Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
730 PM PST Sat Nov 28 2015
Synopsis... we will be in a quiet weather pattern through Wednesday
with weak offshore flow bringing mild days and cold nights. Low
temperatures will fall near or below freezing in the inland valleys
and lower deserts where frost advisories or freeze warnings will be
in effect. On Friday a weak Pacific trough will bring clouds and
perhaps a few light showers.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
A tranquil weather pattern is forthcoming next week with mild days
and cold night. But first there are two vorticity maxes we are watching
that will drift across Southern California tonight and
Sunday...neither of which is very strong or has much moisture.
The first wave west of pt Conception this evening will race
southeast across northern Baja California early Sunday morning. The models show
a small increase in precipitable water to 0.70" late tonight which
will bring some clouds and an outside chance at a few light showers.
But most areas will not see any rain. The airmass is just too dry.
However...this small increase in midlevel moisture may keep
temperatures a couple degrees higher than last night.
A second weaker and drier shortwave with origins over the Great
Basin may generate a few light showers over the San Bernardino
Mountains Sunday as it moves southeast down the California interior.
The main weather story the next several days will be the cold
nights. Mountain lows will fall into the teens and 20s...and a few
areas in the San Bernardino Mountains may reach the single digits.
In The Lowlands the concerns involve freezing temperatures. Coldest
nights will be Sunday through Tuesday when clear skies...light winds
and a very dry airmass will result in efficient radiational cooling
after sunset in wind sheltered areas. Have updated the forecast to
lower min temperatures in most areas Sunday night through Tuesday
night. Frost advisories or freeze warnings may be needed for some or
all of those nights.
While the nights will be cold...the days will be mild. There will be
a few degrees of warming each day through Wednesday as heights and
On Thursday heights begin to fall and onshore flow will return ahead
of a weak upper level trough approaching from the west. Most of the
energy with this system will bypass US to the north...but a slight
southerly jog of the storm track could support a few showers this
far south on Friday. A moderate amplitude ridge will build in behind
the exiting trough for sunny...warm weather next weekend.
Aviation... 290315z...VFR with unrestricted visible through
Sunday...with few-scattered clouds in the 5000-15000 feet mean sea level layer becoming
broken after 29/1000 UTC. Local NE winds 10-20 knots gusting to 30 knots
through passes/canyons and along the coastal foothills this evening
will decrease through 29/1200 UTC.
Marine... 7 PM PST...no hazardous marine conditions are expected
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...freeze watch from late Sunday night through Monday morning for
San Bernardino and Riverside County valleys-the inland
Empire-San Diego County deserts-San Diego County valleys.
Freeze warning from 1 am to 8 am PST Sunday for apple and
Lucerne valleys-San Bernardino and Riverside County valleys-
the inland Empire-San Diego County deserts-San Diego County