Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 270454
Area Forecast Discussion
National Weather Service San Francisco Bay Area
954 PM PDT THU MAY 26 2016
.SYNOPSIS...Continued building of a ridge of high pressure along
the coast, along with low level flow progressively turning more
offshore, will result in a warming trend through Saturday.
Then for the latter part of the holiday weekend, a cooling trend
appears to be in store as the marine layer and coastal stratus
redevelop. For next week, temperatures are projected to remain
above seasonal norms inland but vary from day-to-day closer to
the coast as passing weak upper level disturbances modulate the
marine layer depth and onshore flow. Aside from possible local
coastal drizzle, dry weather conditions are expected to prevail
through the forecast period.
.DISCUSSION...As of 09:15 PM PDT Thursday...Skies are mostly
clear across the district, aside from some areas of low cloudiness
over the coast and coastal slopes of San Mateo County, and in the
southern Monterey Bay region. Some afternoon cumulus did develop
over the higher terrain of northeastern Santa Clara County and
southern San Benito County, but not to the point of producing any
showers. Although a few spots on the immediate coast were actually
a tad cooler than yesterday (the high this afternoon at Half Moon
Bay was 61 today compared with 63 yesterday for example), more
inland areas generally warmed up around 4-8 degrees.
The coastal stratus is expected to fill back in and extend locally
inland overnight, though somewhat less extensively than last
night especially north of the Golden Gate. Have noted that the
north-south pressure gradient from KACV to KSFO has increased to
5.6 mb (04Z) from 3.3 mb 24 hours ago, while new NAM and local
high-res wrf model boundary layer relative humidity output continue
to restrict overnight increases over our more northern coastal
areas. Then Friday night into Saturday morning, skies look to
remain mostly clear even by the beaches, aside perhaps from some
patchy low clouds along the San Mateo County coast and in the
vicinity of the Monterey Peninsula.
The forecasted warming trend in daytime temperatures through
Saturday remains on-track. Latest model runs show continued warming
of the air mass aloft, with low-level flow first weakening out of
the west and then turning more offshore as we head into the start
of the weekend.
For Sunday and Monday, latest NAM model output indicates
progressive redevelopment of the marine layer and night and
morning coastal stratus will occur, with low cloudiness
potentially extending inland through the bays by Monday morning.
The air mass aloft however is projected to remain warm. The net
result then looks to be a cooling trend primarily areas closer to
the water beginning on Sunday, and then all but farther-inland
locations on Memorial Day. But at the latter it should remain
In the extended, temperatures are projected to remain above
seasonal norms inland, but vary somewhat from day-to-day closer
to the coast as passing weak upper level disturbances modulate the
marine layer depth and onshore flow. High confidence that it will
remain dry through the forecast period aside from the possibility
of some local coastal drizzle.
.AVIATION...as of 9:54 PM PDT Thursday...Northerly gradients are
steepening as high pressure builds over NorCal. The ACV to SFO
gradient is 5.6 mb and forecast to strengthen into Friday. Stratus
clouds will gradually redevelop tonight with onshore winds favoring
areas of stratus/fog intrusion tonight.
Vicinity of KSFO...Tempo MVFR cig 07Z-10Z followed by MVFR cig
prevailing 10Z-15Z Friday. Early return to VFR is likely Friday.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...MVFR cigs gradually transitioning to IFR
cigs tonight. Stratus may persist near the Monterey Bay Peninsula
Friday, low confidence on clearing timing.
.MARINE...as of 9:12 PM PDT Thursday...High pressure will persist
over the eastern Pacific and northern California through Friday
resulting in strong and gusty northwest winds particularly over
the northern waters. Over the Memorial Day Weekend this high
pressure center will gradually weaken. Northwest winds will
continue early next week but are not expected to be quite as
.Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
GLW...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
SCA...Rough Bar Advisory for SF Bar
SCA...SF Bay until 11 PM
PUBLIC FORECAST: Blier
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