Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
1110 PM PST Thursday Nov 26 2015
Snow showers developing across the San Diego and Riverside County
mountains...will continue off and on overnight. Additional lobes of
energy around the upper low will contribute to additional snow
showers through at least Friday early afternoon with snow level
fluctuating around 4000 feet. Have issued a Winter Weather Advisory
for those areas around 4000 feet and higher. Travel may be hampered
on the I-8 corridor and sunrise Highway.
a cold low pressure system centered over the Great Basin...will
keep the weather cool through the Holiday weekend. Periods of
showers are likely through Friday night along and west of the
mountains as weak disturbances rotate around the area of low
pressure to the north. Highly variable snow accumulations of a
trace to locally several inches are possible in the mountains above
4500 feet. The nights will be quite cold this weekend with below
freezing temperatures likely in some valleys and desert areas. Dry
and warmer next week as the low drifts east and weak offshore flow
once again prevails.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Probability of precipitation were raised late this afternoon with a trace to locally three
inches of snow expected in the mts above 4500 feet by late Friday. Areas
near and just east of Crestline have received several inches of snow
this evening. Some snow has made it into Lucerne Valley as well...but
little accumulation is expected there.
Radar showed scattered showers continuing to develop over the
coastal waters and move inland this evening with light accumulations
of rain...and snow at higher elevations. Snow was reported down to
4800 feet on Palomar Mountain. A persistent area of weak to moderate
echoes was responsible for the accumulating snow this evening near
Satellite imagery showed a broad sweep of clouds arcing south and
east well off the central California coast into the California bight. The 00z Miramar
sounding had a very steep lase rate once again below 6500 feet...but
there was little moisture to work with given a precipitable water of 0.37 inch. West
winds had increased to around 100 kts at 25k feet...but were uniform
around 15 knots from the west-northwest below 6k feet. Surface pressure gradients
were offshore now from Nevada at 4 mbs but onshore at 2-3 mbs to the
lower deserts. Unlike the past few days...strongest wind gusts were
only 20-25 miles per hour at 8 PM PST.
Based on water vapor imagery this evening...it appears one
disturbance is moving across socal now...with another on the way
late tonight into Friday morning. And given the low-level wind
profile...expect island banding to contribute to additional shower
development overnight. Despite the very low precipitable water...thermal support from
the warmer than average ocean surface...and jet dynamics associated
with these features has been sufficient to squeeze out showers...with
snow falling in the San Bernardino mts above 4500 feet. So expect this
activity to continue off and on with light rates of accumulation
through Friday. This will make for another cool...and somewhat damp day
in some areas. The hires models favor San Diego County to receive
most of the precipitation. Trace to two inches of snow could be widespread
by Friday afternoon in the mountains...with local amounts of 3 inches or
more on the higher peaks. The nights will be quite cold this weekend
with below freezing temperatures likely in some valleys and desert
From previous discussion...
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.
270500z...sct/bkn clouds...with bases 3500 to 5500 feet mean sea level and tops
to near 9000 feet mean sea level...will continue from the mountains west to the
coast through Friday afternoon. Scattered rain showers will locally
reduce surface visible to 3-5 Michigan...except above 4500' elevation...scattered
snow showers and mountain terrain obscurations will reduce surface visible to
less than 1 Michigan. Clouds will gradually decrease Friday evening.
930 PM...scattered showers will continue through Friday. No hazardous
marine conditions are expected Saturday through Tuesday.
930 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
during the transition from high to low tide Friday morning.
Conditions will improve this weekend.
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.
Winter Weather Advisory for San Diego and Riverside County mountains
through 4 PM Friday.