Technical NOAA Weather Discussion

FXUS66 KMTR 152059
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
159 PM PDT Sat Jun 15 2019

.SYNOPSIS...A well defined marine layer will keep temperatures on
the cool side of normal today. On Sunday a few degrees of warming
away from the coast as high pressure begins to build. A more
noted inland warming trend develops early next week as high
pressure strengthens while onshore flow will persist along the
coast.

&&

.DISCUSSION...as of 02:00 PM PDT Saturday...Visible satellite
imagery shows marine stratus across the entirety of the coastal
waters as well as the immediate coastline from Sonoma county
through Big Sur (but excluding the sheltered Santa Cruz county).
Meanwhile, the Fort Ord Profiler indicates the marine layer depth
has held fairly steady at around 2200 feet throughout the course
of the day though actual cloud bases have steadily risen since
sunrise. Afternoon temperatures are running a few to several
degrees cooler than this same time yesterday and so far today is
on track to be the coolest day of the last week as well as the
coolest day of the next several days.

For tonight, expect a robust marine layer to once again inundate
the low lying elevations, to a depth of around 1800-2000 feet.
Patchy fog and coastal drizzle should also once again return given
the slow compression of the marine layer from aloft.

A 596dm 500mb high pressure will build into the region from
Sunday through early next week, heralding in a tangibly warmer,
drier airmass across the broader region. That said, near to long
range models are all in agreement that robust onshore maritime
air mass regime with onshore winds will remain in place and keep
locations near and in some proximity to the coast relatively
cooler than the surrounding inland areas.

Furthermore, the last 3-4 runs of the ensemble models have
progressively come in a degree or two cooler than each of the
previous runs for the early next week period, with the warmest
runs coming in 2-3 days ago. Likewise, the error and magnitude of
the outliers has decreased in these ensemble model runs,
indicating increasing confidence that temperatures will not be
quite as hot through early next week as models previously
advertised. As such, have updated the temperature forecast and
nudged it downward, particularly for the inland locations
throughout early next week.

Moving forward, the key things to watch with the new model data
today will be a) any change in the location/strength of the
building offshore ridge which could alter the direction and
magnitude of our winds during the warmest days early next week and
b) the impacts of a weak upper disturbance rotating over and
around the ridge through the coming days.

By midweek next week, a digging upper low will displace the
influence of the ridge over California and gradually introduce a
cooling trend regionwide from Wednesday through the coming
weekend.

&&

.AVIATION...as of 10:44 AM PDT Saturday...A deep marine layer
will mean later clearing at the terminals today. Onshore sea
breeze winds will increase this afternoon. A well defined marine
layer and onshore winds tonight will usher stratus and patchy fog
back inland tonight and Sunday morning.

Vicinity of KSFO...MVFR cig through at least 20Z, west wind increasing
to 15-20 knots in the afternoon. MVFR cig redeveloping tonight.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR cigs, some clearing this afternoon.
Stratus returning in the evening with MVFR-IFR cigs developing.

&&

.MARINE...as of 8:28 AM PDT Saturday...High pressure off the
northern California coast will allow moderate northwest winds to
prevail over the northern waters through Monday. Locally breezy
conditions can also be expected along the Big Sur coast through
Saturday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 6 PM
             SCA...SF Bay until 9 PM

&&

$$

PUBLIC FORECAST: DRP
AVIATION: Sims
MARINE: Sims

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



  
Prepared by Boulder-Creek.com Weather at: Sat Jun 15 16:30:02 PDT 2019
From the National Weather Service