 PM




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Prepared by Weather at: Mon May 22 18:30:04 PDT 2017
From the National Weather Service