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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 200439

Area Forecast Discussion
National Weather Service San Francisco Bay Area
939 PM PDT Fri Apr 19 2019

.SYNOPSIS...A pair of upper lows will impact California through
the next 24 hours bringing a cooling/moistening trend, a slight
chance of drizzle along the coast overnight, and increased onshore
flow through tomorrow. A renewed warming trend appears in store 
for the first part of next week.

&& of 9:38 PM PDT Friday...An approaching upper 
level trough, deepening marine layer and increased onshore flow 
resulted in cooler temperatures across the district today. High 
temperatures ranged from the lower to mid 60s at the coast, to the
70s to mid 80s inland. Temperatures were generally 2-12 degrees 
cooler than yesterday, but some near-coastal sites were as many as
17 degrees cooler. The onshore surface pressure gradient has 
tightened to 3.4 mb between SFO and SAC, up from just 0.7 mb 24 
hours ago. Also, the Fort Ord profiler indicates that the marine 
layer has ramped up to nearly 2000 feet. Although there are a lot 
of high and mid-level clouds streaming over northern California, 
IR Satellite imagery does indicate coastal stratus has already 
spread well into inland valleys even now. Updated the short term 
to increase clouds overnight.

The approaching upper level trough will bring another cool day to
the area Saturday, along with possible coastal drizzle developing
later in the day and overnight. High pressure is forecast to begin
edging eastward towards California beginning on Sunday. This will
usher in a warming trend for early next week. A weaker upper
trough is progged to move across northern California later next
week for a slight cool down. 

&& of 7:30 PM PDT Friday...Approaching upper trough 
from the northwest has increased the onshore gradient and deepened
the marine layer. This has brought an early intrusion of cigs to 
the SFO Bay Area. Cigs are IFR initially but should lift into the
MVFR range later tonight as the marine layer continues to deepen.
Cannot rule out patchy drizzle as well early Wednesday morning.

Vicinity of KSFO...IFR cigs lifting to MVFR after 10Z. Possible 
drizzle with reduced vsbys to 5-6 miles after 12Z. Clearing late 
in the morning Saturday with westerly winds gradually increasing 
on Saturday. Gusts to 25-28 kt Saturday afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...An early return of IFR cigs is expected
as stratus covers the MRY Bay. Cigs could come in as early as 02Z. 
Patchy drizzle possible. 

&& of 8:35 PM PDT Friday...Northwest winds will 
increase over the northern and central waters as and near the 
coast today through Saturday as low pressure develops over the 
interior. A moderate northwest swell will also prevail through the


     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 PM




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