Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 291120
Area Forecast Discussion
National Weather Service San Francisco Bay Area
420 AM PDT SUN MAY 29 2016
.SYNOPSIS...Slightly cooler weather is forecast for today,
especially near the coast where there will be areas of low clouds
and fog. A warming trend is then expected for Memorial Day and
Tuesday. Warmer than normal temperatures will continue through the
end of the week. Dry weather will persist.
.DISCUSSION...As of 3:25 AM PDT Sunday...Coastal low clouds and
fog have been gradually developing northward up the coast
overnight. By 3 am fog and low clouds had reached the Golden
Gate. The north-to-south surface pressure gradient from ACV to
SFO has been slowly decreasing since yesterday, but currently
remains relatively robust at 5.8 mb. Thus, there will probably be
limited additional northward development of fog/low clouds by
sunrise...and little inland development from San Francisco Bay is
expected. Farther to the south...low clouds and fog have developed
well inland from Monterey Bay.
Fort Ord profiler data reveals an increase in the depth of the
marine layer from less than 1000 feet to more than 1500 feet over
the past 24 hours. The deeper marine layer, along with a trend
towards stronger onshore flow, will mean cooler weather for our
region today. Afternoon highs will be as much as ten degrees
cooler at the coast, with more modest cooling expected inland.
Sunny conditions will develop in most areas by midday. However,
some coastal spots, mainly south of the Golden Gate, will see only
partial clearing at best.
Warming is expected on Memorial Day and on into Tuesday as an
upper ridge builds over California, compressing the marine layer.
In addition, onshore flow will decrease by Monday. There should be
more widespread afternoon clearing in coastal areas on Memorial
Day. However, a few persistent fog patches can`t be ruled out.
The upper ridge axis is forecast to move to our east by midweek
as an upper trough develops off the west coast along 135W. This
should result in slight cooling on Wednesday and Thursday.
However, temperatures are expected to remain above normal through
the week. And, the models indicate that temperatures will climb
higher once again on Friday as the upper ridge to our east
strengthens. The ECMWF MOS indicates the most pronounced warming
late in the week, with SFO forecast to reach 82 on Friday and
The models agree that a weak upper low will develop off the
southern California coast late in the week and then lift gradually
to the northeast next weekend. The GFS forecasts precip across the
southeast portion of our forecast area by Saturday morning as the
low approaches. The ECMWF maintains dry conditions in all areas
until the following Monday night. Given these model differences
and the fact that this precipitation potential is still out at
day seven and beyond, will hold off on adding any explicit mention
of shower chances to the forecast just yet.
.AVIATION...as of 04:15 AM PDT Sunday...The northerly gradient is
weakening and loosing the battle with the southerly clouds.
Latest satellite imagery shows a low stratus decks charging up the
coast. With the exception of MRY Bay the question is how much of
the stratus deck makes it inland? Latest short range models
suggest a possible intrusion later this morning, but conf is low.
Will allow for some intrusion, but keep it short lived. VFR this
afternoon, but cigs return tonight.
Vicinity of KSFO...Conf is low for any cigs in SF Bay. However,
will forecast a few hours of MVFR cigs and KOAK and a tempo cigs
at KSFO. VFR after 17-18z. Cigs return tonight. after 12Z
possibly later. Confidence is not high as stratus could stay out
SFO Bridge Approach...less likely for any cigs in the short term.
Monterey Bay Terminals...MVFR/IFR through 18-19z...vfr this
afternoon. cigs return early tonight.
.MARINE...as of 2:19 am PDT Sunday...High pressure over the
eastern Pacific and low pressure inland will result in gusty
northerly winds today and tonight. Winds will be strongest over
the outer waters, especially north of Point Reyes. Winds will
gradually decrease on Memorial Day with weakening high pressure. A
building southerly swell is anticipated to arrive late Monday into
.Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...SF Bay from 12 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
PUBLIC FORECAST: Dykema
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