Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
910 am PDT Monday Apr 27 2015
Synopsis...strengthening high pressure will bring warm and dry
conditions to the entire area today. A dry cold front will approach the
coast by Tuesday...resulting in increasing onshore flow and a
modest cooling trend Tuesday and Wednesday. Dry and seasonable
weather is then forecast from Wednesday through the upcoming weekend.
Discussion...as of 9:15 am PDT Monday...sunny start to the day
with most places 4 to 8 degrees ahead of yesterday. Koak sounding
shows as much as 10c of warming up to 900 mb so good potential for
much above normal readings today. Also of note is sfo-SAC has
dropped to around neutral which will help to warm coastal spots.
Highs will range from the 60s and 70s down to the ocean up to middle
70s to upper 80s well inland.
No major updates planned this morning.
Previous discussion...skies are mostly clear across the entire
region early this morning as an upper ridge builds directly over
the Golden state. The Fort Ord profiler shows that subsidence
warming under this ridge has warmed the airmass aloft by as much
as ten degrees c over the past 24 hours. Also...surface pressure
gradients down the coast from acv to sfo have been increasing
while gradients from the coast to inland areas decrease. All of
these developments point to a warmer day today across the
region...with afternoon highs expected to be 5 to 10 degrees
warmer than yesterday and as much as ten degrees...or more...above
Today will be the warmest day of the week for most locations. The
models have consistently forecast the upper ridge to move off to
our east by Tuesday...while an upper trough over the eastern
Pacific approaches the northern California coast. All of the moisture with
this trough...and most of the cold air as well...will lift well to
our north prior to reaching the California coast. The trough
will...however...produce an increase in onshore flow and modest
cooling Tuesday and Wednesday. Cooling on Tuesday and Wednesday
will primarily be near the coast and in the northern interior
sections of our forecast area. Southern inland areas will see
The GFS develops upper level ridging off the northern California coast by
Thursday and Friday as well as light offshore flow...and thus
forecasts warmer temperatures later in the week. The European model (ecmwf)...on the
other hand...forecasts a piece of energy from the midweek system
to hang back off the California coast as a weak upper low.
Thus...the European model (ecmwf) holds temperatures near persistence from Wednesday
through Friday. The Canadian has aspects of both of these
solutions...but favors the GFS. For now have gone ahead and
forecast modest warming late in the week.
No big changes are forecast going into the upcoming weekend. Dry
weather is expected to persist along with slightly above normal
Aviation...as of 4:35 am PDT Monday...a robust 5 mb northerly
gradient from acv-sfo will maintain mainly clear skies across
the region through late tonight. Light west winds will persist
through this morning then increase this afternoon. Moderate west
winds are expected through this afternoon and evening. High
Vicinity of ksfo...VFR conditions expected through late tonight.
Light winds will increase this afternoon with sustained winds out
of the west between 13 and 18 knots. Winds will ease after 05z this
evening. High confidence.
Sfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR conditions expected through late
tonight. Light winds will increase this afternoon with sustained
west winds around 12 knots expected. Winds will gradually ease this
evening. High confidence.
Marine...as of 09:06 am PDT Monday...high pressure will maintain
moderate northwesterly winds across the coastal waters through
tonight. Winds are anticipated to strengthen midweek as a cold
front pushes towards the California coast. Strong winds will
persist through the end of the week as the frontal system moves
across the region.
... Bay north of the Bay Bridge from 2 PM
Small Craft Advisory...sf Bay south of the Bay Bridge from 2 PM
Small Craft Advisory...Monterey Bay from 2 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm from 2 PM
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm from 6 PM
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm from 6 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 6 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm from 2 PM
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 2 PM
Public forecast: Bell/dykema
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