Technical NOAA Weather Discussion

FXUS66 KMTR 210554

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1051 PM PDT Mon Aug 20 2018

.SYNOPSIS...An upper level trough pushing through the Pacific 
Northwest will dig southward result in a cooling trend through 
Tuesday. Temperatures then rebound to near seasonal averages for the 
remainder of the week with periods of night and morning clouds along 
the coast and into the valleys. 

&& of 9:14 PM PDT Monday...Infrared satellite 
imagery shows increasing low cloud coverage across much of the 
central California coast and parts of the San Francisco Bay Area 
this evening. The San Francisco and Oakland Airports are already 
reporting broken skies as the 2000+ ft marine layer continues to 
push clouds inland. The upward trend in the marine layer depth is 
in response to an upper level low that presently centered near 
central Idaho. In addition to the deeper marine layer, this upper 
low brought the start of a cooling trend to the region this 
afternoon. Highs across the interior were noticeably cooler:
Concord Airport, for example, was 10 degrees cooler this afternoon
compared to Sunday (83 vs 93). This downward trend is expected to
continue into Wednesday with another few to several degrees of 
cooling for the interior. No major updates planned for this 
evening; for additional details beyond the next 24 hours, please 
refer to the previous discussion.


.PREV of 1:49 PM PDT Monday.... Satellite imagery
shows most of this morning's stratus has retreated back to the 
coast, aside from some lingering low clouds around the Monterey 
Bay. Temperatures across the region are generally around 5 degrees
cooler than this time yesterday. Expect some additional warming 
this afternoon. The marine layer has deepened to around 1800 to 
2000 ft per the Bodega Bay and Fort Ord profilers as an upper 
trough moves through the Pacific Northwest. 

As the aforementioned trough digs a little further south through 
tomorrow, additional cooling across the region is forecast along 
with another round of widespread overnight and morning low clouds.
With a deeper marine layer, expect patchy fog and coastal drizzle
to continue as well. Afternoon highs tomorrow will be around 5 degrees
below normal translating to the upper 50s and 60s along the coast
and low 80s to low 90s inland. A gradual warming trend will then 
begin by Wednesday as the upper trough shifts northward allowing 
the ridge over the desert southwest to strengthen. A broad upper 
trough over British Columbia and an upper low to the west of 
California will keep the ridge of high pressure from being the 
dominant weather feature. This will keep temperature increases 
this week relatively modest. Highs along the coast late this week
will remain mainly in the 60s to low 70s with 80s and 90s across 
the interior. CPC's 6-10 and even 8-14 day Outlook continue to 
show temperatures near seasonal averages through the end of the 

&& of 10:51 PM PDT Monday...Widespread ocean based 
stratus, a deeper marine layer and onshore winds will usher IFR 
including patchy VLIFR stratus ceilings and fog inland tonight 
into Tuesday morning. Recent high resolution model output still 
leaning toward increasing wildfire smoke arriving from western 
CONUS and Canadian wildfires tonight through mid-week resulting in
decreasing surface and slant range visibilities.

Vicinity of KSFO...Onshore winds will usher in borderline MVFR/IFR
cigs tonight with slantwise vsby issues this week. 

SFO Bridge Approach...Moderate to poor slant range visibility for
the period. Otherwise similar to KSFO.

Monterey Bay Terminals...Stratus ceilings gradually lowering to IFR
overnight. Expect reduced slant range and horizontal vsbys this

&& of 9:42 PM PDT Monday...Generally lighter northwesterly
winds across the coastal waters through midweek then increasing winds
mainly over the northern waters by late week and weekend.





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Prepared by Weather at: Tue Aug 21 02:30:02 PDT 2018
From the National Weather Service