Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
825 PM PDT sun Mar 16 2014
high pressure will break down later tonight and on Monday...as a
trough of low pressure moves inland across the Pacific northwest.
As a result...significantly cooler conditions will develop over
Southern California for the first part of the work week. Onshore
flow will return as well...with gusty winds possible in the
mountains and deserts. The marine layer will also return...becoming
more widespread each night...with even some drizzle possible by
Tuesday morning. Although the flow may briefly turn offshore on
Tuesday and Wednesday...weak onshore flow will prevail through the
remainder of the week and weekend...with temperatures remaining near
or slightly above average.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Water vapor imagery shows high pressure over California this
evening...starting to flatten a bit in response to a trough
approaching the Pacific northwest. As this trough moves inland
later tonight and on Monday...the ridge will flatten and shift
westward...allowing cooler conditions to develop once again.
In the meantime though...the skies are clear...with relatively weak
surface gradients over the Southland. Temperatures for most
locations are running several degrees warmer than this time last
night...following the record breaking heat we had today. In
fact...four locations broke their previous records...Lake
Elsinore...Escondido...alpine...and El Cajon. As quickly as things
heated up around here...they will cool down starting tomorrow. The
local WRF shows a patchy marine layer even trying to reform late
tonight and for Monday morning. At this point in time...think that
if fog does form along the immediate coast...it will likely be
patchy in nature...but possibly dense in places by the morning
commute. Otherwise...expect temperatures to be 5 to 15 degrees
cooler than today...as 850 mb temperatures fall 3 to 4 degrees and
the onshore flow returns.
This cooling trend will continue into Tuesday...as the trough digs
over the Great Basin. The marine layer will likely rapid redevelop
and deepen on Monday night and Tuesday morning...in response to
this. The models are also showing an eddy developing over the
bight...with nearly 2500 feet of deepening possible. For this
reason...have added some drizzle to the forecast for areas west of
the mountains during this time period. Otherwise...expect dry and
slightly cooler conditions to continue on Tuesday...with some
locally gusty west winds possible in the mountains and deserts.
That being said...the models are now showing a brief period of
offshore winds developing on Tuesday and into Wednesday...with
temperatures moderating a bit by Wednesday. The marine layer will
also become shallower and less extensive. However...another trough
will then develop along the West Coast...with weak onshore flow and
a deeper marine layer possible through the remainder of the work
week and the weekend. Therefore...expect only minor fluctuations
possible in temperatures...with most places remaining near or
slightly above normal for the period.
170320z...coasts/valleys...clear with unrestricted visible through late
tonight. Patchy stratus with bases at or below 500 feet mean sea level and visible 3 sm or
less in br/fog possible over the coastal waters between 17/11-16z.
Low confidence in stratus/fog reaching the coastal airports by
morning...but if it does visibility may be reduced to 1sm or less.
Otherwise a few clouds at or above fl200 and unrestricted visibility through Monday
afternoon. Stratus with bases 800-1200 feet mean sea level moving into the
coastal airports 18/01-04z. Bases lifting to 1500-2000 feet mean sea level Monday
night with tops to 2500 feet mean sea level. Areas of visibility 2-5sm possible as
stratus moves inland.
Mountains/deserts...a few clouds at or above fl200 and unrestricted visibility
through Monday evening. West winds with surface gusts 30-45 knots Monday
afternoon and evening. Low level wind shear...rotors...and moderate-strong uddfs possible
over and east of the mountains with these winds.
a long-period northwest swell arriving this evening will peak Monday around
7-8 feet with a period of 17 seconds. This will result in elevated
surf at beaches south of del Mar in San Diego County...and around
Huntington Beach in Orange County. Local sets of 7-8 feet at the
favored west facing beaches Monday and Tuesday. Large tidal swings and
elevated surf will create strong rip currents as well. Surf and
swell will subside Wed/Thu. See cfwsgx for details on the beach
hazards statement in effect through Tuesday evening.
A 6-8 feet short-period northwest swell will move into the outer coastal
waters Monday afternoon and build into portions of the inner waters Monday
night due to a 25-30 knots wind fetch from Point Conception to just
west of San Clemente Island. Combined seas of around ten feet are
likely late Monday/Monday night along with northwest winds of 15-20
knots...resulting in rough seas and hazardous conditions for small
craft. A Small Craft Advisory has been issued for Monday afternoon
through early Tuesday morning. See laxmwwsgx for details.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...beach hazards statement through Tuesday evening for the beaches
in the Orange County coastal areas...San Diego County
Pz...Small Craft Advisory for hazardous seas from 3 PM Monday to 9 am
PDT Tuesday for the coastal waters from San Mateo Point to
the Mexican border and out 30 nm...waters from San Mateo
Point to the Mexican border extending 30 to 60 nm out
including San Clemente Island.