Area forecast discussion
National Weather Service San Francisco Bay area
325 am PDT sun may 19 2013
Discussion...as of 03:15 am PDT Sunday...mostly cloud free
across the area this morning except for patches of developing
stratus along the San Mateo and Monterey coasts. As a shortwave
moved across Oregon into Nevada over the past 12 hours the
northerly gradient has tightened...strengthening northwest winds
over the waters and keeping the marine layer from moving inland.
Clouds that do develop along the coast will likely burn off
quickly after sunrise this morning and skies remain clear into at
least Monday evening.
An upper ridge will build over the region the next couple of days
and onshore flow will decrease bumping surface temperatures upward.
The ridge tilts over the state Monday bringing 850 mb
temperatures into the upper teens. Winds veer north overnight
Sunday into Monday which will cause warm offshore flow. Combining
with the warm airmass...Monday will be the warmest day of the
week. Coastal locations such as Point Reyes are forecast to reach
70 f while inland temperatures push into the upper 90s. Most
locations will be upwards of ten degrees above normal highs.
The north winds Sunday night into early Monday morning will be
moderately strong over the north and East Bay hills. The warm dry
winds will cause enhanced fire danger however they will be
confined to a limited area and rapidly diminish Monday. No red
flag warning is expected and plan on maintaining headline in the
forecast.
The warming trend comes to an abrupt end early in the week. An
upper low dropping south out of the sub Arctic reaches the state
Tuesday. Just how dramatic The Drop off on Tuesday will be will
depend on just how early in the day the cooler air moves in.
Currently looks like all but the southern reaches of the County Warning Area will
experience a decrease of at least 10 degrees over Monday highs.
Temperatures continue to cool Wednesday as the trough digs
further south.
The low center will reach as far south as Oregon late
Tuesday...far enough away to keep all precipitation north of the
district. The trough stays fairly persistent through the work week
which will maintain below normal temperatures...particularly
inland. Sunny skies will prevail most of the week as significant
marine layer development will be inhibited.
In the longer term models agree on the upper low lifting out of
the Pacific northwest Saturday but there is disagreement on the
continued presence of a trough over the West Coast. Latest European model (ecmwf)
deterministic run still has zonal flow develop by Saturday while
latest GFS and ensemble means of both models keep some weak
troughing over the region through Memorial Day weekend. For now
the area looks to stay cool through at least the first half of the
weekend.
&&
Aviation...as of 10:30 PM PDT Saturday...increasing northerly
gradients will keep stratus to areal coverage tonight. Thus only
brief ceilings are expected in the sfo Bay area Sunday morning.
Vicinity of ksfo...brief MVFR ceilings possible between 12z and 16z.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...MVFR ceilings through 17z.
&&
Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...mry Bay from 1 PM
&&
$$
Public forecast: ac
aviation/marine: west pi
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