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

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FXUS66 KMTR 232339

Area Forecast Discussion
National Weather Service San Francisco Bay Area
439 PM PDT Fri Mar 23 2018

.SYNOPSIS...A cold weather system approaching from the north will
bring renewed chances of rain starting in the North Bay today,
and across the remainder of the area tonight and Saturday
morning. Additional shower activity is possible Saturday afternoon
through Sunday morning. Dry weather is expected to return to most
areas by Sunday afternoon and continue well into next week.

&& of 01:48 PM PDT Friday...Most of the Bay Area is
significantly drier and experience more sunshine today than
Thursday. That being said, an approaching low pressure system from
the north continues to produce cloudy conditions with scattered
showers across the North Bay. Latest radar imagery shows widely
scattered showers passing through the North Bay. Automated gages
have reported a few hundredths to a much as 0.12".

Expect showers to continue across the North Bay this evening and
gradually spread southward as weak cold front moves through the
region. Latest model guidance has the cold front bisecting SF Bay
Saturday morning around 12z and then moving farther south through
the day. Compare to recent storms this system will feature much
less moisture and cold temperatures. Snow levels will generally be
above 3k feet then gradually drop behind the front on Saturday.
The cold air aloft from the north will help to destabilize the
atmosphere on Saturday afternoon with daytime heating. There will
be a slight chance 15-20% chance for thunderstorms across the
North Bay.

Another weak surface boundary will be quick on the heels of the
cold front keeping lingering showers through early Sunday.
Rainfall amounts from today through Sunday will be generally be
0.25-0.5" North Bay (locally higher in the mts), 0.10-0.25"
elsewhere, except <0.1" interior Monterey/San Benito. Snow
accumulations will be tricky given the showery nature, but a
dusting to minor accumulations will be possible over the peaks.
Impacts from snow will be minimal.

The Bay Area finally begins to dry out late Sunday into Monday
with a gradual warm up. Latest medium range models show ridging
over the West with warming daytime temps. Max temps next Tuesday
and Wednesday will be in the 70s for much of the region, which is
well above normal for late March.


.AVIATION...As of 04:39 PM PDT Friday...for 00Z TAFs. Currently
VFR conditions at all sites with scattered clouds and occasional
showers in the North Bay. A cold front is still expected to move
through late tonight bringing another round of steady showers. As
the front approaches expect cigs to begin to lower back to MVFR.
Shower chances will end early tomorrow morning once the front has
passed and VFR conditions should once again prevail.

Westerly winds will remain breezy through the evening at around 15
kt before taking a more southerly turn and somewhat decreasing.

Vicinity of KSFO...VFR anticipated through about 03z or so, with
FEW/SCT clouds between 3,000 to 5,000 ft AGL. Cigs expected to
lower to MVFR this evening, ahead of a cold front that is forecast
to pass through the terminal around 08-11z tonight. Models still
suggest a narrow band of rain as the cold front sweeps through.
Left a few hours of light rain in the tafs. Breezy southwesterly
winds expected to continue into tonight.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR conditions through tonight. Cigs will
lower after midnight tonight, ahead of an approaching cold front
forecast to pass through early Saturday morning. Expect wet
runways from light rain as the front passes. Breezy westerly winds
will continue into the evening.

&& of 02:33 PM PDT Friday...Light to moderate west or
southwest winds will prevail this evening. A series of cold fronts
pass over the coastal waters and bays, starting overnight
tonight. Light rain is possible along the cold front tonight, with
winds turning northwest behind it. Another cold front will pass
over the waters Saturday evening into Sunday morning. Northwest
swell will increase slightly overnight tonight.


     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...SF Bay from 9 PM until 3 AM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM until 3 AM




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