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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 231736

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1036 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 8:24 AM PDT Tuesday...Visible satellite 
imagery reveals mostly clear skies dominating the San Francisco 
Bay Area and Central California Coast this Tuesday morning as a 
upper level ridge axis sits over the northern half of the Golden 
State. Aside a few passing high clouds, these mostly clear skies 
will continue through the afternoon hours. Temperatures across the
region are already running a good 5-10 (or more) degrees warmer 
than they were this time 24 hours ago...both Napa and Oakland 
Airports are 11 degrees warmer than this time yesterday; 8 degrees
warmer at San Francisco and Livermore Airports; and 7 degrees 
warmer at Hayward, Concord, Moffett Field, and San Jose. This 
trend will continue through the day as temperatures warm to the 
70s along the coast and widespread 80s for inland communities, 
equating to about 10 to 20 degrees above middle to late April 
climatological normals. Can't rule out an isolated 90 degree 
reading for some far interior locations. The short-term forecast 
package is on track and don't anticipate a morning update. For 
additional forecast details, please refer to the previous 
discussion section.


.PREV 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 10:35 AM PDT Tuesday...VFR. Other than FEW/SCT
high clouds streaming over the northern portion of the region this
morning, VFR conditions will prevail. Forecast models do show an
increase in low level moisture and development of low stratus 
over the Monterey Bay terminals and even over the North Bay early
Wednesday morning. However, confidence of occurrence is low for 
the North Bay and moderate for the Monterey Bay terminals. 

Vicinity of KSFO...VFR. 

SFO Bridge Approach...Same as KSFO.

Monterey Bay Terminals...VFR. Potential for low clouds to develop
around 12 Z Wednesday. Moderate confidence.

&& of 9:36 AM PDT Tuesday...High pressure off of the 
California coast will slowly shift northward today. Winds over the
northern waters will remain moderate and gusty resulting in 
steep, short-period swell. Elsewhere, winds will be locally gusty 
at times in the afternoon and evening hours yet weaker overall.


     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm




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