Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
910 PM PDT Tuesday Sep 2 2014
fair weather will prevail through early next week. A low pressure
system to the north will bring some cooling Wednesday with little
temperature change Thursday. Low clouds will extend into most
valleys during the nights through Thursday due to a deeper marine
layer...and there will be locally gusty winds in the mountains and
deserts...mainly in the late afternoons and evenings. High pressure
from the southeast will build a little Friday through the weekend to
bring slight warming and fewer low clouds...then some cooling will
return early next week as the high weakens. Monsoonal moisture will
approach early next week...but the moisture appears to be
insufficient for thunderstorms.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The 00z sounding from Miramar showed the marine inversion base was
around 1800 feet mean sea level and the top at about 3600 feet mean sea level with a Delta T
value of 6 degrees c...very similar to yesterday at this time.
Stratus decks have already infiltrated much of the San Diego and
part of the Orange County coasts and the push will continue
through the night. The marine layer will remain climatologically
deep the next few days and may even strengthen a bit as heights
fall a bit due to the upper level trough to our north.
Temperatures around the area will continue to be a few degrees
below normal for the next few days.
03330z...coast/valleys...low clouds moving into coastal areas
04-08z...and reaching 22-32 miles inland by 12z. Overnight into
Wednesday morning...bases will be 1500-1700 feet mean sea level with tops
2000-2300 feet mean sea level. Visible restrictions will occur where low clouds
intersect higher terrain...and over portions of the inland Empire.
Low clouds will retreat to the coast between 15z and 18z Wednesday.
After 18z...mostly clear skies with few to scattered low clouds over the
coastal waters through 02z Wednesday. Low clouds returning to the
coast 03-07z Thursday.
Mountains/deserts...unrestricted visible with clear skies through
830 PM...no hazardous marine weather expected through Saturday
Previous discussion (issued at 200 PM today)...
a low pressure trough will gradually deepen and expand over Oregon
and northern California Wednesday through Thursday while the high
pressure ridge will extend from Sonora east through the Southern
Plains/Gulf states. Height falls will help maintain a relatively
deep marine layer...though the models show the inversion weakening.
Temperatures aloft will continue to lower and bring temperatures averaging
about 5 degree f below normal Wed/Thu...more in some of the valleys and
western foothills. Some locally windy conditions will occur as
onshore pressure gradients local WRF shows some local sustained
surface winds of 25 knots in the windiest desert/desert slope
locations for Wednesday and Thursday late afternoons/evenings...so gusts could
reach 45 miles per hour. This will only in places that normally get winds like
this such as through/east of San Gorgonio Pass...so we do not plan
on a Wind Advisory right now.
High pressure aloft over the southern US will build west a little
bit Friday and have an axis from northern Baja California California east to
Texas over the weekend. The trough will continue over northern
California...but height rises here will mean the high will dominate
and result in warming and a more shallow marine layer for less
extensive nocturnal stratus. The upper high shifts south a bit early
next week as long-wave troughing forms over the intermountain west
and northern plains...so some cooling could occur here then...mainly
inland. A possible tropical system to our southwest will likely not
bring much moisture here...but some moisture from the southeast will
move up around the west side of the upper high. However...the
westerlies will prevail just to our north...so most likely we will
just have enough moisture for cumulus but not enough for
thunderstorms. Thus...our forecast is for dry weather continuing
through early next week.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.