National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMTR 151829
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1029 AM PST Fri Nov 15 2019

.SYNOPSIS...A weak front will move through the North Bay this
morning with some light showers or sprinkles possible. Elsewhere
skies will be cloudy this morning then turning partly sunny by
this afternoon. High pressure builds Saturday through Monday with
a warming and drying trend as light offshore winds develop in the
hills. Cooling by Tuesday as the ridge breaks down as the next
front drops through the Bay Area by Wednesday but the best rain
chances stay over the Sierra and eventually Southern California.

&&

.DISCUSSION...as of 9:00 AM PST Friday...A weak frontal system
continues to push through the North Bay this early morning,
bringing with it some very light and isolated rain showers. A few
stations across the North Bay have recorded a hundredth of an inch
or two of rain over the past 3 hours, including 0.01" at the
Hawkeye RAWS in northern Sonoma County. Going back over the past
24 hours, rainfall amounts region-wide ranged from little/no rain
up to about a tenth of an inch. Downtown San Francisco has
received 0.02" over the past 24 hours, bringing the water year
total up to 0.03". As the day progresses, sky cover will gradually
decrease with afternoon highs warming to about 2 to 6 degrees
above middle November climatology. Forecast package remains on
track with no planned updates to the short-term. For additional
details, please refer to the previous discussion section.

&&

.PREV DISCUSSION...as of 3:29 AM PST Friday...For the first time
in a while we`ve put the radar into precip mode. A weak front is
currently draped across Mendocino county and shifting towards
Sonoma County. Elevated returns are showing up over the coastal
waters west of Bodega Bay with some light showers or sprinkles
possible this morning, mainly across Sonoma county. So far not
seeing any tips of the bucket but there is plenty of low level
moisture and enough synoptic lift to generate some drizzle/light
showers/sprinkles through about 18z this morning. Other locations
will start out cloudy, with some dense pockets of fog. There will
be a trend towards partly sunny skies by midday or early afternoon
as high pressure quickly builds over the region.

The surface pattern then supports some light offshore winds
developing in the hills overnight. The ridge will be building in
so quick and offshore winds light enough that residual clouds will
likely persist near the coast and coastal valleys into Saturday
morning.

Noted warming trend develops Saturday through the weekend with
afternoon highs back into the 70s, warmest readings on Sunday as
the ridge peaks. So the stage is set for an ideal Bay Area weekend
with plenty of sunshine and comfy afternoon temps in the 70s.
Overnight lows wont be as cold as recently as the airmass is more
moist with higher dewpoints allowing for milder nights in the 40s
most locations.

Monday still looking like a nice day but the ridge weakens
slightly and offshore flow eases by afternoon as the next Pacific
trough approaches the region.

Much cooler by Tuesday as a mainly dry upper trough and surface
cold front will move through the Bay Area. The best chance for
precip will be over the Sierra though cant completely rule out
some local showers. Though nothing of significance is forecast at
this time.

The boundary will drop into SoCal and then tap into some deeper
moisture such that the Sierra and SoCal could eventually get some
moderate precip while the Bay Area remains mostly dry.

The long range trends then suggest dry and seasonable later next
week and into next weekend. Looking out towards Thanksgiving the
PNA ensembles show more members trending negative (cooler and
wetter pattern for NorCal). This then gives some credence to some
of the long range ensembles (eps/gefs) showing precip by the last
week of the month.

&&

.AVIATION...as of 10:00 AM PST Friday...for 18z TAFs. Broken low
clouds are slowly scattering out at this hour. Mainly clear skies
expected inland today with lingering scattered clouds expected
along the coast. A weak front will dissipate as it moves through
today. As high pressure begins to build overhead this evening, low
level moisture will result in some cigs overnight. Confidence is
low. Generally light winds will persist this morning with west
winds developing this afternoon.

Vicinity of KSFO...MVFR cigs around 2700-2800 feet will linger
through this morning then briefly scatter out early this
afternoon. A weak front will move across the region today. MVFR
cigs may return the evening with bases potentially lowering to
IFR overnight tonight. Light winds this morning becoming westerly
and breezy this afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR/VFR cigs will scatter our shortly
becoming VFR for the remainder of the morning. Light winds this
morning becoming onshore this afternoon. Will see a return to
MVFR cigs this evening with bases lowering to 1000-2000 feet
overnight.

&&

.MARINE...as of 8:56 AM PST Friday...Light rain along a cold
front will occur this morning across the northern waters. Winds
will shift to the northwest today behind a cold front and
gradually increase through tonight. A relatively large, long
period northwest swell will increase this morning and persist
through Saturday. Wave heights around 10 feet with breezy to gusty
northwest winds will create hazardous conditions for small crafts
today through Saturday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 PM
             SCA...Pt Arena to Pt Reyes 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...Pt Reyes to Pigeon Pt 0-10 nm from 3 PM

&&

$$

PUBLIC FORECAST: Rowe/RWW
AVIATION: CW
MARINE: ST/CW

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