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Area forecast discussion 
National Weather Service San Francisco Bay area
1053 PM PDT Monday Sep 29 2014

Synopsis...a weak weather system will brush across northern
California Tuesday bringing onshore flow tonight and Tuesday. High
pressure will build along the coast from midweek through the end
of the week and offshore flow will develop. Look for warmer and
drier conditions Wednesday through at least Friday. Slight coastal
cooling is possible over the weekend while inland areas remain very
warm.

&&

Discussion...as of 8:05 PM PDT Monday...a short wave swinging
across northern California this evening will bring increasing high
clouds to the region as well as stronger onshore flow across the
district tonight and Tuesday. Low clouds are expected to move
inland again overnight but similar to yesterday will be
disorganized and broken in nature.

Temperatures on Tuesday will be within a few degrees of today's
highs with clearing of the low clouds expected around noon.

A distinct pattern change is expected midweek as high pressure
builds over the region. 850 mb temperatures and 500 mb heights will rise
steadily beginning Wednesday with temperatures rising to near 20c and
heights reaching 590 dm by weeks end. Along with a warmer airmass
winds are expected to turn offshore which will result in drier
conditions across the area. Strongest offshore wind are expected
to develop Tuesday night across the north and East Bay. Gusty
north to northeast winds in excess of 30 miles per hour are expected over
higher elevation. Relative humidity values are expected to begin steadily
decreasing Tuesday night which will increase the fire danger
across the district.

Temperatures are forecast to begin warming Wednesday and will
continue warming through the end of the week. Warm temperatures
are also expected to reach the coast as offshore flow persists.
Warmest temperatures are expected Friday with 80s and 90s scattered
across the Bay area. A few 100's are also expected over the
warmest southern interior valleys.

From previous discussion...still uncertain how this pattern will
break down. European model (ecmwf) and Gem hint at possible southerly surge over
the weekend...but GFS increases coastal humidity under northwest flow.
European model (ecmwf) progresses the ridge inland early next week and implies
strengthening onshore flow. Gem and GFS a little slower
progressing and weakening the ridge. In any case...looks like
several days of above normal temperatures and dry conditions.
Onshore flow should return in the afternoons near the coast over
the weekend...bringing some cooling. Long range guidance in the 8
to 14 day period calls for dry and warmer than normal conditions
to continue.

&&

Aviation...as of 10:55 PM PDT Monday...patchy clouds across the
area this evening with some terminals dropping down to MVFR
levels. Difficult forecast with the guidance suggesting low ceilings
almost all night at all spots which the satellite (and stronger
northerly gradient) suggesting that we could see frequent breaks
overnight. Will go mostly with model guidance but changes may need
to be made by the middle of the next shift if it is not working
on. Only fair confidence for tonight into the morning hours.

Vicinity of ksfo...1 minute ob have gone back to scattered after a
period of bkn018. Satellite shows just patchy clouds around and
upstream so a big hesitant to completely believe the model
guidance which brings in MVFR for much of the night. Do feel
confident that tonight will be the final potential for low clouds
as the flow GOES more offshore. Only fair confidence.

Ksfo bridge approach...so far clouds have stayed out of the
approach and appears it may end up filling in after the terminal.

Monterey Bay area terminals...clouds confined to the coast so far
just impacting kmry. Should see an increase with low clouds to
ksns by 08z. Generally west winds under 10 knots. Moderate
confidence.

&&

Marine...as of 10:55 PM PDT Monday...northwest winds will continue
to increase tonight through Tuesday morning in wake of a weak
frontal passage. High pressure will then build into the coastal
waters through middle week...maintaining moderate to occasionally
strong wind speeds and building seas. Winds will then diminish by
late week as surface high pressure weakens.

&&

Climate...record high temperatures for Wednesday through Friday
(10/1 to 10/3) along with the most recent date it occurred.

Sf Bay area
location.................10/1...........10/2............10/3...
Kentfield................97/2012.......100/2012.........99/2012
San Rafael..............104/1980.......106/1980........105/1980
Napa....................106/1980.......102/1980........103/1917
San Francisco............97/1980........96/1980.........97/1985
sfo Airport..............97/1980........96/1980.........94/1985
Oakland (downtown)......103/1980.......103/1980........100/1985
Oakland Airport..........94/1952........98/1980.........95/1985
Richmond.................99/1980.......100/1980.........97/2012
Livermore...............102/1952.......106/1980........106/1980
Moffett field............93/1980........95/2012.........97/1985
San Jose.................97/1980........96/2012.........97/1985
Gilroy..................104/2001.......107/1980........106/1980

Monterey Bay area
location.................10/1...........10/2............10/3...
Monterey................103/1980.......101/1980.........96/1985
Santa Cruz..............102/1965.......102/1980........102/1980
Salinas.................104/1980.......100/1980.........97/1985
Salinas Airport.........105/1980.......103/1980.........99/1985
King City...............109/1980.......107/1980........102/1980

&&

Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm from 3 am
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm from 3 am
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm

&&

$$

Public forecast: CW
aviation/marine: Bell
climate: Bell

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