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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 162336

Area Forecast Discussion
National Weather Service San Francisco Bay Area
436 PM PDT Sun Jun 16 2019

.SYNOPSIS...A few degrees of warming is expected for mainly inland
areas on Sunday as high pressure begins to build near the West 
Coast. More widespread and significant warming is forecast for 
Monday and Tuesday as high pressure strengthens and onshore flow 
weakens. However, warming at coastal areas will be limited due to
persistent onshore winds. Seasonable temperatures, along with 
areas of night and morning low clouds, are forecast through the 
end of next week.

&& of 01:30 PM PDT Sunday...Morning low clouds and 
patchy fog/drizzle did finally roll back to the coast this 
afternoon. However, as predicted coastal area will see little in 
the way of sunshine this afternoon as clouds linger. Needless to 
say, interior portions are much warmer than the immediate coast. 

The longwave pattern indicates a weak shortwave trough passing
overhead, the likely culprit for the deep marine layer and morning
drizzle. In its wake, high pressure currently upstream will
continue to build over the region later tonight and more so on
Monday. The building high pressure will help to compress the
marine layer the next few nights, but nothing to completely mix it
out. Inland areas will see a gradual warming due to the compressed
marine layer, warmer airmass at 850mb and building 500mb
heights. One component missing to make this a real warm up is
offshore flow (northeast winds in the low levels). Interesting to
note that 850mb temperatures will be just as warm if not warmer
than the most recent heat wave. Persistent onshore flow will be 
the main limiting factor for heat this week. Simply put, night and
morning clouds will continue with a warming trend peaking interior
on Tuesday. Adequate cooling/relief at night will really limit
heat risk concerns. Highs will peak across the interior in the
upper 80s to near 100. 

Temperatures will hold steady or drop a few degrees on Wednesday
as the ridge of high pressure weakens. More widespread cooling is
expected by Thursday/Friday as a trough pivots through the PacNW. 

&& of 4:305PM PDT Sunday...Marine layer continues 
around 2000 feet but is expected to compress overnight. Onshore 
gradient has turned more northwest as the SFO-ACV pressure 
gradient has increased to 4.2 mb. This will result in a later 
intrusion of clouds into the Bay Area. Latest tafs have backed off
the timing of the low cigs for a couple of hours. Cloud bases are
expected to be lower tonight. 

Vicinity of KSFO...IFR cigs after 06Z with bases 800-1000 feet. 
West winds 15-18 kt decreasing after 04Z. 

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Widespread MVFR cigs after 02Z lowering
to IFR after 05Z. 

&& of 04:22 PM PDT Sunday...Breezy northwest winds
across most of the waters today, with locally stronger, gusty
winds across the outer waters north of Point Reyes and through the
Golden Gate gap to Angel Island.  Steep fresh northwest seas.


     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...SF Bay until 8 PM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm




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