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

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FXUS66 KMTR 240554

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1054 PM PDT Wed Aug 23 2017

.SYNOPSIS...Not expecting much change in weather conditions heading
into Thursday as temperatures remain slightly below seasonal averages
with overnight and morning low clouds. A warming trend will then
begin Friday and extend into early next week as high pressure builds
over the region. By Sunday and Monday, very warm to hot daytime
temperatures will be possible across inland areas.

&& of 8:03 PM PDT Wednesday...Summer onshore breezes
will usher stratus and fog inland tonight and Thursday morning. A
closed mid level and dry low that`s been gently meandering south
to north off SoCal and the Central Coast will finally be moving
eastward as a trough upstream to the northwest moves closer toward
California. Marine layer moisture will tend to turn into patchy
drizzle on the immediate coastline tonight as outlined in the
grids/zones. The 18z NAM indicates very light qpf amounts along
the coast tonight and Thursday morning, otherwise our typical
summer dry stretch will continue. Current forecast outlines a
gradual warming trend for late week as high pressure builds over
California coupled with a return of long-wave ridging. Forecast
looks good, for more details please visit the previous discussion


.PREV of 1:35 PM PDT Wednesday...A weak short-wave
trough and associated low pressure system remains off of the
central and southern California coast today. This has helped to
maintain a modest marine layer of around 1,500 feet in depth.
While low clouds will burn-off over inland areas and mainly
retreat to the coast, stratus will again return to coastal areas
and adjacent valleys overnight with the chance of patchy fog and
drizzle as the marine layer becomes more compressed. Little
overall change is forecast into Thursday afternoon with inland
temperatures remain on the cool side of normal while coastal areas
warm into the 60s and 70s.

The aforementioned trough is forecast to dissolve by Friday as high
pressure over the Desert Southwest builds westward. This will work
to further compress the marine layer and result in less widespread
cloud cover, especially across the inland valleys. In addition,
temperatures aloft will warm and bring about warmer temperatures
across inland areas. As the ridge strengthens aloft, surface
temperatures will continue to warm through the weekend with more
widespread 80s and 90s inland with our warmer locations likely to
exceed the 100 degree mark by Sunday. In addition, overnight lows
will not cool as much, especially in the hills where temperatures
may only cool into the 70s. With this, the threat for heat related
illnesses will increase by Sunday into Monday given the hot daytime
temperatures and limited overnight cooling. Meanwhile, coastal areas
will notice a warming trend yet will continue to benefit from the
cool onshore flow. Will closely monitor the need for any heat
related products heading into late week with regards to the
Sunday/Monday timeframe.

The ridge looks to remain the dominate weather feature heading into
much of next week as well. With that said, the ridge does appear to
weaken slightly and shift a bit more inland by the middle of next
week. With this, do expect the peak heating to occur Sunday into
Monday with a slight cooling trend by the middle of next week.
Temperatures will likely rebound back closer to seasonal averages
along with continued dry weather conditions through the entire
forecast period.


.AVIATION...As of 10:54 PM PDT Wednesday for 06Z
TAFs...Widespread coastal stratus has moved in through coastal
gaps and canyons under a 2000 ft marine layer. Clearing to the
coast is anticipated around 17z Thursday morning. Light winds.

Vicinity of KSFO...Borderline MVFR/IFR cigs and vsbys anticipated
to prevail through tonight. Light west winds will persist through

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...IFR cigs will prevail through tonight
with decreases vsbys overnight into the morning hours. Light

&& of 9:00 PM PDT Wednesday...Northerly winds will
continue to increase through the evening and overnight as high
pressure builds to the west. Expect these winds to persist over
the waters through the end of the week. No significant long period
swell is forecast through the rest of the week.


     .Tday...SCA...Mry Bay from 9 AM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 AM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...SF Bay from 1 PM




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