Small Craft Advisory 31, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1042 PM PST Thu Mar 1 2018

.SYNOPSIS...A low pressure system over the Pacific Northwest will
continue to usher in colder, unstable air tonight into this weekend.
Showers, lowering snow levels, and a few thunderstorms are possible
during this time. Showers will gradually diminish by Saturday. A
drying trend is expected later Sunday through early next week. Another
low pressure system will possibly bring wet weather back mid to late
next week.

&&

.DISCUSSION...as of 9:50 PM PST Thursday...A soaking rain to start
off the first day of March has transitioned to showers this evening.
Strong southwest winds along the coastal terrain in the earlier
eastward advancing warm sector enhanced rain amounts up to and in
a few areas greater than previous GFS and ECMWF qpf forecasts had
while falling a bit more in-line with the higher resolution meso-
scale model output. North Bay totals were locally upwards of 2.5
inches to 3 inches, Kentfield reported 3.22 inches. A few spots in
the Santa Cruz Mountains had over 3 inches of rain. Along the Big
Sur Coast, Los Padres NF, Santa Lucia Mountains isolated amounts
have steadily climbed to 5 inches to 8.50 inches.

Strong and gusty winds to 50 mph are still reported over the North Bay
Mountains, but are expected to diminish this evening. The wind advisory
will be allowed to expire at 10 pm.

Low pressure over the Pacific Northwest will bring in colder, unstable
air into the forecast area tonight through Friday. Showers and a few
thunderstorms are possible during this time. Drier weather returns by
late Saturday and Sunday as a low amplitude mid level ridge develops.
The 00z GFS is in and forecasts the next chance of rain by the middle
of next week, within a 24 hour period of what today's 12z ECMWF was
forecasting. Overall looks like a decent chance we lean back toward
wet weather again mid to late next week with a relatively high northern
hemispheric wave number ideal for wave growth with a long wave trough
over the eastern Pacific. Details of return storminess, rain will of
course need to be looked at as the models hopefully become more in
agreement on next week's timing.

&&

.AVIATION...as of 10:30 PM PST Thursday...Upper low off the
Pacific Northwest coast will keep unsettled weather through
Saturday. Currently a line of showers is moving through the area.
Models show this line moving out of the area after 12Z. There
could be occasional MVFR cigs but VFR conditions expected after
12Z as cigs rise above 4000 ft. A break in the action is expected
until Friday afternoon when surface heating combined with the
cooling in the upper levels allows convective showers to develop.
Isolated thunderstorms are possible as will be small hail. West
to southwest winds gusting to 25 kt decreasing after 11Z.

Vicinity of KSFO...Occasional MVFR cigs through 11Z as rain
showers move through the area. Becoming VFR after 11Z. Southwest
to west winds gusting to 25 kt decreasing after 11Z. Possiblility
of thunderstorms or small hail Friday afternoon and early
evening.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR with cigs remaining above 3000 feet.
Southerly winds becoming westerly Friday afternoon.

&&

.MARINE...as of 10:24 PM PST Thursday...A 990 mb low off the
Washington coast will weaken as it moves toward the Oregon coast.
This will keep showers along with a slight chance for
thunderstorms through Friday night. Winds will  decrease overnight
becoming light over the weekend. Northwest  swell will increase
generating hazardous seas into the upcoming  weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Mry Bay
             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
             SCA...SF Bay until 3 AM

&&

PUBLIC FORECAST: Canepa
AVIATION: W Pi
MARINE: W Pi

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