Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
923 PM PDT Monday Mar 10 2014
developing low pressure aloft will bring slightly cooler days and
some low clouds along the coast through Wednesday. Weak onshore flow
will turn offshore and become strong and gusty below passes and
canyons Tuesday night and Wednesday. Gradually warmer Thursday
through Sunday with periods of offshore flow as high pressure builds
back over the state. Quite warm next weekend with daytime high
temperatures well above normal and weak to moderate offshore flow.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Skies were mostly clear this evening across socal with just a few
high clouds. Surface pressure gradients were trending onshore and
winds were responding. Windier areas of the High Desert and
mountains had westerly winds of 15 to 25 miles per hour at 7 PM PDT. The 00z
Miramar sounding showed no marine layer and an about face of the
winds from east to west below 15k feet. Surface dewpoints have jumped
as well and were well into the 50s along the coast by 8 PM PDT. The
higher dewpoints and surface pressure gradient trends support some low
cloud and fog development tonight into Tuesday morning.
A shortwave trough is topping the West Coast ridge this evening and
will continue eastbound on Tuesday. However...another piece of energy
will dig back under the ridge and carve out an upper low over
central California/southern Nevada. As the upper ridge builds back to the north
of the upper low...surface pressure will build over the Great Basin
and force offshore flow through the passes and canyons of socal late
Tue/Wed. Models indicate cooling associated with the upper low will
intensify the thickness gradient across the transverse ranges and
augment the winds as they punch through the gaps and passes. The
stronger model solutions have wind gusts over 60 miles per hour through wind
prone areas like the Cajon Pass and the Santa Ana Mountain canyons. The
winds will be gradient driven without upper support until the upper
low moves east on Thursday. At that time surface gradients will weaken...but
upper support will increase to keep gusty wind in some areas.
Several runs of the nam12...including the new 00z run support high
wind conditions through and below the Cajon Pass and the Santa Ana
Mountains Wednesday morning. The NAM may be too aggressive in the digging and
movement of the upper low...not digging it west enough like the
other global model runs. Placement of the incipient upper low will
determine if any upper-level support will be available during the
peak surface gradient period. If further 00z guidance support the
stronger winds...the Wind Advisory may need to be upgraded to a high
wind watch for the northern areas late Tue/Wed.
Otherwise...fair and a bit cooler on Tuesday with onshore flow and a
possible eddy over the coastal waters. Any marine clouds that
develop overnight should burn off quickly. Fair on Wednesday...except for
possible low clouds along the San Diego County coast in the morning.
Despite the sinking and compressional warming expected...cold air
advection will counteract any big temperature jumps until the upper
low moves east and thickness recovers. Fair and dry with gradual
warming through next weekend under building high pressure aloft and
weak to moderate offshore flow at times. Daytime temperature will be
well above normal by the weekend into early next week.
a Fire Weather Watch has been issued for the zones north of San
Diego County for Wednesday due to expected strong northeast winds
and very low relative humidity. In addition...many areas report that fuels have not
sufficiently responded to the recent rains to reduce the wildfire
The winds will pick up Tuesday night...but relative humidity is not expected to fall
below the 15 percent threshold until Wednesday morning. The winds will
peak Wednesday morning through midday...then drop off rapidly late in the
afternoon. Strongest wind gusts over 50 miles per hour will occur through and
below passes and canyons in the San Bernardino and Santa Ana
Mountains. Continued dry and breezy on Thursday but conditions are
not expected to be critical due to lighter winds and some relative humidity
100420z...VFR conditions will prevail across the majority of the
Southland through the next 24 hours...with just a few high clouds
drifting across the region. However...low clouds are starting to
form along the San Diego County coast and border with Baja California. Knrs is
reporting scattered at 1000 feet...and these low clouds will likely
spread northward along the immediate coast tonight...as an eddy
spins up. At this time...think there is a pretty good chance that
the stratus will impact ksan between 07z and 12z...but may stay just
west of kcrq and ksna. The stratus should then pull back by
15z...with VFR conditions prevailing.
the elevated west to northwest swell that generated surf of 3 to 5
feet today will gradually decrease on Tuesday and Wednesday.
Another long period west to northwest swell is forecast to arrive on
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...Fire Weather Watch from Wednesday morning through Wednesday
afternoon 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 from 11 PM Tuesday to 6 PM PDT Wednesday for the
Coachella Valley...Orange County coastal areas...Riverside
County mountains...San Bernardino County mountains...San
Bernardino and Riverside County valleys-the inland Empire...
San Diego County deserts...San Diego County mountains...
Santa Ana Mountains and foothills.