National Weather Service Raw Text Product

Displaying AFOS PIL: AFDMTR Received: 2018-01-12 16:28 UTC


709 
FXUS66 KMTR 121628
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
828 AM PST Fri Jan 12 2018

.SYNOPSIS...High pressure will build over California today and 
bring dry and mild weather to the area through the Martin Luther 
King Jr. Holiday Weekend. The next chance of rain will be on 
Monday night and Tuesday, with additional rain chances next 
Thursday and Friday.

&&

.DISCUSSION...As of 8:20 AM PST Friday...Patchy fog continues
around our region this morning with many spots under two miles.
Worst conditions appear to be over the East Bay Interior valleys
with less than 1/2 mile in many spots. Upper air sounding nicely
showed the surface inversion which gave favorable conditions today
for fog development. Conditions will improve later this morning
with upper 50s to the mid 60s forecast. 

Latest models in are fairly close to the previous couple of runs.
Look for rainfall to return on Tuesday with a second round slated
for Thursday.

.PREVIOUS DISCUSSION....Satellite fog product is showing low 
clouds over a portion of the coastal waters, and also spreading 
through most inland valleys at this time. There is also a fair 
amount of fog being reported at area airports with visibilities 
bouncing around from 1/4 mile to 7 miles at our TAF sites. A dense
fog advisory may be needed towards dawn if 1/4 mile or less 
becomes more widespread. Otherwise, today should see warmer high 
temperatures with most locations seeing highs in the 60s. Even 
warmer temperatures are anticipated for Saturday and Sunday as 
high pressure aloft builds over the state, and warmest inland 
areas could see highs in the mid 70s.

The next rain event is forecast to begin late Monday as an upper
level trough approaches the coast. Light rain is expected to begin
across much of the San Francisco Bay Area by late Monday night 
and early Tuesday, and then reaching the Monterey Bay area Tuesday
morning. The heaviest rainfall is expected to be mostly north of 
our CWA but northern Sonoma and Napa counties could see periods of
moderate rainfall at times. This system is expected to be through
our area by midday Tuesday with perhaps some lingering early 
afternoon showers. Rainfall totals with the Monday Night/Tuesday 
system are currently forecast to range from 0.25-0.75" in the 
North Bay...locally up to 1.25" in the far northern coastal 
mountains...and generally a third of an inch of less south of the 
Golden Gate.

A second system is forecast to impact the district with 
widespread rain on Thursday with showers continuing into Friday. 
This second system is currently expected to be about as wet as the
first (or somewhat wetter for areas from San Francisco 
southward). Medium range models still indicate another system 
after next weekend. 

&&

.AVIATION...as of 3:51 AM PST Friday...For 12z tafs. Big concern
for high impact fog event today at Bay Area terminals. Nearly all
sites have been bouncing around from 1/4 mile to 6 plus at times
overnight. Goes-16 fog product shows much of the Bay filled in at
this hour. With light winds, moist boundary layer and inversion 
aloft the fog/low clouds will be slow to mix out. Optimistic taf 
will show late morning but that can easily turn to early 
afternoon this time of year with low sun angle.
 
Vicinity of KSFO...Concern for dense fog at times from now through
at least 16z and possibly beyond. Web cams show fog and there have
been varying reports around the region all night. Satellite fog
product looks ominous. Usually conditions get worse as the sun 
comes up. Potential that clearing may not occur until early 
afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Dense fog in the Salinas Valley could
briefly impact kmry as it burns off but main impact will be ksns
this morning, otherwise mostly clear.

&&

.MARINE...as of 03:44 AM PST Friday...Generally light winds over
the waters today except south of Point Pinos where stronger north
winds will persist. Long period swells will continue to pass
through the waters heading into the weekend with seas building
rapidly by Monday. Several storms and associated cold fronts will
pass through the waters next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm

&&

$$

PUBLIC FORECAST: Bell/Sims
AVIATION: RWW
MARINE: RWW

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