Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
240 PM PDT sun Mar 29 2015
Synopsis...continued mostly clear and mild into Monday. A dry cold
front will pass through northern California by Tuesday and
Wednesday ushering in a noted cooling trend with highs mainly in
the 60s to middle 70s well inland along with gusty northwest winds
along the coast and in the hills. The trough will shift eastward
by the end of the week with a rebound in temperatures for Thursday
and Friday. Dry weather is forecast at least through Saturday.
Discussion...as of 2:40 PM PDT Sunday...its another sunny and
mild to warm afternoon across the Bay area with inland cities now
into the low 80s with plenty of 60s along the coast and 70s around
the Bay. Northerly gradient is still around 6 mb down the coast
and keeping the ocean free of stratus for the most part. There may
be some patchy fog along the San Mateo coast and around Monterey
Bay by morning but for the most part expect a clear and calm night.
No big changes in the weather for Monday but if anything
temperatures should trend a few degrees cooler by afternoon as
onshore flow gets more firmly re-established and 850 mb temperatures
start to cool slightly.
A fairly potent upper trough will move into the Pacific northwest
by Tuesday with a dry cool front and noted airmass cooling across
the Bay area and northern California. Highs on Tuesday mainly in
the 60s with perhaps some lower 70s with brisk winds off the ocean
and in the hills.
Seasonably cool and somewhat blustery winds will persist on Wednesday
with a strong surface pressure gradient across the state and a
cool upper trough aloft. It'll be a fitting start to the month as
April is often a windy time of year around here as cold upper
troughs pass over the region.
By Thursday afternoon the temperature trend should reverse with
the flow turning increasingly offshore and a thermal trough
developing along the coast. Initially the airmass aloft will be
cool so no dramatic warming is expected but skies should be
Crystal clear with no marine layer of note.
More noted warming should then be felt by Friday as the airmass
aloft begins to warm under riding with a thermal trough along the
coast through Friday morning.
The upper troughs that pass through far northern California this
week...although lacking little or no precipitation may actually signal
the beginning of a pattern change of note as the persistent West
Coast ridge retrogrades westward.
The pattern looks to stay dry next Saturday with seasonable
temperatures. By next Sunday a broad trough approaches the region
with increased confidence for some rain chances perhaps by next
Sunday or so. Long range models all more or less then drive a more
potent shortwave down the coast by around April 6-8th. For the
first time since perhaps last winter a more typical Gulf of Alaska
system may be in the cards. Its still over a week away so plenty
of room for error here. Pna teleconnection going negative with mjo
out into phase 3 along with with general agreement from Gem/GFS
and European model (ecmwf) puts confidence at least in the medium category this far out.
Aviation...as of 10:45 am PDT Sunday...generally clear skies
across the region this morning...aside from lingering stratus over
the Monterey Bay. Expecting VFR conditions to persist region- wide
with an increase in northwest winds this afternoon. Wind speeds
diminish this evening with possible return of low ceilings/visibilities early
Monday morning near the coast and around the San Francisco Bay up
through the North Bay.
Vicinity of ksfo...VFR. Northwest winds increase to the 12-20kt
range this afternoon with higher gusts through the late afternoon.
Wind speeds diminish late in the evening. Possible period of low
ceilings between 12z-16z Tuesday...yet confidence remains low.
Sfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR. Lingering low clouds should
remain west of the terminal over the next few hours before
clearing. West to northwest winds generally below 12kts to persist
through the afternoon. Low ceilings likely to return after 10z
Tuesday with lowering visibilities also possible around sunrise Tuesday
Marine...as of 02:03 PM PDT Sunday...strong and gusty northwest
winds will persist over the coastal waters today and into much of
next week as high pressure remains over the eastern Pacific. These
strong winds will produce locally steep fresh swells and short
... Pt to pt pinos 0-10 nm until 9 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 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...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Public forecast: rww
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