Strong Wind in California, January 1, 2019

Area Forecast Discussion
National Weather Service San Francisco Bay Area
939 PM PST Mon Dec 31 2018

.SYNOPSIS...Dry conditions with seasonable highs and cold overnight
lows will prevail through the remainder of the work week. Gusty
north winds will continue to impact the higher elevations of the
San Francisco Bay Area through mid morning Tuesday. Temperatures
may fall below freezing in the colder valleys late Monday night
into early Tuesday, but more widespread freezing temperatures are
possible late Tuesday night into early Wednesday. A chance of
rain finally returns to the forecast next weekend.

&&

.DISCUSSION...As of 8:45 PM PST Monday...It's a blustery and cold
New Year's Eve across our region. In the hills, winds subsided a
bit late this afternoon, but are now beginning to increase once
again as surface high pressure builds over northern Nevada. Winds
from the north and northeast are gusting between 40 and 50 mph in
the North and East Bay Hills, with local gusts of between 60 and
70 mph atop Mount Saint Helena and Mount Diablo. Based on the
latest local WRF, these gusty winds will persist in the hills
overnight and into early New Year's morning, and may even increase
further on the highest peaks. Will continue with a Wind Advisory
for elevations above 1000 feet in the North and East Bay Hills
through 10 am Tuesday. Winds are not as strong in the Santa Cruz
Mountains and winds there are not expected to increase much
overnight. Thus, will likely cancel the Wind Advisory for the
Santa Cruz Mountains shortly.

Near sea level, winds continue to gust to around 30 mph around San
Francisco Bay and locally in the North and East Bay Valleys.
Winds are not currently meeting wind advisory criteria near sea
level and wind speeds are expected to trend lower through the
night. Therefore, the Wind Advisory for the San Francisco
Bayside areas and East Bay Valleys will be allowed to expire at 9
pm. Although the lower elevation wind advisory will expire at 9
pm, brisk winds will continue through at least midnight, lowering
wind chills into the upper 20s and 30s across our region by the
time the New Year arrives. Anyone venturing out to celebrate the
New Year is urged to bundle up and take these cold conditions
seriously.

The cold and very dry airmass that swept into our region today
will result in cold nighttime temperatures for much of the
remainder of the work week. Breezy conditions tonight in the San
Francisco Bay Area will maintain mixing and help hold temperatures
up a bit. Thus, it's likely that model guidance for much of the
Bay Area is too cold tonight and expect only isolated wind-
sheltered valleys to drop to around freezing by sunrise Tuesday.
Farther south, where winds will be lighter overnight, freezing
temperatures are likely in the colder valleys, especially the
valleys of southern Monterey County. A freeze warning will soon
be issued for the southern Salinas Valley and adjoining inland
valleys for late tonight through mid morning Tuesday.

More widespread freezing temperatures are likely late Tuesday
night into Wednesday morning as the cold/dry airmass persists and
as winds subside in all areas. Will almost certainly need another
freeze warning for our southern inland valleys, but may also need
to consider freeze warnings for the North Bay Valleys and
southern Santa Clara Valley. In addition, some of the colder
coastal locations, such as areas around Monterey Bay, may dip down
to around freezing late Tuesday night and early Wednesday, and we
may need frost advisories for those locations. Nighttime
temperatures are forecast to gradually moderate Wednesday night
and Thursday night as a shortwave ridge builds over California.
However, cold air will remain trapped in the inland valleys and so
cold nights will persist in those areas for most of the work
week.

The models have been consistent in developing a significant
pattern change late in the week and into the upcoming weekend as
the upper ridge off the West Coast finally breaks down and allows
Pacific storms to bring rain to California. The details are tough
to pin down at this time due to model differences on timing and
rainfall intensity. However, forecast confidence is increasing
that this pattern change will develop and our area will see wet
weather beginning as early as Friday night, but almost certainly
over the weekend and into early next week.

&&

.AVIATION....As of 9:45 PM PST Monday...Winds continue to gust to
around 25-30 kt over the SFO Bay Area. These winds are forecast to
abate early Tuesday morning. Clear VFR through the period. Models
indicate the strongest winds occurring today then decreasing
slightly tonight. Could see LLWS near the North and East Bay Hills
impacting STS and OAK through 15Z Tuesday morning.

Vicinity of KSFO...VFR. Northerly winds gusting to 25 kt becoming
northeast and decreasing after 14Z.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Southeast drainage winds in the
Salinas Valley to impact SNS with winds to 15 kt after 07Z.

&&

.MARINE...as of 09:35 PM PST Monday...A 1010 mb low is centered
just SW of San Diego while a 1031 mb high is 600 miles west of
Cape Mendocino. Gusty north to northeast winds will decrease over
the coastal waters tonight and over the bays Tuesday as the low
weakens. A long period northwest swell  will arrive on Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...Wind Advisory...CAZ006-507-508-510-511
             Freeze Warning...CAZ516
             SCA...SF Bay
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM

&&

PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi

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