Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
908 PM PST Wednesday Dec 24 2014
cooler conditions will develop for Christmas day...as a trough of
low pressure moves inland across northern California and into the
Great Basin. Gusty west winds will continue overnight across the
mountains and deserts. As this system shifts east...periods of
gusty northeast winds will return to the coastal slopes of the
mountains and adjacent coastal foothill areas through Saturday.
Although some minor warming may occur this Holiday weekend...cool
conditions will continue...with even cooler conditions possible
for the first part of next week.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Onshore pressure gradients have spiked over the last 6 hours with
the San Diego to gaggett gradient...for example...up to 5.2 mb
last hour. Wind gusts have been measured recently up to 60 miles per hour in
the favored gap wind areas of the San Bernardino...Riverside and
San Diego County mountains. Winds will likely surface into the
desert slopes after midnight and continue until about daybreak
Christmas morning. Gusts up to 75 miles per hour will be possible in the
favored locations. Meanwhile the onshore push has started to
generate marine stratus decks in a few spots including lax and
sna as well as dense fog at the Avalon Airport on Catalina Island.
Onshore flow quickly slacks Thursday morning and as the fast
moving trough kicks off to the east...moderate offshore flow will
develop once again and generate some strong wind gusts once again
from the northeast.
Rain showers are also coincident with the trough...now over the
southern San Joaquin Valley and approaching the Tehachapi
Mountains just north of the la basin. Rain showers and snow
showers above 6000 feet will be possible after midnight and
diminishing around daybreak. Some drizzle also possible towards
daybreak near the coast due to rapid strengthening of the marine
Previous extended discussion...
although a minor warming trend will develop for the weekend under
weak ridging...cool conditions will continue to prevail. The 12z
models are continuing to hint at a potentially impressive dry back
door cold front spreading into Southern California early next
week...sometime between Monday and Wednesday. There are still a
few timing differences...with the GFS timing a little faster with
the initial surge of cold air...but both models are showing a
surge of very cold air for Tuesday and Wednesday. Given the
trajectory of this system...believe that dry conditions will
prevail. However...very gusty north to northeast winds will
probably be in store for these days as well.
250445z...coast/valleys...areas of stratus will continue to develop
this evening with bases 1000-2000 feet mean sea level...rising to 2000-3000 feet
mean sea level after 08z...with tops to 5000 feet mean sea level late tonight.
Isolated/scattered light showers will occur mainly 08z-15z...with
only local visible reductions below 5 Michigan then. Higher terrain will be
locally obscured. Mostly scattered conditions will occur after 16z
Thursday...with areas of surface gusts from the NE 30-40 knots developing
by 18z in the Santa Ana moutains and below the Cajon
Pass...including vicinity kont...ksbd...kral...kcno...with low level wind shear and
strong up/downdrafts. The winds will continue Thursday night.
Deserts/mountains...SW-W winds with surface gusts 40-50 knots will
occur through 15z Thursday over the mountain crests...desert slopes and
adjacent desert foothills...with associated low level wind shear and strong
up/downdrafts. Areas of terrain on the coastal slopes mainly below
5000 feet mean sea level will be obscured 08z-16z.
845 PM...a trough of low pressure moving by to the northeast tonight
into early Thursday will bring gusty west-northwest winds to the coastal
waters. Wind gusts of 25 knots...locally higher...are likely over the
coastal waters late tonight through midday Thursday. Combined seas of 10-12
feet are also possible for a short time early Thursday over the outer
coastal waters due to the combination of the elevated west swell and
the wind waves...so seas will be choppy and confused. Winds will
weaken gradually Thursday afternoon/evening. A Small Craft Advisory is in
effect for the inner and outer coastal waters this evening through
845 PM...a long-period west-northwest will continue elevated
surf of 3-5 feet...with occasional sets to 7 feet...and strong rip
currents at the San Diego and Orange County beaches through Friday.
Swell and surf will subside over the weekend.
California...Small Craft Advisory until 2 PM PST Thursday for the San Diego
County coastal areas.
Wind Advisory until 6 am PST Thursday for the Coachella Valley...
Riverside County mountains...San Diego County deserts...San
Diego County mountains.
Wind Advisory until 3 am PST Thursday for the apple and Lucerne
valleys...San Bernardino County mountains.
Pz...Small Craft Advisory until 2 PM PST Thursday for the coastal
waters from San Mateo Point to the Mexican border and out
30 nm...waters from San Mateo Point to the Mexican border
extending 30 to 60 nm out including San Clemente Island.
previous extended discussion...Palmer