Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
754 PM PST Friday Dec 19 2014
a weak upper-level trough will drift across Southern California
tonight...increasing clouds...and bringing some isolated sprinkles
or mountain snow flurries. High pressure will then rebuild along
the West Coast...and offshore flow will develop for dry and warmer
days through early next week. The offshore flow may get gusty below
the canyons and passes at times before winds turn back onshore
Christmas day. Cooler...and likely remaining dry on Christmas and
through the Holiday weekend.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Layers of high clouds were spreading southeast across the region
this evening. At 8 PM PST...winds were mostly light and radars in
the area indicated no precipitation. The 00z Miramar sounding
indicated most of the meager moisture available was above 20k feet.
A weak shortwave trough will move from northwest to southeast across socal
overnight. Even though high clouds are abundant...it is unlikely
much if any precipitation will survive the trip through the dry
layer. A few sprinkles are possible...but measurable precipitation
is unlikely. Onshore flow at the surface will maintain some marine
influence and clouds west of the mountains through the weekend...
but the airmass will gradually warm and dry.
A strong ridge of high pressure will reemerge over the eastpac...
reaching 590+ dm by sun...and not weakening until middle next week.
This will result in warm days and offshore flow across socal Monday/
Tuesday. Surface flow will weaken on Wednesday as a short wave flattens the
ridge...and become onshore into Christmas day as a broad trough
develops across the Continental U.S....and the high offshore weakens.
Warmer Sunday...with further warming Monday-Wednesday and temperatures some 7
to 15 degrees f above average. Closer to normal for Christmas day
and through the Holiday weekend. Some return of marine layer clouds
is possible Christmas evening into Christmas day...otherwise skies will
The 12z operational European model (ecmwf) solution does dig a strong shortwave south
along the coast on Christmas day that produces some light
precipitation here. However...the weaker and dry GFS solution is
preferred and followed into the extended period of the forecast.
200400z...variable high clouds will continue with scattered to
locally broken low clouds overnight. When/where they develop...low
cloud bases will be around 2500-3000 feet mean sea level most likely between
06-12z. Scattered clouds Saturday...then ceilings of around 2500 feet
mean sea level appear more likely after 02z Saturday evening.
800 PM...no hazardous marine weather is expected through Wednesday.
800 PM...a large swell with a long period will build Saturday and
bring higher surf and stronger rip currents late Saturday through
early Sunday. In addition...morning high tides around 7 feet could
contribute to minor coastal flooding and/or tidal overflow through
Tuesday. See the beach hazard statement for details...laxcfwsgx.
Skywarn activation will not be needed through Saturday.
California...beach hazards statement from late tonight through Tuesday
morning for the Orange County coastal areas...San Diego
County coastal areas.