Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
851 am PDT sun Sep 21 2014
low pressure aloft will begin to exit the region later today as high
pressure builds from the south. This will lower our unseasonably
deep marine layer for less extensive night and morning low clouds
west of the mountains through Wednesday. Daytime highs will be near
average for late September today...then gradually warm to 5 to 10
degrees above average by midweek. Much cooler for the end of the
week as a deep trough develops across California...bringing rain to
northern portions of the state...and blustery...autumn-like weather
across the Southland.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Weather trends this week...progressively less extensive marine
cloudiness but more fog west of the mountains Tuesday through
Thursday...a warming trend beginning Monday...bringing temperatures
back above average through midweek...much cooler weather by next
Once again this morning...marine layer stratus was extensive west of
the mountains...extending along the lower coastal slopes. The 12z
Miramar sounding this morning had a 5 degree c inversion base near
3400 feet. This was a deeper...stronger inversion than yesterday
morning and given the thickness of the cloud layer...some areas can
expect similar...or even later clearing than yesterday. Surface
pressure gradients were running 2-5 mbs onshore to the deserts. Wind
gusts over 25 miles per hour were confined to desert areas below the wind-
The Broad Cut-off low dominating our weather was centered over
central California this morning. The low will drift NE into Nevada today...and
be absorbed into the westerlies on Monday. High pressure will build in
aloft from the south in the wake of the low...and peak over the
region on Wednesday. This transition will progressively lower the marine
layer for less extensive low clouds...but may result in more areas
of fog over coastal and western valley areas. Models show the
surface flow remaining onshore through this event...so some marine
influence will remain west of the mountains...helping the
temperatures to remain below values observed last week.
The global models are showing better agreement of late handling the
deepening trough across the eastpac this week. The trough will
deepen southeastward into the state by next weekend...bringing rain
to northern areas and cool...breezy conditions across the south.
There are still timing differences...but the pattern looks similar
on the various overnight model runs. This is half of a highly
amplified pattern across north.A. That includes a massive ridge across
the eastern half of the country. Given the strength of this blocking
ridge...it seems likely that our developing trough will slow or may
even cut-off over the region bringing an extended period of cool
weather into early October. The European model (ecmwf) ensemble mean is favored
here...locking in the trough across the west for some time.
211530z...coasts/valleys...widespread low clouds with bases around
2500 feet mean sea level and tops between 3000 and 3500 feet mean sea level cover most of the
area west of the mountains this morning. Local visible 3-5sm where clouds and
terrain intersect. Expect clearing between 17z and 19z. Low clouds
will return this evening with bases 1700-2200 feet mean sea level...moving into
the coastal airports after 03z and spreading about 25 Michigan inland
overnight. Likely reaching kont around 12z Monday.
Mountains/deserts...mostly clear with unrestricted visibility
830 am...no hazardous marine weather is expected through Thursday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.