NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 222013

Area Forecast Discussion
National Weather Service San Francisco Bay Area
113 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 10:26 AM PDT Monday...For 18z tafs. Shallow
marine layer is eroding back to the coast as 18Z tafs become
valid. VFR at all terminals this afternoon with breezy sea breeze
conditions this afternoon. Shallow marine layer will return
tonight with fog possible.

Vicinity of KSFO...VFR through early tonight. Based on latest
model guidance and what happened this morning will bring low
clouds back into SF Bay. The low confidence area will once again
be SFO itself. Went with a pessimistic forecast tonight with a few
hours of clouds/fog tomorrow before a quick burn off.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR this afternoon. Cigs return this
evening with IFR to LIFR conditions possible.

&& of 10:23 AM PDT Monday...High pressure building over
the Pacific Northwest will maintain light to moderate
northwesterly winds through midweek. Winds will increase midweek
as a thermal trough develops along the coast tightening the
pressure gradients over the northern outer waters. Strongest winds
are expected over the outer waters while the inner waters remain
mostly light.


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




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NWS MTR Office Area Forecast Discussion