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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMTR 200013
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
513 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 4:50 PM PDT Tuesday...For 00z Tafs. Mainly clear
skies prevail in the post-frontal/mixed boundary layer environment
this afternoon. High clouds are anticipated to increase tonight as
an upper level trough dig south over Northern
California. Confidence is low that a few MVFR/IFR scattered to
broken cig may possible develop early Wednesday morning. Have kept
a TEMPO group from 12z-17z. Moderate to locally gusty winds will
continue through this evening then ease overnight. Winds are
anticipated to increase once again Wednesday afternoon as the
trough swings through.

Low confidence with regard to cigs returning.

Vicinity of KSFO...VFR conditions will prevail through tonight.
Broken MVFR cig possible between 13z-17z early Wednesday morning.
Low confidence. Sustained west winds of 15 to 20 kt with gusts
around 25 to 30 kt through this evening. Winds will ease to around
10 to 15 kt overnight.

SFO Bridge Approach...similar to KSFO.

Monterey Bay Terminals...VFR conditions will prevail through tonight.
Broken IFR cig possible between 12z-16z early Wednesday morning.
Low confidence. Sustained west winds of 10 to 15 kt with gusts
to 20 kt through this evening. Winds will ease becoming light
overnight.

&&

.MARINE...as of 04:40 PM PDT Tuesday...The first long period
northwest swell of the season is arriving today and will persist
through midweek. Increasing high pressure off the coast will bring
moderate, locally gusty, northwest winds through tonight.
Decreasing winds during the day Wednesday will  increase again by
Wednesday night.

&&

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

&&

$$

PUBLIC FORECAST: Rowe
AVIATION: CW
MARINE: DRP

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.