Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
345 am PST Thursday Dec 12 2013
mild today with scattered high clouds from low pressure aloft. The
upper low will move east tonight followed by slightly cooler weather
west of the mountains Friday as a trough moves in from the north.
Warmer Saturday and Sunday with gusty northeast winds in the
mountains and valleys. Warm and dry Monday and Tuesday with lighter
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The closed upper low over Ensenada this morning is sending high
clouds into Southern California. Doppler radar detected a few weak
<30 dbz echoes over San Bernardino County this morning drifting
northwest. The atmospheric profile has not changed much the past 24
hours with a deep moist layer from 750-350 mb...and a dry layer from
the surface to 750 mb. Like yesterday...any precipitation that reaches the
ground will be light...and most of the rain will evaporate before it
reaches the ground. Best chances for any light precipitation will be light
snow showers of flurries in the mountains this morning.
The low moves east over the lower Colorado River valley this
evening...then is ejected more quickly eastward into Arizona tonight
by a shortwave moving down the California interior. This shortwave
trough will bring a period of stronger onshore flow Friday with
areas of low clouds in the coastal zones Friday morning as a shallow
marine layer forms. The coastal and valley zones will be a little
cooler Friday...with little temperature change in the mountains and
On Friday evening the trough passes over socal. The flow aloft turns
quickly offshore Friday night/Saturday morning as a 1035 mb surface
high builds over Nevada. 850 mb winds shift NE and increase to
20-25kt. The 2km cansac WRF shows surface winds increasing to
30-40kt around 06z Saturday and continuing quite strong through
Saturday morning. At a minimum...this will be a Wind Advisory
event...and perhaps a High Wind Warning event with gusts of 60 miles per hour
in the wind prone areas of the Cajon Pass...the Orange County
mountains...the San Gorgonio Pass and the mountains of San Diego
Moderate to strong offshore winds will continue through Sunday
morning...then not quite as strong Monday and Tuesday as the Great
Basin surface high weakens.
Rising temperatures...this warm dry offshore event will push
temperatures well above average Sunday through Tuesday. The marine
layer will be pushed out the sea so the warming will reach all the
way to the coast. Maximum temperatures will climb into the 80s in some areas
west of the mountains. The warmest days will be Monday and Tuesday.
Cooling Wednesday through Friday as a cold trough digs south from
Canada. The 06z GFS is much deeper and colder with the trough over
the west than the 00z European model (ecmwf)...but neither model has demonstrated any
consistency in the long range so confidence is low.
121000z...some clouds at or above 10000 feet above sea level this morning...otherwise
mostly clear with unrestricted visible today and tonight.
Fire...gradual relative humidity recovery through Friday with offshore flow
weakening today...then turn onshore Friday. Moderate to strong
offshore winds will develop again Friday night/Saturday with gusts
of 50 miles per hour or more through and below the favored canyons and passes.
The warm...dry offshore flow will lower humidities into the single
digits and teens over the weekend elevating the wildfire danger.
Gusty winds continue into Sunday. Continued warm and dry Monday and
Tuesday with lighter offshore winds.
Skywarn activation is not requested. However...weather spotters are
encouraged to report significant weather conditions.