Scientific Forecaster Discussion
fxus66 ksgx 062205
Area forecast discussion
National Weather Service San Diego California
205 PM PST Fri Dec 6 2019
a moist, southwest flow aloft will bring increasing clouds, with light
rain likely by evening. The clouds will persist through the
weekend, along with a chance for periods of light rain showers as
a weak storm system drops south across the state. It will move
east on Monday, with clearing skies and a warming trend for next
week. Further warming is on tap for next weekend as dry weather
persists. At the beaches, a large west swell bring high surf this
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Quick update to increase probability of precipitation through this evening. Doppler radar
shows a shield of rain entering Orange County extending south off
the San Diego County coast. This area is moving northeast at
about 35 mph. The radar bark is worse than the bite. Aircraft
sounding data shows a dry layer in the lower levels, so some of
the rain falling is evaporating. Upstream gauges over San Clemente
Island show Max rain over the past hour of 0.07". So this will be
a light rain but most coast and valley locales do look to get wet
late this afternoon through this evening. As such, increased probability of precipitation
substantially to account for this expectation. Rainfall of
trace-0.10 inches is expected through this evening west of the
mountains and along the coastal mountain slopes.
..previous discussion (issued at 1223 PM PST Fri Dec 6 2019)...
Satellite imagery at midday showed a thicker blanket of high clouds
spreading NE across the area. In addition, the radar indicated some
precipitation moving NE over the coastal waters. Some of this could
make it into Orange and San Bernardino diego counties by late
afternoon. The sfc pressure gradients from the deserts were still
weak to moderate offshore, supporting NE winds below the passes with
local gusts 25-35 miles per hour. Still, the sea breeze was evident into the
western valley areas.
A storm system centered 500 miles west of Cape Mendocino today, will
drift east through Saturday, and then drop south through Monday as a
strong ridge builds off the coast. Weak disturbances off the Pacific
ahead of it will gather up some Pacific moisture, sparking some
occasional light precip that will favor the coastal slopes. Upslope
is generally weak though, so no heavy amounts are likely with no
good atmospheric lift to squeeze it out. Snow levels will be quite
high initially, above 8k feet through Saturday, then fall to around 7k
feet by late Sunday.
The final trough axis passes through socal on Monday morning, so
some light, scattered showers may continue into early Monday for San
Diego County especially. Overall precip amounts of 1/4-1/2 inch are
expected west of the mts, and 0.5 to 1.5 inches on the coastal
slopes and higher terrain. For the deserts, less than one-quarter
inch total. Several inches of snow are possible in the San
Bernardino mts by Mon morning above 7500 feet.
A highly amplified ridge develops early next week along the West
Coast and keeps socal protected from activity in the westerlies
through next week. Even though the ridge flattens, it strengthens
further next weekend along 30n latitude. This will likley bring well
above average temps to socal by next weekend, along with continued
fair and dry weather.
062020z...coasts/valleys...sct-bkn high clouds at or above 20000 ft mean sea level and
unrestricted vis this afternoon. Cigs 2000-2500 ft mean sea level and vis 2-4
sm in areas of rain after 01z Sat.
Mountains...sct-bkn high clouds at or above 20000 feet mean sea level with unrestricted
vis through this afternoon. Low clouds will obscure terrain above
3000 ft msl, with vis 1-3 sm at times after 01z Sat with -ra/-sn.
Deserts...mostly clear skies through Fri. Chance of -ra Sat. Cigs
around 5000 ft mean sea level and vis 3-5sm possible in rain.
scattered rain showers this afternoon through Sunday. Combined seas
of 6 to 8 ft are expected Saturday afternoon through Sunday evening.
a high surf advisory has been issued as long-period northwest swells
of 14 to 18 seconds arrive at the coasts of Southern California. The
swells will start to build on Saturday, peaking Sunday morning, and
subsiding by Monday morning. Surf of 6-8 ft is expected in San Diego
County and 4-7 ft surf is expected on beaches prone to west-northwest swells in
California...high surf advisory from 4 am Saturday to 4 am PST Monday for
Orange County coastal areas-San Diego County coastal areas.