NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 261022

Area Forecast Discussion
National Weather Service San Francisco Bay Area
322 AM PDT Sun Mar 26 2017

.SYNOPSIS...A weak weather system will spread light rain across
the North Bay this afternoon and across most of the remainder of
the forecast area this evening and overnight. Showers will mostly
end by Monday morning. Expect decreasing clouds on Monday with
brisk afternoon and evening northwest winds. High pressure will
then produce dry weather through midweek, along with a warming
trend. Shower chances will return to northern and eastern portions
of our region Wednesday night and Thursday as a weather system
drops inland to our east. Temporary cooling and blustery
conditions are also expected with this system.


.DISCUSSION...As of 3:20 AM PDT Sunday...High clouds have been
increasing overnight as a weak weather system approaches from the
west-northwest. The models have slowed the arrival of
precipitation with this system, with rain now expected to develop
only in the North Bay between midday and late afternoon. Most
areas south and east of San Francisco will probably remain dry
through late afternoon. Light rain is then expected to develop
over most of the remainder of our forecast area during the evening
hours. Rainfall totals through tonight are forecast to range from
0.10-0.40" in the North Bay, with totals mostly under a tenth of
an inch for all other areas.

A few showers may linger into Monday morning, but for the most
part Monday should be a dry day as the system departs quickly to
the southeast and a high pressure ridge builds just offshore.
Brisk northwest winds are likely by Monday afternoon with
strongest winds expected near the coast where local gusts up to 35
mph are possible late Monday afternoon and early evening.

The upper ridge offshore is forecast to build inland over
California on Tuesday and Wednesday, bringing dry weather along
with a warming trend. High temperatures by Wednesday are forecast
to be mostly in the upper 60s and 70s.

The GFS and ECMWF have come into better agreement regarding a
system that will impact our area shortly after midweek. Both
models show a system dropping in from the northwest and across far
northern California on Wednesday night, and then proceeding into
the Great Basin by Thursday. This system will be an `inside
slider` which will mean that most, if not all, precipitation will
be confined to areas to our north and east - which is what the
GFS is forecasting. However, the past two runs of the ECMWF have
forecast precipitation farther to the south and east and into our
area. Have therefore added shower chances across the northern and
eastern portions of our area for Wednesday Night and Thursday. A
cooler airmass will arrive with this system on Thursday and high
temperatures may cool by as much as 10 degrees from Wednesday to
Thursday. In addition, potentially quite strong and gusty north to
northwest winds will develop on Thursday and continue into
Thursday Night. Locally blustery conditions may then continue in
the hills into Friday night as well. If conditions develop as
currently forecast by the models, wind advisories may be needed
for portions of our forecast area later in the week.

Warming and drying will occur late in the week and into next
weekend as an upper ridge once again builds across California.


.AVIATION...As of 10:42 PM PDT Saturday...A few locations along
the immediate coastline are reporting MVFR cigs this evening
otherwise it`s VFR. Winds remain onshore through tonight the
pressure gradient then becoming near neutral SFO-SAC on Sunday.
Light rain with the next weather system reaches the North Bay
beginning late Sunday morning, light rain spreads southeast over
the remainder of the area through Sunday afternoon and evening.

Vicinity of KSFO...VFR. Tempo MVFR cig 11z-15z Sunday. Light rain is
predicted to begin early Sunday evening.

SFO Bridge Approach...Same as KSFO.

Monterey Bay Terminals...VFR. Onshore winds becoming light and variable
late tonight then southerly on Sunday. Light rain likely beginning
mid-late Sunday evening.

&& of 10:24 PM PDT Saturday...Generally light winds and
moderate seas across the waters through tonight. Gusty winds along
the inner waters south of Point Sur will diminish through tonight.
On Sunday, winds over the waters will increase and turn southerly
as a weak cold front approaches.


     .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm from 9 AM



MARINE: Anna/Canepa

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NWS MTR Office Area Forecast Discussion