Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 270355
Area Forecast Discussion
National Weather Service San Francisco Bay Area
855 PM PDT FRI AUG 26 2016
.SYNOPSIS...Very little change is expected to occur through the
weekend and through the middle of next week. Temperatures will be
near or slightly below normal through the period. Areas of night
and morning low clouds will give way to sunny skies by midday for
inland areas. Most coastal areas will continue to see widespread
low cloud cover persist through the daytime hours.
.DISCUSSION...As of 8:55 PM PDT Friday...The marine layer
deepened to nearly 3000 feet today and winds turned light
southerly near the coast. These developments resulted in cooler
daytime temperatures today across Santa Cruz County, across much
of the North Bay, as well as portions of the East Bay and southern
Santa Clara Valley. Santa Rosa Airport`s high of 72 today was 12
degrees below normal. Ben Lomond had a high of only 67 (14 degrees
cooler than yesterday`s 81).
Temperatures are forecast to gradually increase in most areas
through the weekend as an upper level shortwave ridge develops
over California, compressing the marine layer. But for the most
part, temperatures will remain at least slightly cooler than
normal through the weekend. In addition, southerly winds along
the coast will slowly swing around the west by Sunday and then to
the northwest by Monday. This change in winds direction will allow
those areas that cooled by a significant amount today to warm back
up close to normal by early next week.
The models agree that an upper level trough will gradually deepen
along the West Coast next week. This will keep our temperatures on
the cool side of average through the week. In addition, the
trough may deepen sufficiently by the middle of next week to mix
out the marine layer which will mean clearing of low clouds in
coastal areas, something we`ve seen very little of during August.
Beyond the middle of next week the models begin to diverge. The
18Z GFS continues to deepen the upper trough over California
while the 12Z ECMWF moves the trough axis off to our east. If the
GFS were to verify, inland temperatures would cool well below
normal late next week and into the first weekend of September and
we could even see some light rain that weekend. The ECMWF solution
would hold temps relatively steady during this time period and
maintain dry conditions. Due to these model differences, forecast
confidence decreases significantly by late next week.
.AVIATION...as of 10:48 AM PDT Friday...Low clouds quickly
dissipating over inland areas around the San Francisco Bay with
generally weak southerly winds. Cloud cover slower to burn-off
over the North Bay however. Meanwhile, low clouds persist over
much of the Monterey Bay Region as the marine layer remains around
2800 feet in depth. Thus, this area may remain under low clouds
through much of the day, potentially breaking out for a few hours
this afternoon. Onshore flow will increase slightly though
the afternoon and early evening with low clouds likely to spread
back inland late this evening and persist into Saturday morning.
Vicinity of KSFO...Low ceilings have scattered out over the
region this morning with variable to light southerly winds. Wind
speeds will then increase this afternoon out of the west/southwest
with the onset of the sea breeze. Low clouds likely to return
around 04Z this evening and will persist into Saturday morning.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...MVFR ceilings persist over the region
this morning and will likely remain in place through much of the
day. However, inland areas such as KSNS may scatter out briefly
this afternoon before low clouds spread back inland this evening.
Onshore winds will increase slightly through the afternoon as the
sea breeze develops.
.MARINE...as of 10:48 AM PDT Friday...A weak surface pressure
gradient across the coastal waters will maintain generally light
winds and seas through the weekend. Locally stronger and gusty
winds anticipated north of the Bay Bridge in the afternoon hours.
A mixed short period northwest swell and a long period southerly
swell will continue to impact the coastal waters.
.Tngt...SCA...SF Bay until 11 PM
PUBLIC FORECAST: Dykema
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