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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 231032

Area Forecast Discussion
National Weather Service San Francisco Bay Area
332 AM PDT Tue Apr 23 2019

.SYNOPSIS...Continued warm and dry today with high pressure and
offshore winds in place. A few degrees of cooling possible by
Wednesday but no big changes in the weather pattern. Onshore 
winds return by late in the week and into the weekend with 
temperatures gradually returning to seasonal norms.

&& of 3:32 AM PDT Tuesday...Satellite shows some 
high clouds continuing to spin over the region in anti-cyclonic 
flow aloft as a result of upper level high pressure. Right now 
Half Moon Bay is the only airport reporting some type of clouds 
and reduced vsby with 5 miles and mist with an overcast 300 foot 
cloud deck. Main story for today will be another warm day across 
the Bay Area. Expect widespread readings in the 80s with even some
lower 90s. Closer to the coast and bays comfy 70s will prevail. 
At this time it appears we'll stay a few degrees below record 
levels. The northerly gradient is slowly easing down to 7 mb and 
the decreasing northerly/offshore strength will make it hard to 
get temps to warm into record territory along with the thin cloud 
deck. Anyway, its splitting hairs and those that have been longing
for some warm temperatures will enjoy the heat.

Day to day changes will be subtle away from the coast with only a
few degrees of cooling expected for Weds. This will be due to
offshore winds ending and a more pronounced seabreeze by Weds
afternoon near the coast. The amplified upper pattern and thermal
trough along the coast at the surface can sometimes lead to
southerly wind reversals along the Central Coast. The 00z nam
showed some signs of this around Pt Conception by Weds night but
has since delayed that to Thursday. At this time it appears more
likely that returning northwest winds over the ocean (SST 49-52) 
will allow the marine layer to re-establish by Thursday 
afternoon/evening as the inversion layer deepens with 
strengthening onshore winds near the coast and bays. This is when 
more noted cooling should occur near the coast and then eventually
spread inland later in the week and into the weekend.

Right now the models show a weak upper low approaching Southern
California by Sunday. Some model simulations suggest a slight
chance of showers over the Central Coast but more likely impacting
SLO and Santa Barbara counties. Nonetheless those with outdoor
interests along the Big Sur coast on Sunday will want to follow
the forecast trends for clouds, wind impacts and any possible
precip chances. 

Long range looks dry and seasonable to start next week.


.AVIATION...As of 10:45 PM PDT Monday...for 06Z TAFs. VFR 
conditions and clear skies continue to prevail across the region,
along with light winds. The KACV to KSFO pressure gradient is now
up at a pretty strong 8.5 mb. Consistent with this, latest model 
output and statistical guidance indicate more minimal coastal 
stratus development than earlier runs, with even much of the coast
itself likely to stay mostly clear. Therefore continue to expect 
the San Francisco Bay Area terminals to remain VFR through the 
night and on Tuesday and now the Monterey Bay terminals as well.

Vicinity of KSFO...VFR conditions are forecast to prevail through
the night and on Tuesday. Light winds until the seabreeze return
Tuesday afternoon.

SFO Bridge Approach...Same as KSFO.

Monterey Bay Terminals...VFR conditions are now considered likely 
to prevail through the night and on Tuesday, though can't
completely rule out possibility of brief ceiling development
around sunrise. Light generally offshore winds, turning onshore
early Tuesday afternoon.

&& of 03:02 AM PDT Tuesday...High pressure off the
California coast will shift north. Winds and seas over the
northern waters will remain moderate through  Wednesday night
while lighter winds and seas are expected in the central and
southern waters.


     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 8 AM




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