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fxus66 kmtr 171129 
afdmtr

Area forecast discussion
National Weather Service San Francisco Bay area
329 am PST sun Nov 17 2019

Synopsis...a gradual warming and drying trend will continue through
the remainder of the weekend as high pressure builds over the
region. Cooler conditions will develop Tuesday and Wednesday as a
weather system drops in from the north. Little or no rain is
expected with this system. Gusty north to northeast winds are
possible in the north and East Bay hills from Tuesday night
through Wednesday night. Dry conditions, along with seasonable
temperatures, are forecast from Thursday through next weekend.

&&

Discussion...as of 3:15 am PST Sunday...primary short-term
concern is the possibility of dense fog this morning. Fog is much
less extensive at the present time compared to early yesterday
morning, thanks to light offshore flow mixing drier air into the
boundary layer yesterday. Current surface dewpoints are anywhere
from 2 to 11 deg f lower than 24 hours ago. Thus, it's expected
there will be only patchy dense fog this morning, mainly near the
ocean.

Another short-term concern involves locally dry and gusty north
winds in the hills. Winds are currently gusting between 35 and 45
mph above 4000 feet on Mount Saint Helena, and overnight humidity
recovery has been poor in the hills. However, heightened fire
weather concerns are primarily limited to only the highest peaks
of the North Bay. Winds elsewhere are generally not as much of an
issue with only local gusts up to about 20 mph. Winds in the hills
are forecast to gradually subside through today.

Subsidence warming under a strong upper ridge continues to warm
the airmass over our area. This, and the fact that many areas
will see more sun today due to lack of morning fog, will mean
warmer temperatures. Afternoon highs today will range from the
upper 60s to lower 80s and be anywhere from 5 to 15 degrees warmer
than normal. The upper ridge is forecast to begin weakening on
Monday and light onshore flow is expected to develop by late
afternoon. But these developments likely won't happen soon enough
to have much impact on monday's temperatures. Highs tomorrow are
expected to be similar to today across inland areas, with perhaps
a few degrees of cooling near the coast.

An upper trough will develop over the Pacific northwest by late
Monday and then split, with the southern portion of the split
forecast to dive south over California on Tuesday, eventually
forming a closed upper low over Southern California by Wednesday.
As the trough digs south across our area from late Tuesday through
early Wednesday, it may trigger a few isolated light showers. But
the system will be lacking significant moisture until after it
reaches Southern California. Thus, most of our area should remain dry at
midweek. The primary impacts this system will have on our area
will be to cool our temperatures back to near normal on Tuesday
and also produce locally gusty north to northeast winds after it
passes to our south. Strongest winds are expected in the hills of
the sf Bay area from Tuesday night through Wednesday night. The
latest NAM forecasts 45 knot 925 mb winds across the North Bay at
12z Wednesday. Although the airmass will be relatively cool, it
is also expected to be quite dry and the combination of gusty
winds and low humidity may result in critical fire weather
conditions around midweek, mainly in the hills of the north and
East Bay. Also, lack of wetting rains will likely mean fuels will
remain near record dry levels for this time of year. Will need to
consider issuance of a Fire Weather Watch if models continue to
predict dry, gusty offshore winds at midweek.

Winds in the hills are forecast to subside by Thursday as the
upper low to our south moves east. Although there are some
differences in model solutions late in the week, the general idea
is that dry conditions, along with seasonable temperatures, can be
expected from Thursday on through next weekend.

&&

Aviation...as of 03:29 am PST Sunday...for 12z tafs. A shallow
marine layer remains in place, but with drier conditions over land
there has been a delay in fog development compared to last night.
VFR conditions currently but the possibility of patchy fog
developing around sunrise remains. VFR prevailing with patchy fog
until around 16z. Light winds this morning turning onshore for
coastal sites this afternoon at around 10-15 kt with offshore
winds inland.

Vicinity of ksfo...VFR with light winds becoming onshore this
afternoon. Fog is looking less likely this morning, but still a
possibility until around 16z. Low confidence.

Sfo bridge approach...similar to ksfo.

Monterey Bay terminals...patchy fog earlier this evening has
since mostly cleared out. VFR prevailing with patchy fog
possible until 16z. Generally light winds through the period.

&&

Marine...as of 2:03 am PST Sunday...light to moderate northwest
winds will persist across the coastal waters through the rest of
the weekend and into Monday with locally breezy winds over the
northern outer waters. Northerly winds will then increase across
the waters on Tuesday as an upper level system moves through and
remain moderately strong and gusty through mid-week. Northwest
swell will continue to subside tomorrow before re-building late
Tuesday night. The combination of gusty winds and building swell
will generate hazardous seas conditions early to mid-week.

&&

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

&&

$$

Public forecast: dykema
aviation: as
marine: as

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