Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
151 PM PST Thursday Nov 26 2015
a cold and nearly stationary low pressure system over the Great
Basin will bring cool weather through Friday...partly to mostly
cloudy skies and periods of scattered to isolated mainly light
showers over and west of the mountains. Light snow accumulations
possible in the mountains above 4500 foot elevation. Drier and
gradually warmer Saturday through most of next week due to weak
offshore flow and higher pressure aloft. Overnight lows may get
below freezing in portions of the valleys and deserts this
weekend...resulting in possible frost or freeze conditions.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Radar imagery this afternoon shows that the shower activity from
this morning has quieted down. Additional rainfall amounts this
morning were fairly light...mainly a trace to a few hundredths of an
inch. Taking a look at temperatures...looks like the snow level has
risen to about 5500-6000 feet this afternoon...with only some
flurries/brief snow showers reported above that level. As the upper
level trough continues to hang out over the Great Basin area...hi-
res models continue to bring periods of scattered to isolated light
showers to the forecast area over and west of the mountains through
Friday night. There does look to be an increase in shower activity
tonight into tomorrow...mainly for San Diego County...as a potent
vorticity maximum rotates around the trough into Southern California. Some of
these showers could bring moderate rainfall. Additional
precipitation amounts through tomorrow will be mostly light and
highly variable...with San Diego County receiving possibly an
additional 0.25 to 0.50 inches...while the rest of the forecast area
west of the mountains receives mainly a few hundredths to a tenth of
an inch...and locally 0.25 inches. Snow levels look to be at around
4500-5000 feet through that period...although they may drop down to
4000 feet during the overnight hours. A trace to a couple inches of
snow is possible above 4500 feet. Continue to not see much
instability...except over the warmer than normal waters...so
thunderstorms over land areas appears unlikely. Meanwhile...day-time
highs today and Friday will continue to be 10-20 degrees below
normal...except near the coast where temperatures will be more like
3-7 degrees below normal. Expect partly to mostly cloudy skies to
continue with the lingering moisture and cold air over the region.
Friday night through Monday...weak offshore flow and drying will
occur with surface high pressure building over the Great Basin and
the trough moving off to the east with a weak ridge moving in aloft.
This will result in very gradual warming and a lack of night and
morning marine layer clouds/fog. There may be enough lingering cold
dry air and light winds to create significant enough radiational
cooling to bring areas of frost and freeze over the inland valleys
and deserts overnight Friday...Saturday and possibly Sunday. A
freeze watch is in effect for the high deserts and central/eastern
inland Empire for overnight Friday. Some areas in the inland Empire
could have some patchy frost...but confidence is low that it will
cover a large area due to the lingering showers and moisture in the
Mostly fair weather will likely continue Tuesday through the end of
the work-week...with zonal flow aloft...weak offshore surface
flow...and continued slow warming. However...there are indications
that a couple week troughs could move through the region...which
would result in less warming than expected.
262030z...sct/bkn low clouds...with bases from 4000 to 5500 feet mean sea level
and tops near 8000 feet mean sea level...will continue across portions of the
region through Friday afternoon. Coastal mountain slopes and ridges
will be obscured in clouds/fog at times. -Shra will be possible over
portions of San Diego County through Friday...mainly this evening
and again late Friday morning. Forecaster confidence is mod-high.
1230 PM...isolated showers are possible through Friday. No hazardous
marine conditions are expected Saturday through Monday.
1230 PM...astronomical high tides near 7.3 feet at 912 am Friday
morning will create a threat of minor coastal flooding. A coastal
Flood Advisory remains in effect for coastal Orange and San Diego
counties through noon Friday. Strong rip currents will likely occur
from slightly elevated surf today...and during the transition from
high to low tide Friday morning. Conditions will improve this
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...freeze watch from late Friday night through Saturday morning for
apple and Lucerne valleys-San Bernardino and Riverside
County valleys-the inland Empire.
Coastal Flood Advisory until noon PST Friday for Orange County
coastal areas-San Diego County coastal areas.