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FXUS66 KMTR 240322

Area Forecast Discussion
National Weather Service San Francisco Bay Area
822 PM PDT Tue May 23 2017

.SYNOPSIS...An inland cooling trend will continue through late week 
as high pressure weakens and the marine influence increases. Minor 
warming is then expected during the upcoming weekend as high 
pressure returns to the West Coast.

&& of 08:20 PM PDT Tuesday...Only minor adjustments
made to sky cover based on current trends. As of 7:50 pm PDT, 
visible satellite showed an extensive area of low clouds off the 
coast and impacting parts of the Bay Area with the clouds 
intruding through the Golden Gate east to Berkeley. Fort Ord 
profiler shows the marine layer around 1,500 ft this evening.

Tuesday was another warm day for inland locations with highs ranging
from the 80s to low 90s. Don't expect to see any 90s tomorrow as 
the ridge responsible for bringing the well above normal 
temperatures continues to push east into the continent. Most 
inland locations can expect to see temperatures about 5 to 10 
degrees cooler on Wednesday. Additional cooling will occur from 
Wednesday to Thursday as an upper level low centered over 
southwestern Canada allows for 500 mb heights to continue to fall 
over the region. High temperatures by Thursday will fall to the 
upper 60s to mid 70s across the East Bay and South Bay, as well as
the Salinas Valley. Coastal locations can expect widespread 
middle 50s to middle 60s with marine stratus.

Models suggest another ridge to build over the West Coast in time
for the holiday weekend, though at this point it doesn't look that
it'll be as warm as it was over the past few days. Temperatures
should be at or within several degrees of climatological normals
for the end of May.


.PREV of 01:32 PM PDT Tuesday...Low clouds continue to
hug the coast this afternoon with mostly sunny skies inland. With
this, the warmest temperatures persist over inland areas while 
cooler temperatures (generally in the upper 50s to lower 60s) are 
common at the coast. This trend will likely persist into tomorrow,
with low clouds spreading inland this evening and into the 
overnight hours with a marine layer of around 1500 feet in place. 
However, as the ridge aloft weakens and onshore flow increases, 
inland locations will see the gradual cooling trend continue into 
Wednesday. With the deepening marine layer, cannot rule out patchy
coastal drizzle/mist during the late night and early morning. 
However, measurable precipitation is highly unlikely.

Further cooling is expected late in the week as the ridge flattens 
and an upper level low drops down into the northern Rockies. With 
this and an increase marine influence, looks for temperatures to 
fall below seasonal averages for just about all inland locations. 
More widespread 60s and 70s will be likely during the afternoon hours 
beginning on Thursday and continuing through Saturday. 

By late in the weekend and into early next week, a ridge of high 
pressure is currently forecast to rebuild over the West Coast. This 
would likely result in a slight warming trend with afternoon 
temperatures back to near seasonal averages. In addition, look for 
mostly sunny afternoon conditions inland while coastal clouds will 
be possible. 


.AVIATION...As of 5:17 PM PDT Tuesday...The marine layer is 
deepening with a decent onshore push of stratus and fog expected 
this evening into Wednesday morning. Timing stratus cigs will be
challenging due to a southerly component to the wind over the
inner coastal waters this evening. Additionally a lower level 
cyclonic circulation over the offshore waters advances eastward 
reaching the coastal waters just west of the Bay Area Wednesday. 

Ongoing area-wide surface to lower level cooling thus expected to 
couple with a strengthening southerly gradient (SMX-SFO presently
1.7 mb) and a southerly wind component will likely become more of
an influence on the marine layer from later tonight into Wednesday.
Surface pressures will generally be highest over the Central Coast
and lowest over far northern California through Wednesday favoring
a continuation of the SMX-SFO gradient nearing 4 mb tonight and 
Wednesday per latest NAM model output.

Vicinity of KSFO...Low to moderate confidence VFR holds this evening
which is highly dependent on wind direction and strength as well as
the marine layer depth; presently San Carlos sodar shows it's near
1,000 feet deep. As long as the marine layer depth holds and the 
wind does not become more due westerly VFR should hold for a while
longer this evening. IFR is forecast, but not til much later tonight
with general trend toward MVFR cig early Wednesday morning. Gusty
W-SW winds likely Wednesday late morning and afternoon.

SFO Bridge Approach...Similar to KSFO. 

Monterey Bay Terminals...MVFR cigs trending to IFR this evening
the possibly back to MVFR cigs late tonight and Wednesday morning.
Low confidence VFR redevelops by afternoon Wednesday.

&& of 4:42 PM PDT Tuesday...Light winds will to continue
tonight across the waters. Split flow tomorrow expected with 
increasing northerly winds over the northern outer waters and 
increasing southerly winds along the coast. Winds are forecast to
weaken late this week.


     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm from 9 PM
             SCA...SF Bay until 9 PM




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