Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 221153
Area Forecast Discussion
National Weather Service San Francisco Bay Area
353 AM PST Wed Feb 22 2017
.SYNOPSIS...A few lingering showers will be possible today into
early Thursday morning, mainly offshore and near the coast.
Otherwise, drier and much cooler conditions are forecast through
late week with chilly overnight/morning temperatures. Unsettled
weather conditions return by the weekend with the potential for
widespread rain and gusty winds.
.DISCUSSION...as of 02:46 AM PST Wednesday...KMUX Radar this
morning showing only a few lingering showers moving across the
region, generally over Monterey County and adjacent coastal waters
inland across portions of San Benito County. Expecting this trend
to continue through the next few hours with mostly dry conditions
developing region-wide later in the morning. As a colder, drier
air mass settled into the region, temperatures this morning are
running about 5 to as much as 15 degrees cooler compared to 24
hours ago under mostly clear skies. This too will lead to cooler
daytime temperatures today with low to mid 50s likely in the lower
elevations and 40s more common in the hills. While much of the day
will be dry, especially for inland areas, cannot rule out an
isolated shower or two late tonight into early Thursday morning as
a weak weather system drops southward down the coast. The best
chance for showers will likely be over the coastal waters and
along the coastal ranges while inland areas will likely remain dry
through much of the day Friday.
The aforementioned cooler air mass settling into the region
combined with light winds will allow for some of the coolest
overnight/morning temperatures the region has seen in a while. As
850MB temperatures cool down to between 0 and -4 C mid/late week,
surface temperatures will likely fall into the 30s region wide,
even upper 30s to near 40 near the coast. Inland, wind sheltered
areas can expect a period of sub freezing temperatures both late
tonight/Thursday morning and again Thursday night/Friday morning.
With this too, patchy frost will be possible in the coldest,
inland valley locations. In addition, with this colder air mass in
place, cannot rule out a few snow showers in the highest
elevations of the Santa Cruz and Santa Lucia mountains overnight
into early Thursday morning.
By the upcoming weekend, the forecast models continue to show the
potential for a cool, wet weather pattern returning to the region.
While the ECMWF solution has backed off on precipitation from late
this week into the upcoming weekend, the GFS and Canadian models
remain wet from late Saturday into Sunday with lingering showers
into early next week. The models generally agree with a cold,
mid/upper level system dropping southward out of the Gulf of
Alaska and intersecting a more moist system approaching from the
west. The GFS and Canadian solutions bring widespread rainfall and
strong gusty winds to the region this weekend as the systems merge
well offshore and approach the central California coast. This set
up would also likely bring a deep surface low toward the coast and
result in the potential for strong winds. The past 2 model runs of
the ECMWF no longer shows the system from the north merging with
deeper moisture and thus, brings less precipitation to the region.
Regardless, somewhat unsettled conditions appear likely late in
the forecast period with chances of some precipitation. As we are
still 3 to 5 days out, do expect to see the models come into
better focus in the coming days. Folks are urged to stay up-to-
date with the latest forecast as we fine tune details for the
.AVIATION...As of 3:38 AM PST Wednesday...For 12z Tafs. Current IR satellite
shows a few low clouds across the district, with fog being
reported at KSTS. Most terminals are reporting VFR conditions at
this hour. VFR should prevail through the day, but cannot rule out
a couple of hours of MVFR CIGs at times due to existing low level
moisture that is still present. Not enough confidence to mention
in tafs. The main concern today will be the winds across the
region. West/northwest winds will increase later this morning and
become gusty by early afternoon. Sustained onshore winds will
range between 10 and 20 kt through afternoon and evening, with
gusts 20-25 kt, locally higher. Winds are forecast to subside late
tonight. Fog likely returns in and around KSTS tonight. Low
confidence on CIGs. Moderate to high confidence on winds.
Vicinity of KSFO...Mainly VFR. Breezy onshore winds, gusty by
afternoon hours, ranging 10-20 kt with gusts up to 25 kt. Winds
decrease late tonight or early Thursday morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Mainly VFR today. Moderate and gusty
onshore winds by early afternoon.
.MARINE...as of 02:46 AM PST Wednesday...Building high pressure
over the eastern Pacific with bring increasing northwest winds to
the southern waters starting late this morning...then extending
northward to the remainder of the waters through the afternoon and
evening. Northwest swell will be on a decreasing trend through
the rest of the week. Winds turn southerly by Saturday as another
storm system approaches. South winds become strong over the
weekend...generating fresh swell that will make seas very rough.
.Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 2 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 2 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 AM
SCA...Rough Bar Advisory for SF Bar
SCA...Mry Bay from 2 PM
PUBLIC FORECAST: RGass
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