Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
850 am PDT Monday Sep 22 2014
a building ridge of high pressure aloft will bring warmer weather
through midweek...as inland temperatures rise to 5-10 degrees above
average. The inland extent of night and morning low clouds will also
shrink...becoming confined to the immediate coast by Wednesday
morning. A deepening trough of low pressure along the West Coast by
Friday will bring breezy and cooler weather with a deepening marine
layer into the weekend...accompanied by gusty winds in the mountains
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Autumn begins tonight at 729 PM PDT.
The marine stratus was dramatically reduced this morning as the
marine inversion was cut in half from yesterday. The 12z Miramar
sounding had the base of a 6 degree c inversion near 1700 feet. A southeast
flow of 10-20 kts had developed above the inversion to around 9k
feet...but precipitable water remained very low at 0.74 inch. Surface pressure
gradients were weakly onshore to the deserts.
The weather will be dry and warmer through Wednesday as high pressure
builds aloft. Models agree the high will peak over the region at 592
dm before sliding off to the NE Wed/Thu. Heights and thickness will
remain elevated over the region into Friday as a trough digs south
along 130w. This will keep the marine layer rather shallow with
limited marine clouds...but possibly more fog as moisture becomes
concentrated in the boundary layer and the longer nights allow more
cooling. Daytime highs will gradually lower again Thursday through Sat.
There remain considerable differences in the latest model solutions
regarding the trough later in the week. The GFS models is the most
progressive...while the European model (ecmwf) cuts off the system and holds it back
over California through Sun morning. The Gem seems to split the
difference...but drags the closed low a little farther south. No
model generates precipitation this far south...so the best we can hope for
at this time is a different outcome...or perhaps some marine layer
drizzle one morning.
Other than the cooling...the main weather element from the trough
will be gusty onshore winds. Advisory strength looks possible at
some point Friday or Sat over the mtns/deserts. Behind the trough it
will be warmer early next week with temperatures about average for
late Sep/early Oct.
221530z...areas of low clouds over portions of the coastal areas and
San Diego County valleys...otherwise clear with unrestricted visible
this morning. Bases are around 1500 feet mean sea level with tops around 2000 feet
mean sea level. Ksna may be affected for brief periods before 17z...but
confidence is not high. Most areas will clear by 17z. Low clouds
will return to coastal taf sites after 06z Tuesday with ceilings a few hundred
feet lower and less inland extent. Otherwise...mostly clear through
900 am...no hazardous marine weather is expected through Friday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.