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Area forecast discussion 
National Weather Service San Francisco Bay area
143 PM PDT Tue Oct 25 2016

Synopsis...rainfall will continue to diminish in coverage over the
North Bay this afternoon with dry weather likely region-wide on
Wednesday. Our next weather system will bring widespread
rainfall,locally heavy at times, to just about all on Thursday as an
upper level low approaches the central coast. Showers will linger on
Friday with yet another storm system set to impact the region from
Saturday afternoon into Sunday.

&& of 01:42 PM PDT Tuesday...light to occasionally
moderate rain continues over the North Bay this morning as
moisture associated with a washed out frontal boundary shifts
northward into northern California. This has resulted in drying
conditions from the South Bay down through the central coast where
some breaks in cloud cover can be see on visible satellite. This
trend will continue with rainfall diminishing in coverage through
the evening and becoming limited to the far northern portions of
the North Bay tonight.

Mostly dry conditions are expected region-wide on Wednesday ahead of
our next approaching system that will arrive on Thursday. Forecaster
confidence continues to increase that Thursday will be wet region-
wide as an upper level low approaches the central coast. This system
will tap into a much deeper plume of moisture with precipitable water values in
the 1.40" to 1.70" range (deepest moisture advection may be just to
our south). At this time, have kept a mention on thunderstorms out
of the forecast, yet cannot rule out a slight chance as the main
mid/upper level low nears the coast Thursday afternoon/evening. Will
monitor the latest forecast guidance in the next 24 hours or so to
see if thunderstorms need to be added to the forecast. This system
will result in widespread rainfall beginning early Thursday morning
with the bulk of the precipitation to occur during the daytime
hours. Rainfall amounts along on Thursday will likely range from
0.50" to 1.50" for most urban and coastal locations (even for
the typical rain-shadowed valleys) with 2.00" to 3.00" amounts over
the hills and coastal ranges. Given the deep moisture tap, cannot
rule out locally greater rainfall totals within any heavier rainfall
bands that develop.

As the aforementioned mid/upper level low shifts inland, widespread
rainfall will tapper off Thursday night into Friday with only
lingering showers/rain possible on Friday. Precipitation amounts
will likely be on the low side from Friday night into Saturday ahead
of yet another mid/upper level system. As this storm system pushes
inland to our north, a frontal boundary will push southward across
the region Saturday afternoon into Sunday morning. With that said,
confidence remains lower on timing of the system and rainfall
amounts. Then, lingering precipitation will be possible through
Sunday and potentially into Monday.

An active, unsettled weather pattern looks likely to persist heading
into next week as well with temperatures near or below seasonal
averages. If you have any plans late in the forecast period, be
sure to stay tuned for the latest updates.

&& of 10:45 am PDT Tuesday...VFR cigs with isolated
showers moving through the area. Showers will decrease today as
the frontal system pulls north out of the area. Southeast winds
12-18 kt will shift to more southerly in the afternoon but remain
gusty around the San Francisco Bay area.

Vicinity of ksfo...VFR. Southeast winds 15-18 kt shifting more
southerly in the afternoon with gusts to 20 kt. MVFR cigs after

Sfo bridge approach...similar to ksfo.

Monterey Bay terminals...VFR with rain and low clouds staying north
of the mry Bay area. MVFR cigs after 03z.

&& of 8:31 am PDT Tuesday...Small Craft Advisory
conditions for hazardous seas will be across the coastal waters
today. Light south winds are expected today then increase briefly
on Wednesday before decreasing on Thursday. Another low pressure
system is expected to impact the coastal waters Friday and


Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Arena to Pigeon pt 10-60 nm
Small Craft Reyes to Pigeon pt 0-10 nm until 9 PM
Small Craft Advisory...rough bar advisory for sf bar until 3 am



Public forecast: rgass
aviation: Sims
marine: Sims

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