Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 191908
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1208 PM PDT Tue Sep 19 2017

.SYNOPSIS...An upper level low will dominate the western US
through this week. There is a slight chance of rain in the far
North Bay Wednesday morning as a frontal system moves through
otherwise look for dry and breezy conditions with cooler than
average temperatures. A slow warming trend is expected by the
weekend.

&&

.DISCUSSION...as of 12:08 PM PDT Tuesday...Pleasant and breezy
conditions will prevail this afternoon for the San Francisco Bay
Area and central California coast. Aside from a few passing high
clouds, most areas can expect plentiful sunshine through the
afternoon with highs ranging in the 60s along the coast and 70s to
low 80s for interior locations. These high temperatures equate to
about 5 to 10 degrees below middle/late September climatological
normals. An upper level low pressure system centered near 53N,
138W, or about 750 miles NW of Seattle, is largely responsible for
maintaining below normal temperatures in our area, as well as
helping to produce moderate precipitation for parts of Oregon and
Washington State over the next few days.

As this upper level low continues to approach the Pacific
Northwest over the next few days, we`ll see a series of
shortwaves ripple through the longwave trough and bring the
potential for some light precipitation for parts of the North Bay.
Models have been in fair agreement with painting some very light
QPF over northern Sonoma County beginning late tonight and
continuing into Wednesday morning. Wouldn`t be surprised if
communities such as Cloverdale or even Healdsburg see sprinkles
and/or wet roadways for the Wednesday morning commute.

While most of the San Francisco Bay Area and central California
coast won`t see any precipitation, winds are forecast to increase
over much of the area with some of the ridges and higher
elevations likely to see wind gusts in excess of 30 or 35 mph.
Even some of the wind-prone low-lying areas such as San Francisco
International Airport can expect breezy and gusty winds off/on
over the next several days, with the breeziest conditions most
likely in the afternoon and evening hours around sunset.

Additionally, the first good long-period northwest swell of the
season will move through the coastal waters over the next few
days. This will bring coastal hazards to the northwest-facing
beaches with an increased likelihood of rip currents, large shore
breaks, and sneaker waves. As a result, a Beach Hazards Statement
will remain into effect through Thursday evening. If your plans
take you to the beach this week, please exercise beach safety and
never turn your back to the ocean.

By the end of the work week, the longwave trough will push inland
to the North American continent as a ridge builds back behind it
in the eastern Pacific. This ridge will help to boost afternoon
highs back to near normal, and possibly above normal by Sunday and
into the first part of next week.

&&

.AVIATION...As of 11:10 AM PDT Tuesday...For 18z Tafs. Well mixed
marine layer in postfrontal environment bringing widespread VFR
this morning. Onshore winds will be breezy with sustained winds up
to 22kts possible by the afternoon, with gusts up to 30 kt
possible in the windiest areas. For tonight, upper trough digs
closer to the region, bringing some high clouds, but primarily
keeps marine layer mixed. Some intermittent MVFR/IFR SCT-BKN
posbl in the pre- dawn to late morning on WED, represented by
TEMPO btwn 11-17Z depending on location. Otherwise, VFR with
continued onshore regime anticipated for tomorrow.

Vicinity of KSFO...VFR. Sust onshore winds 15-20kt through the
remainder of the day, with gusts 25 to 30kt. Dirty feed tomorrow
expected to bring intermittent MVFR SCT-BKN below 1600 feet btwn
12-17Z WED.  Otherwise, VFR.

SFO Bridge Approach...similar to KSFO.

Monterey Bay Terminals...VFR. Sust onshore winds 10-15 kt, with
gusts to 20kt, locally higher along the immediate coast. Dirty
feed may bring patchy IFR/MVFR cigs from around sunrise to late
morning WED.

&&

.MARINE...as of 11:59 AM PDT Tuesday...Increasing high pressure
offshore will bring moderate, occasionally gusty northwest winds
through the coming days.  A  moderate sized, longer period
northwest swell will move through the waters beginning today.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .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
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Mry Bay
             SCA...SF Bay until 3 AM

&&

$$

PUBLIC FORECAST: Rowe
AVIATION: DRP
MARINE: DRP

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