Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 292057
Area Forecast Discussion
National Weather Service San Francisco Bay Area
157 PM PDT Wed Mar 29 2017
.SYNOPSIS...Cooler and breezy conditions return to the region
on Thursday as a cold front sweeps through overnight. This system
will result in a chance of very light precipitation from late
tonight into early Thursday morning, however most locations will
not receive measurable rainfall. Breezy to gusty winds will be
possible from late Thursday into Friday. A warming trend is then
expected for the upcoming weekend as high pressure rebuilds over
.DISCUSSION...as of 01:56 PM PDT Wednesday...High pressure aloft
has resulted in mainly clear skies and seasonably mild
temperatures across the region this afternoon. Meanwhile,
unsettled conditions continue to impact the Pacific Northwest and
northern California as a system approaches from the north. This
system will dive southward overnight as the main mid/upper level
trough pushes inland well to our north. This system will bring a
slight chance of light precipitation to portions of the region
beginning late tonight over the North Bay and then through the San
Francisco Bay Area and Central coast early Thursday morning. Most
of the short-rage models show this system producing only very
light rainfall amounts, generally a few hundredths of an inch or
so for locations that do experience precipitation. However, this
may result in wet roadways for the Thursday morning commute across
much of the greater San Francisco Bay Area.
In wake of this frontal passage, daytime temperatures on Thursday
will be at least 5 to 10 degrees cooler compared to today.
Conditions will likely feel even cooler as breezy northerly winds
develop region-wide. Wind speeds are forecast to increase further
Thursday night into Friday as the main upper level system drops
southward into the Desert Southwest and surface pressure gradients
tighten along the coast. With this, the strongest winds are
likely in the higher elevations across the region with wind gusts
in excess of 45 MPH likely. Thus, a wind advisory will likely be
posted overnight in the hills/mountains for the Thursday
Night/Friday time frame.
While winds are forecast to diminish some late Friday into
Saturday, cannot rule out breezy conditions in some of the higher
elevations. However, a warming trend is expected for the weekend
as high pressure rebuilds back over the region as the mid/upper
level trough exits to the east. Temperatures fall back to near
seasonal averages for early next week as northwesterly flow aloft
returns and another weather system pushes inland to our north.
With that said, dry weather conditions are likely to persist for
our region through the middle of next week.
The longer range guidance continues to show a return to wet
weather conditions by late next week. The models generally agree
that a more potent weather system will drop southward into
northern California by Thursday or Friday of next week with a
moderate moisture tap. Both the GFS and ECMWF show widespread
rainfall across the region by next Friday. However, being more
than a week out, confidence remains low at this time and changes
to the forecast are likely.
.AVIATION...as of 10:30 am...Clear skies with light winds this
morning. Winds will increase in the afternoon as onshore gradients
tighten up. Models consistent in bringing low level moisture into
the area after 06Z as a strong shortwave approaches the area.
This will translate into IFR cigs over most terminals. Clearing
will take rapidly Thursday morning after the shortwave passes.
Vicinity of KSFO...VFR today with west winds to gusting to 25 kt
after 20Z. IFR cigs after 06Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR today. IFR after 06Z.
.MARINE...as of 08:57 AM PDT Wednesday...High pressure off the
California coast will keep moderate northwest winds through the
day. Winds will briefly decrease tonight as the high weakens but
will increase again Thursday through Friday as strong low
pressure develops over the Intermountain region.
.Tngt...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 from 3 AM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 AM
SCA...Rough Bar Advisory for SF Bar until 6 PM
SCA...Mry Bay until 3 AM
SCA...SF Bay until 9 PM
PUBLIC FORECAST: RGass
AVIATION: W Pi
MARINE: W Pi
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, twitter, and youtube at: