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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 281156

Area Forecast Discussion
National Weather Service San Francisco Bay Area
456 AM PDT Fri Jul 28 2017

.SYNOPSIS...Slightly cooler temperatures are forecast for today 
and Saturday as a weak upper trough approaches the northern 
California coast. Even so, most inland areas will remain warm. A 
gradual warming trend is then forecast from Sunday through much of
next week as a high pressure ridge strengthens over the western 
United States. Thus, expect a prolonged period of very warm 
temperatures inland. Mild conditions will persist near the coast. 


.DISCUSSION...As of 3:15 AM PDT Friday...Satellite imagery shows
less inland low cloud coverage compared to 24 hours ago although
stratus is extending well down the Salinas valley at this time. 
The marine layer depth is more shallow - around 1000 feet deep per
the Fort Ord profiler, and surface pressure gradients are about 
the same onshore with 2.3 mb from SFO to SAC, but much stronger 
from north-to-south with 5.4 mb from ACV to SFO. This type of 
gradient pattern lends itself to more clouds pushing into the 
Monterey Bay and Salinas Valley and fewer clouds working into the 
San Francisco Bay. 

Meanwhile, a weak upper level trough is forecast to approach the 
coast today which is expected to deepen the marine layer a little 
today and tomorrow. Inland locations are expected to see similar 
warmth to yesterday, with plenty of upper 80s and 90s for highs
today. Near-coastal areas could see a couple of degrees of 
cooling depending on the strength of the sea breeze this 
afternoon. Saturday is expected to be slightly cooler as the weak 
trough moves through. 

A strong ridge of high pressure currently centered over the Rocky
Mountain states will build and gradually shift to the west
beginning on Sunday and through the coming week. This will bring
warmer temperatures to the district through the remainder of the
forecast period. The ridge is progged to strengthen during the
latter part of next week for very warm to hot temperatures
across inland areas. 


.AVIATION...as of 4:56 AM PDT Friday...For 12z tafs. Low clouds
have filled in along the coast this morning. A shallow marine 
layer around 800 ft will keep low clouds confined to the coast and
terminals mainly cloud free with the exception of Monterey Bay
terminals. Light westerly flow will ramp up this afternoon. 

Vicinity of KSFO...VFR conditions will prevail. Light to moderate
westerly winds expected to ramp up to 15 to 20 kt this afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...LIFR cigs expected through the morning
hours with low clouds expected to scatter out around 16z. Light 


.MARINE...as of 2:38 AM PDT Friday...Moderate to locally strong 
northwesterly winds will continue through the end of the week 
across the northern waters. Gusty winds will produce steep wind 
waves and fresh swell. Two tropical systems in the Pacific will 
produce a long period southerly swell to arrive over the weekend. 
Interaction between the northwesterly wind waves and southerly 
swell will create choppy conditions across the waters.


     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm




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