Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 300959 CCA
Area Forecast Discussion
National Weather Service San Francisco Bay Area
253 AM PDT Thu Mar 30 2017
.SYNOPSIS...Cooler and breezy conditions are forecast for
today in the wake of a cold frontal system. Most locations will
not receive measurable rainfall from this dry system. Locally
strong and gusty northwest winds are likely from Thursday
afternoon into Friday. A warming trend is then expected for the
upcoming weekend as high pressure rebuilds over the region.
.DISCUSSION...As of 2:55 AM PDT Thursday...Satellite imagery shows
a weak, dry cold front entering the state over northwest
California preceded by a discontinuous cloud bank early this
morning. The cloud decks ahead of the frontal boundary range from
the lower levels well ahead of the front (with several weather
stations reporting ceilings at 800 feet or lower), up to around
15000 feet further upstream. At this time, no precipitation has
been observed as this system advances into the local region, with
only light precipitation observed further north up the California
coast. Only minimal to trace amounts of precipitation are
expected locally as this systems moves across the area, with all
short term models showing dwindling chances of rain after sunrise.
This system will result in much cooler temperatures today, with
temperatures generally 5 to 10 degrees cooler than yesterday. This
cooling comes from a combination of increased onshore flow, cold air
advection, and decreased insolation from the varying cloud decks.
The NW-SE pressure gradient will tighten in the wake of this
system as it exits into southern California and high pressure
builds off the northern California coast. This will result in
increasing northwest winds in the wake of the aforementioned
system. The strongest winds will occur along the coastline, which
will begin to ramp up later this morning behind the front, then
strengthen later this afternoon into early this evening, before
subsiding tonight. The strongest winds will then shift to the
higher inland terrain later tonight through midday tomorrow. As a
result, a wind advisory is now in effect for the coast through 8pm
tonight, and midday friday for the higher inland terrain. Local
wind gusts up to 45mph are expected by later tomorrow, with gusts
exceeding 50mph possible over the higher inland terrain through
midday tomorrow. Winds will then subside into Saturday, where
locally breezy conditions are expected to persist.
The air mass is expected to dry out into Friday, allowing for peak
diurnal heating, and a rapid warmup through the end of the week as
a ridge of high pressure builds inland. Expect to see temperatures
rise further into Saturday as the ridge shifts inland. The ridge
weakens later into the weekend, leading to near normal seasonal
By early next week, another dry, breezy system for the region
will slide into California from the northwest and descend into the
Great Basin. High pressure then builds into the region through mid
week, bringing warmer, drier conditions. Longer range models show
a deeper storm system well to the northwest late next week,
however, there are vast differences in the trajectory. For now,
this stronger system looks more like a Pacific Northwest event,
however, it is far enough out in the extended period that the
forecast models may cause it to drift southward over the coming
days. Stay tuned for the latest info!
.AVIATION...as of 10:52 PM PDT Wednesday...Coastal stratus and
fog with a combination of IFR and MVFR cigs reported this evening.
Primarily expecting an onshore wind flow tonight along with
pockets of light rain or drizzle developing. A cold front moves
through late tonight and Thursday morning first lifting then
eventually eroding the marine inversion followed by a steepening
northerly gradient and winds Thursday into Friday. VFR is likely
to return by mid-late Thursday morning, strong and gusty NW winds
coastal waters with some overlap onto land developing Thursday
afternoon and evening.
Vicinity of KSFO...MVFR cig developing tonight then lowering to
IFR cig in light drizzle or rain tonight with W-NW winds. Clearing
to VFR by 17z Thursday, strong and gusty W-NW winds Thursday
afternoon and evening.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...MVFR/IFR developing tonight with light
drizzle or rain developing later tonight into Thursday morning.
VFR forecast to return by late Thursday morning, strong and gusty
W-NW winds Thursday afternoon and evening.
.MARINE...as of 10:29 PM PDT Wednesday...Gusty northwest winds
will accompany a cold frontal passage later tonight through
Thursday morning. Surface high pressure will build over far
northern California Thursday into Friday resulting in gale force
winds over the coastal waters beginning later Thursday and continuing
into Friday. Northwest swell will level off while swell periods
steadily decrease tonight through Thursday. Large very long period
northwesterly swell will move into the coastal waters Saturday
evening into Sunday.
.Tday...Wind Advisory...Coastal Areas 12PM THU to 8PM THU.
Inland elevated terrain 12AM FRI
until 12PM FRI.
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
GLW...Pt Arena to Pt Reyes 0-10 nm from 5 PM
GLW...Pt Reyes to Pigeon Pt 0-10 nm from 5 PM
GLW...Pigeon Pt to Pt Pinos 0-10 nm from 5 PM
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm from 5 PM
GLW...Pt Arena to Pigeon Pt 10-60 nm from 5 PM
GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 5 PM
SCA...Rough Bar Advisory for SF Bar until 3 PM
SCA...SF Bay from 3 PM
SCA...Mry Bay until 3 AM
SCA...Mry Bay from 2 PM
PUBLIC FORECAST: DRP
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