Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
142 PM PDT Wednesday Mar 12 2014
mostly sunny and dry with locally gusty northeast winds in and below
passes and canyons through this afternoon. The marine layer and a
coastal eddy will keep San Diego County coastal areas cooler with
areas of night and morning low clouds and fog into Saturday. Dry and
much warmer for Friday through the weekend...with locally gusty
winds near the coastal foothills at times. A cooling trend is
expected for next Monday through Wednesday.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The marine layer low clouds and fog had been pushed west several
miles off the coast...but are now moving back towards the South
San Diego County coast. Surface pressure gradients are offshore to the
north and onshore to the east with -7.2 mb san-tph and +2.7 mb
san-czz...but gradients are now trending onshore. Gusty offshore
winds continue with Fremont Canyon reporting gusts to 49 miles per hour last
hour and Highland Springs reporting gusts to 40 miles per hour.
Closed upper level low pressure centered over central California
will move to the southwest over Southern California by
Thursday...then move east over Arizona and New Mexico on Friday.
Surface high pressure over the Great Basin and the western rockies
will continue to bring gusty offshore winds to northern areas
through this afternoon...weakening and continuing into Thursday.
The upper level low pressure center moving southward into the
region tonight will enhance the low level coastal eddy
circulation with coastal low clouds and fog spreading inland...and
the marine layer deepening late tonight into early Thursday
morning. Based on current high resolution models...there could be
a quick transition to onshore flow across portions of socal tonight...with
the marine layer reaching the inland valleys Thursday and Friday
For Friday through the weekend...an upper level high pressure ridge
will build in from the west over California...and combined with weak
surface high pressure over the Great Basin will bring significant
warming and continued dry weather with locally gusty northeast winds
near the coastal foothills at times. The high pressure aloft and the
offshore flow will reduce the marine layer. However...the latest
high resolution models maintain some patchy low clouds near the
coastal strip into Saturday morning. Daytime temperatures could
reach the middle to upper 80s across the inland valleys...and the 70s
to low 80s near the coast on Sat and sun.
Onshore flow will return for next week with a cooling trend and
increasing marine layer.
122020z...mostly clear skies and p6sm will prevail for the rest of
the afternoon. Low clouds expected to return to coastal airports
after 03z tonight with bases around 1500 feet above sea level and a thickening
cloud layer as a coastal eddy develops...pushing 15 to 20 miles
inland overnight. Stratus will erode to the coast between 16-18z
Thursday...however...some low clouds may remain along the beaches
into the afternoon if the eddy persists. Areas of northeast winds
will continue to weaken this afternoon.
a red flag warning for strong northeast winds and low humidity
remains in effect for this afternoon. In addition...reports
indicate that in many areas fuels have not sufficiently responded
to the recent rains to reduce the wildfire threat.
Fog and low clouds cover portions of the Orange County coastal
areas...the San Diego County coastal areas and the San Diego County
valleys this morning. Elsewhere...humidities are mostly below 20
percent with gusty offshore winds. The offshore winds will peak
later this morning...then decrease during the afternoon. Strongest
wind gusts exceeding 55 miles per hour have occurred through and below passes
and canyons of the San Bernardino and Santa Ana Mountains. We may
transition quickly to onshore flow over much of the region by late
tonight and good humidity recoveries are likely at low elevations
west of the mountains...with the possible exception of the inland Empire.
Continued dry and breezy at higher elevations inland on
Thursday...but conditions are not expected to be critical due to
lighter winds and some humidity recovery. Very warm and dry...with
weak offshore flow for the weekend.
California...red flag warning until 6 PM PDT this evening for the Coachella
Valley-including the Palm Springs South Coast desert
district...Orange County coastal areas...Riverside County
mountains-including the San Jacinto Ranger district of the
San Bernardino National Forest...San Bernardino and
Riverside County valleys-the inland Empire...San Bernardino
County mountains-including the mountain top and front
country Ranger districts of the San Bernardino National
Forest...Santa Ana Mountains-including the Trabuco Ranger
district of the Cleveland National Forest.
Wind Advisory until 6 PM PDT this evening for the Orange County
coastal areas...San Bernardino County mountains...San
Bernardino and Riverside County valleys-the inland Empire...
Santa Ana Mountains and foothills.