Area Forecast Discussion
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FXUS66 KMTR 042153
Area Forecast Discussion
National Weather Service San Francisco Bay Area
153 PM PST Sun Dec 4 2016
.SYNOPSIS...A mainly dry cold front will approach northern
California Monday and Tuesday with seasonably cool temperatures.
There will be a slight chance of showers on Tuesday with the
front. Wednesday morning may be the coldest morning so far this
season with inland valleys around 30 degrees. Warm frontal rains
will be possible later Thursday into Friday.
.DISCUSSION...as of 1:53 PM PST Sunday...Some high clouds over
the Bay Area this afternoon with afternoon highs in the upper 50s
to around 60. The high clouds will keep overnight lows from
dropping too much as a mainly dry cold frontal boundary pushes
into northern California. Daytime highs will cool into the mid 50s
for Monday with high clouds and a cooler air mass in place.
A secondary cold front/short-wave will drop down on Tuesday with
steady rains confined to north of Cape Mendocino. There may be
just enough moisture and cold instability aloft to generate some
isolated showers across the area on Tuesday so slight chance pops
have been expanded for the Tuesday time frame. Any qpf with these
will be light and widely scattered in nature.
The coldest airmass of the season will be left in the wake of that
boundary and overnight lows by sunrise Weds morning could be the
coldest so far this season. Still a few days out so will hold off
on any frost/freeze type headlines as the leftover low clouds or
incoming high clouds could limit the amount of cooling.
Brief ridging will return on Wednesday with highs in the 50s as
high clouds begin to increase ahead of a warm advection pattern.
Confidence is increasing for warm advection rains to develop later
Thursday into Friday as a pacific jet approaches the region.
Early qpf numbers from the rfc shows 1-2.5 inches of rain
potential but at this time the best chances look to be focused
from the north bay southward to the Santa Cruz Mtns. Still a lot
of time to sort out timing and rainfall totals with this event but
the ecmwf has been consistent for at least the last four model
runs. With no strong cold advection not expecting heavy rain rates
but rather a prolonged period of soaking light to moderate rains
sometime later Thursday into Friday.
Low confidence beyond that with some type of break likely Friday
night into Saturday but then the models diverging on possible
continued systems later next weekend or early next week. Either
way no blocking ridges in sight and a nice moderately active start
to the rainy season.
.AVIATION...As of 10:00 AM PST Sunday...VFR through the day due
to offshore flow at the surface. Moisture will return tonight as a
system approaches from the north. This will lead to MVFR CIGs
returning to portions of our region. High confidence through 04Z
with moderate confidence after that.
Vicinity of KSFO...VFR through 05Z with the potential for MVFR
conditions after that point. Winds generally 280 to 300 through
the day with speeds up to 15 KT. High confidence through 05Z.
Moderate confidence after that.
SFO Bridge Approach...Similar to ksfo.
Monterey Bay Terminals...VFR through 05Z with IFR CIGs expected
after that point. Winds mostly 280 to 300 up to 10 KT. High
confidence to 03Z. Moderate confidence after that.
.MARINE...as of 01:38 PM PST Sunday...Moderate northwesterly winds
will continue over the next several days. in addition...northwest
swell will gradually subside going into the work week.
.Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Rough Bar Advisory for SF Bar until 3 AM
PUBLIC FORECAST: RWW
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