Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
900 am PDT Friday Oct 31 2014
a trough of low pressure deepening along the West Coast today will
bring cooler weather and a rapidly deepening marine layer. Rain and
higher mountain snow are likely tonight into Saturday morning with a
few showers possible through Sunday morning. Warmer days next week
as high pressure and offshore flow develop.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The marine layer has deepened considerably with some clouds reaching
up mountain slopes to 5000 feet and nearly all of the coastal basin
is shrouded. Some clearing is expected today...but not a whole lot.
A low pressure trough...our first of the season...is deepening off
the West Coast today and is already spreading some rain through
nocal. This system will continue to dig southward tonight. Socal is
on the southern edge of this system...but a legitimate cold front is
headed our way. Moisture becomes deep enough and energy sufficient
for a broad band of precipitation moving through our region
happening mostly between midnight and 10 am tonight and Saturday
morning. There may be some light showers before midnight that could
make some streets wet for Holiday parties...but trick or treaters
finishing early enough should avoid most showers. Snow will fall in
the higher elevations and levels will drop to about 6000 feet after
the passage of the cold front early Saturday. Several inches are
possible above 7000 feet...but less than 3 inches below. Lingering
showers are possible through Saturday mainly for the mountains and
far southern San Diego County. Winds will start out gusty through
mountain ridges and passes tonight...but become quite strong and
more widespread as the cold front arrives early Saturday. All
mountains and deserts should prepare for some strong winds Saturday
before decreasing late afternoon. The low pressure trough has a
second wave; it is much weaker but rotates through our region early
Sunday morning. This could coax a few more showers to develop
Saturday night and Sunday morning mainly in mountains and southern
San Diego County...some a result of island bands. Temperatures over the
weekend will be below average...with highs mostly in the 60s at
lower elevations. On Monday and Tuesday the second wave moves off
and a high pressure ridge noses into the West Coast. Models differ
on how strong of a ridge it will be...but fair...dry and much warmer
weather is coming. Some offshore flow sets up at the same time to
add to the warming/drying trend. On Wednesday there could be some
decent offshore winds in the usual spots. Temperatures will head into the
80s even near the coast by Wednesday.
311530z...multiple broken cloud layers with bases 2000-4000 feet mean sea level west
of the mountains through the morning. Clouds becoming scattered-broken with
bases 3000-4000 feet mean sea level after 16-18z. Bases lowering back to around
2000 feet mean sea level after 01/00z. A cold front will bring scattered light
showers along and west of the mountains beginning around
01/01-03z...becoming heavier and more widespread after midnight with
lowering ceilings. Light showers possible over the high deserts after
01/10z...with little if any precipitation in the low deserts. Local
MVFR/IFR ceilings and visible possible in heavier showers. Coastal slopes of
the mountains will be obscured in clouds and precipitation through Sat
SW to west winds 20-30 knots gusting to 40-50 knots over mountain ridges and
along desert slopes/adjacent desert foothills will create moderate-strong
uddfs...low level wind shear and rotors east and NE of the mountains after 21z. Visible
locally reduced to 5sm or less in bldu/hz.
830 am...no hazardous marine weather is expected today. A cold front
moving over the coastal waters will bring west to northwest winds
gusting to 25-30 knots and steep waves Saturday. A Small Craft Advisory
will be in effect from early Saturday morning through late Saturday
night...see laxmwwsgx for details. Conditions will improve during
the day Sunday.
Skywarn activation is not requested for today. Skywarn may be
requested for late tonight and Saturday morning...primarily for
urbanized and burn scar flooding concerns and snow in the higher
elevations. Weather spotters are encouraged to report significant
California...Wind Advisory from 8 PM this evening to 5 PM PDT Saturday for
the apple and Lucerne valleys...Coachella Valley...
Riverside County mountains...San Bernardino County
mountains...San Diego County deserts...San Diego County
Winter Weather Advisory from 11 PM this evening to 2 PM PDT
Saturday above 6500 feet for the Riverside County
mountains...San Bernardino County mountains.
Flash Flood Watch from this evening through Saturday morning for
the Santa Ana Mountains and foothills.
Pz...Small Craft Advisory for winds from 5 am PDT Saturday to 4 am
PST Sunday 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.