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

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000
FXUS66 KMTR 300049
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
549 PM PDT MON AUG 29 2016

.SYNOPSIS...An upper level system and associated cold front will
push through the region overnight tonight into early Tuesday morning
and result in breezy winds, slightly cooler temperatures and the
slight possibility of dry thunderstorms over the North Bay. A broad
troughing pattern over the West Coast will result dry weather
conditions along with temperatures below seasonal averages through
the remainder of the week.

&&

.DISCUSSION...as of 02:18 PM PDT Monday...While the marine layer
remains between 1500 and 1800 feet in depth this afternoon, low
clouds mixed out across the region and gave way to mostly sunny
conditions region-wide. However, mid/high level clouds continue to
move overhead in advance of an approaching mid/upper level
disturbance and associated frontal boundary. This system is
forecast to sweep through the region overnight into early Tuesday
morning and bring a slight chance of elevated/high based
convection over the North Bay. While the threat for dry
thunderstorms remains low, cannot rule out the possibility with
increased instability and modest mid/upper level moisture
advection interacting with the short-wave disturbance forecast to
push inland over northern California. The latest forecast models
have trended northward with the greatest threat, but worth keeping
in the forecast at this time. In addition, northwest winds will
increase ahead of and just behind the frontal passage with wind
gusts in the 30 to 40 MPH range along the coastal ranges,
especially over the Central Coast from late tonight into Tuesday
morning.

In wake of the frontal passage, the airmass will become more stable
by Tuesday afternoon with the threat for convection diminishing and
wind speeds relaxing late in the day. Temperatures will generally be
a few to several degrees cooler compared this afternoon as well. Do
expect some disruptions to the depth of the marine layer, however
should see enough boundary layer moisture to allow for low clouds to
return to the coast tonight and spread locally inland through
Tuesday morning.

A longwave trough is then forecast to remain stretched along much of
the West Coast through late week. This will keep temperatures below
seasonal averages, especially inland, with rounds of
overnight/morning low clouds that will give way to mostly sunny
conditions each afternoon. In addition, should see continued dry
weather conditions outside of the potential for coastal drizzle late
in the week.

&&

.AVIATION...as of 5:49 PM PDT Monday...Drier air and increasing
vertical mixing near the marine inversion rapidly eroded the
stratus and fog since late morning, textbook example for our area
of a warm-cool seasonal transition taking place in the nearest
term. In general, looks like decent chances for VFR to hold area-
wide this evening as mixing becomes increasingly focused and
continues based on recent model output`s handling of a deep
layered trough and cold air advection pattern banking up against
the sub-tropical ridge presently over CA. Today`s NAM run nearly
in-line with present SFO-SMX 3 mb gradient, which is forecast to
hold this strong if not become a little stronger between 4 and 5
mb tonight into Tuesday. Bottom line, areas gusty winds on coast
with decent chances VFR persisting this evening, then low to very
low confidence in stratus and fog redevelopment late tonight and
Tuesday morning.

Vicinity of KSFO...Westerly winds with gusts to the 20 knot range
this evening, fairly high confidence VFR persists this evening.
Westerly winds may subside later this evening and overnight, but
potential is there for it to be a slow process. As long as mixing
prevails and high cloud cover with sub-tropical jet persist, surface
winds will probably stay a bit gusty. Low confidence tempo MVFR
cig 12z-16z Tuesday. Pretty decent chances VFR returns during the
day Tuesday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Similar to the Bay Area, VFR stands a
pretty good chance of persisting this evening. Low confidence MVFR
cigs 05z-09z followed by MVFR cigs into Tuesday morning. VFR returning
late Tuesday morning, clearing could be quick process and thus possibly
earlier than usual.

&&

.MARINE...as of 02:18 PM PDT Monday...High pressure off the coast
of central California will cause a tightening of the pressure
gradient over the coastal waters this afternoon through midweek.
As a result, northerly winds and steep short period waves will
build on top of a small southerly swell. Expect near gale to gale
conditions in the lee of prominent point such as Point Sur.
Conditions are forecast to remain strong into the weekend, though
an approaching upper trough may disrupt this pattern.

&&

.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 Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Mry Bay until 9 PM
             SCA...SF Bay until 3 AM

&&

$$

PUBLIC FORECAST: RGass
AVIATION: Canepa
MARINE: BFG


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