Rip Current in California, February 21, 2021

Area Forecast Discussion
National Weather Service San Francisco Bay Area
130 PM PST Sun Feb 21 2021

.SYNOPSIS...A warming trend through the first half of the week
will be followed by a slight cooling trend from Wednesday through
the weekend. Expect periods of gusty offshore winds throughout the
week, mainly across higher elevations. Dry conditions will also
dominate through the end of the month.

&&

.DISCUSSION...as of 01:30 PM PST Sunday...Temperatures are
finally warming up this afternoon with most areas currently in the
low 60s as high pressure remains off the northern California
coast. Expect some additional warming this afternoon with highs
mostly in the 60s and sunny skies. Breezy winds also continue to
subside compared to this morning when the North and East Bay Hills
were seeing local gusts of 50-60 mph. After diminishing this
afternoon, models show breezy offshore winds returning to the
North Bay Mountains overnight tonight before weakening tomorrow
morning. The warming trend will continue tomorrow and Tuesday as
high pressure builds offshore and stretches eastward into
California. Widespread upper 60s to low 70s across the region
tomorrow or about 5 to 10 degrees above seasonal normals. Some
slight additional warming is expected on Tuesday before gradually
cooling the rest of the week.

The first in a series of shortwave troughs will move inland north
of Nevada into Tuesday. As this occurs, offshore winds will
increase across the hills of the North Bay Monday night before
spreading southward to the East Bay Hills and Santa Cruz Mountains
Tuesday morning. For this wave, gusty winds are expected mainly to
be confined to the higher terrain areas where gusts of 40-50 mph
will be possible (locally higher at tallest peaks). Another
shortwave trough will move into the interior on Wednesday, this
time a bit further westward, before dropping into the Desert
Southwest into Thursday. Therefore, offshore winds will likely
remain gusty in the hills Tuesday evening before increasing in
intensity and becoming more widespread Wednesday morning. This
second system will bring stronger winds aloft than the first with
greater potential for gust to mix down to lower elevations as well
(~25-35 mph with occasional gusts to 40 mph possible). This may
cause difficulties with temporary outdoor structures. The latest
NAM as well as the local WRF show 925 mb winds over Napa County in
excess of 50 kt early Wednesday morning. The North and East Bay
Hills may see gusts of 50-65+ mph on Wednesday and Wednesday night
with the strongest winds over the mountains of Napa County. Will
monitor closely and evaluate the need for any advisory products in
the next day or so.

Yet another trough will then drop southward into the interior from
the Pacific Northwest into Saturday bringing more gusty offshore
winds to the region Saturday to Sunday morning. Stronger gusts may
also mix down the surface with this system as many ensemble
members from the ECMWF are already showing gusts of 35-40+ mph at
KSFO. This is still fairly far out in time and is not yet covered
by the higher resolution models. Will have more details over the
coming days.

Dry conditions are still forecast to dominate through the end of
February. Both the GFS and ECMWF hint at possible precipitation in
the first few days of March as the upper high retreats westward
towards the north central Pacific. The ECMWF is still a little
wetter both in the deterministic and ensemble runs than the GFS.
Weeklies also still showing a shift towards a more zonal pattern
early next month which would give the area a better shot at
receiving more moisture. Will continue to keep a close eye out
for any potential precipitation.

&&

.AVIATION...as of 09:45 AM PST Sunday...For the 18Z TAFs. VFR
prevailing through the taf period with clear skies and light
winds. Only a few high clouds observed on satellite. Some light
onshore breezes this afternoon near the coast. Possible llws
overnight into early Monday morning, as northerly winds increase
to near 30 kt at 2000 ft AGL. Most likely impacts are to North Bay
terminals.

Vicinity of KSFO...VFR with light to calm wind. Light sea breeze
developing this afternoon. VFR through the period with mostly
clear skies.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. Light to calm winds. Light sea
breeze developing this afternoon with clear skies. Continued VFR
overnight with light ESE winds.

&&

.MARINE...as of 08:46 AM PST Sunday...Expect gusty north to
northwest winds early this week as strong high pressure sits over
the eastern Pacific and northern California. A moderate period
northwest swell will continue this week. Strong and steep wind
waves, along with moderately strong swell will continue to create
hazardous seas conditions for smaller vessels through early in the
upcoming week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm until 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM

&&

PUBLIC FORECAST: AS
AVIATION: Lorber
MARINE: Gass

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