Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
123 PM PDT Friday Aug 22 2014
a trough of low pressure moving inland through the west will bring
stronger onshore flow through the weekend...with continued below
normal temperatures...gusty west winds in the mountains and deserts
during the late afternoon through late evening hours...and night and
morning stratus and fog into the western valleys. Increasing high
pressure aloft will likely bring warming next Tuesday through
Thursday...with weaker onshore flow...and shallower night and
morning stratus and fog mainly along the coast.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Marine layer stratus cleared out of the land areas...although it
took longer than expected...and now visible satellite shows
flat-looking cumulus over the mountains and also a little bit over
the Elsinore convergence zone. Aircraft soundings showed a weak
marine layer inversion at around 1600 feet above mean sea level this
morning. However...local WRF indicates the stratus moving in tonight
through tomorrow morning with better coverage into the western
valleys. As far as moisture GOES...GPS met sensors indicate
precipitable water continues to diminish in the area...decreasing to
around 0.8 inches near the coast...although the deserts still show
1.2-1.3 inches. Meanwhile...the 12z Miramar sounding showed a much
more stable atmosphere compared to yesterday...as the upper level
trough that moved through yesterday continues to move east over
Arizona. The increased stability and lowering amounts of moisture
means that we are unlikely to get thunderstorm activity forming over
the mountains and deserts today. With a relatively cool air mass
lingering over the area...day-time highs will remain several degrees
below normal today...except at the coast where they will be near
Current water vapor satellite indicates the aforementioned trough
over Arizona...a broad trough over the Pacific northwest...a ridge
over the northeast Pacific Ocean and Tropical Storm Lowell far to
the southwest of Southern California. The broad Pacific northwest
trough will move southeast into the inter-mountain west...and bring
dry westerly flow aloft to our region...with steadily increasing
surface onshore flow...through Monday. The marine layer may not
change too much in terms of its depth...so expect night and morning
stratus/fog into western valleys. Day-time high temperatures may not
change too much either...although there may be some slight warming
through that period...as models indicate some increase in 850 mb
temperatures. Regardless...high temperatures will still be several
degrees below normal in most locations. The increasing onshore flow
should also bring late afternoon and evening gusty west winds to the
mountains and deserts.
For Tuesday through Thursday...GFS and European model (ecmwf) indicate ridging
building over the region as the trough moves off to the east. This
should bring a warming trend...with temperatures reaching near to
slightly above normal for most places by Thursday. The ridge should
also bring a shallower marine layer...with night and morning
stratus/fog mainly along the coast.
222200z...coast/valleys...VFR conditions prevailing this afternoon.
Low clouds with bases 1200 feet mean sea level and tops 1900 feet mean sea level redeveloping
over the the coastal waters and moving inland up to 10 miles tonight
after 23/0600z. Visible will lower to below 3 sm where the cloud intersect
the terrain all the lower coastal slopes. These low clouds should
erode to the coast between 23/1500z-1700z.
Mountains/deserts...breezy southwesterly winds around 35 knots will
develop this afternoon and evening through mountain passes and along
adjacent desert slopes. Otherwise...mostly clear with few/scattered
cumulus clouds over mountain peaks this afternoon and unrestricted
visibility through Saturday morning.
100 PM...no marine weather hazards are expected through Tuesday.
an enhanced southerly swell will continue elevated surf and strong
rip currents at the beaches through this weekend. Surf to 8 feet are
expected in Orange County...with isolated sets to 7 feet forecast in
San Diego County. Highest surf will be along southerly facing
beaches. A beach hazards statement for San Diego County and high
surf advisory for Orange County is in effect through the weekend.
See laxcfwsgx for details.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...high surf advisory until 5 PM PDT Sunday for the beaches in the
Orange County coastal areas.
Beach hazards statement through Sunday afternoon for the beaches
in the San Diego County coastal areas.