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

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000
FXUS66 KMTR 142336
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
336 PM PST Thu Dec 14 2017

...Breezy conditions likely late Friday through Sunday morning...
...Elevated fire danger particularly for higher elevation
locations for the same time...

.SYNOPSIS...Dry weather will continue into next week. A mainly
dry cold front will sweep south over the area late Friday night
and early Saturday morning which then increases N-NE winds along
the ridges and peaks Saturday.

&&

.DISCUSSION...as of 2:00 PM PST Thursday...Comfortable mid-
December weather conditions across our entire region today as a
moderate offshore flow at the surface is taking place while aloft
a strong ridge of high pressure remains along the coast.
Temperatures have warmed a bit above normal with many spots now in
the 60s to the lower 70s. Still have a couple hours of heating to
go, so those number will climb a bit higher. A few record highs
are definitely possible. Tonight will see another round of cool
temperatures due to light winds and mostly clear skies. Lows will
be in the mid 30s to the mid 40s in many spots.

After a few weeks of little synoptic change we will finally get a
break as a system drops down from the north and quickly moves
across our region late on Friday. Moisture associated with this
feature will stay to our north and west, so the main impact will
be breezy northerly winds that will greatly increase starting in
the afternoon. Various models remain in good agreement that gusty
winds will impact many higher elevation spots with the potential
of speeds exceeding 50 mph. At the same time dry air associated
with the frontal passage will help to lower humidity readings.
Saturday evening and night will see very dry air with some spots
not recovering above 10%. This has prompted a fire weather watch
to be issued which will likely be upgraded to a red flag warning.
A wind advisory has also been issued for the same locations.

Winds will diminish later on Sunday as the gradient both aloft and
at the surface starts to diminish. By Sunday night many spots will
be less than 10 mph -- even along ridge tops.

The ridge of high pressure will only partially rebuild for Monday
before flattening out in advance of the next system dropping down
from the north. By Wednesday it will move into Nevada with
another round of breezy northerly winds likely. Previous model
runs had been more bullish on precipitation moving through our
CWA, however latest thinking has backed off on that idea. Now
looks like the overall pattern will readjust with the ridge
farther to our west while dry, cold air dives in from the north.
Still no sign of widespread precipitation the next two weeks.

&&

.AVIATION...As of 3:35 PM PST Thursday...For 00z TAFs. VFR
conditions and mainly clear skies through the period with the
exception of patchy fog late tonight at KSTS. Onshore winds this
afternoon will become light and variable this evening.

High confidence.

Vicinity of KSFO...VFR. Light winds this afternoon and tonight.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. Onshore flow this afternoon around
10 kt decreasing this evening to become variable. Easterly winds
will pick up late tonight down the Salinas Valley at around 10 to
15 kt.

&&

.FIRE WEATHER...Due to a combination of very low humidity values
plus gusty winds, a fire weather watch is in effect for elevations
above 1000 feet from 10 PM Friday through 10 AM Sunday. The areas
of greatest concern are over the North and East Bay Hills where
local gusts will likely exceed 50 mph in places that will see very
poor humidity recoveries. This event is forecast to be weaker
than the one that produced the North Bay Fires in October, however
it does have the potential to create fires that rapidly grow.

&&

.CLIMATE...

Record high temperatures for Thursday, December 14, 2017.

SF BAY AREA                     December 14
.LOCATION................
 HEALDSBURG..............       77/1942
 SANTA ROSA..............       72/1956
 KENTFIELD...............       70/1942
 SAN RAFAEL..............       70/1959
 NAPA....................       73/1959
 SAN FRANCISCO...........       69/1988
 SFO AIRPORT.............       69/1958
 OAKLAND AIRPORT.........       65/1958
 RICHMOND................       67/1983
 LIVERMORE...............       75/1958
 MOFFETT FIELD...........       72/1958
 SAN JOSE................       73/1958
 GILROY..................       72/1988

MONTEREY BAY AREA
.LOCATION................
 MONTEREY................       78/1953
 SANTA CRUZ..............       82/1953
 SALINAS.................       80/1988
 SALINAS AIRPORT.........       81/1953
 KING CITY...............       83/1958

&&

.MARINE...as of 02:50 PM PST Thursday...Generally light to
moderate northerly winds will persist tonight and Friday over the
coastal waters. A cold front will push through the area late
Friday and will bring with it increasing northwest winds. Gale
force gusts will be possible across the outer coastal waters. Seas
will gradually increase through the end of the week and into the
weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...NONE.

&&

$$

PUBLIC FORECAST: Bell
AVIATION: AS
MARINE: CW

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