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

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FXUS66 KMTR 240335
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
835 PM PDT Sun Jul 23 2017

.SYNOPSIS...Cooling is forecast for Monday and Tuesday due to a
deepening marine layer and increased onshore flow. Warming is then
expected during the second half of the week as an upper ridge
builds back across California. Aside from some possible coastal
drizzle during the next few nights/early mornings, no
precipitation is presently expected in our area through the
forecast period.

&&

.DISCUSSION...as of 8:35 PM PDT Sunday...Visible satellite
imagery just before sunset reveals a widespread stratus deck along
the coast associated with a marine layer about 1,000 ft deep. The
experimental and non-operational GOES-16 satellite is even able
to clearly capture the stratus pushing through the Golden Gate.
Expect the cloud coverage to increase through the night for
coastal communities.

The San Francisco Bay Area`s many microclimates were in full
force this afternoon with highs ranging anywhere from the 50s and
60s near Half Moon Bay to the triple digits for some interior
East Bay cities. Concord`s 100 degree high this afternoon was its
11th triple digit day observed this year. Over the short period
of record at Concord`s Buchanan Field KCCR (1999 to present), 2017
ranks first for the most triple digit days year-to-date. Today
should be Concord`s last 100 degree reading for the short-term as
an approaching upper-level low will allow for appreciable cooling
for much of California through Tuesday. As mentioned in the
previous discussion, models are advertising a strong ridge to
build over Nevada by the weekend and into the early part of next
week. This would translate to well above normal temperatures with
the potential for very hot weather across inland areas. Stay
tuned for more details...

No changes planned for the forecast this evening. For additional
details, please refer to the previous discussion.

&&

.PREV DISCUSSION...As of 2:00 PM PDT Sunday...GOES16 shows clouds are
just hugging the immediate coastline with clear skies across the
rest of our region. Temperatures have moved back to values close
to what we saw yesterday -- warm to very warm inland with cooler
conditions near the coast. Warmest readings for far interior spots
are in the 90s with a few lower 100s likely before the end of the
day. Tonight should quickly bring back clouds from the coast to
lower elevation spots. However, it will likely deepen as an upper
level low and shortwave trough near our region. Look for upper 40
to upper 50s in urban spots with 60s to lower 70s in many higher
elevation areas. Patchy drizzle will be possible mainly at the
coast.

Temperatures will be cooler on Monday and Tuesday as the upper
level low and trough move overhead. Overall flow will also become
more pronounced from the west which will also allow for cooler
conditions. Highs will generally be 5 to 10 degrees cooler away
from water with less of a drop at other spots. Clouds are likely
for the overnight hours.

A ridge will rebuild into our region over the second half of next
week into the following week. Long range guidance off the ECMWF
and GFS are both showing a very strong ridge centered across
Nevada by the first of August. Values are forecast to be around
600 DM at 500 MB suggesting the potential for very hot weather.
CPC 6 to 10 and 8 to 14 day guidance also favors above normal
readings.

&&

.AVIATION...as of 4:30 PM PDT Sunday...Southerly flow along the
coast will bring stratus into the MRY Bay Area early tonight and
into the North Bay late. Stronger winds blowing through the
Golden Gate will push stratus into OAK and the East Bay but the
airmass is warm enough that the stratus will hold off getting into
OAK until after midnight. However southerly flow keeps stratus
out of SFO although it is possible for tempo cigs early in the
morning.

Vicinity of KSFO...Maintaining VFR. West to northwest winds to 20
kt through 04Z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...IFR cigs into SNS after 02Z spreading
into MRY after 04Z.

&&

.MARINE...as of 08:16 PM PDT Sunday...Generally light winds will
continue tonight over the coastal waters. As surface low pressure
develops off the coast of Point Reyes Monday morning, winds will
become southerly, for waters south of the low, but remain light to
moderate. Westerly winds will continue to remain gusty through
the Golden Gate gap, and near Angel Island, during the afternoon
and early evening hours over the next few days. Seas will continue
to be small with a longer period southerly swell mixed in at
times.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...SF Bay until 11 PM

&&

$$

PUBLIC FORECAST: Rowe/Bell
AVIATION: W Pi
MARINE: BAM


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