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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 151241
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
541 AM PDT Mon Oct 15 2018

.SYNOPSIS...
Upper level low pressure over Arizona and surface high pressure
over the Great Basin will bring periods of strong gusty northeast 
winds today, with winds not as strong for tonight and Tuesday. 
The strongest winds are expected for Orange County and the 
mountains and valleys of San Bernardino and Riverside Counties 
with damaging wind gusts possible this morning. Periods of weaker
and more localized northeast winds are expected for Wednesday
through Friday. Coastal areas will warm and inland areas will 
cool for today. For Tuesday through Friday, coastal areas will 
cool while inland areas warm. For next weekend, upper level low 
pressure centered off the Southern California coast could draw 
some moisture into portions of Southern California with a chance 
of showers and thunderstorms for late Saturday into Sunday.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
 
Upper level low pressure moving southward through far southern
Nevada and the eastern deserts of Southern California will move
into western Arizona today. Northeast winds aloft behind this
trough of low pressure and surface high pressure over the Great
Basin will bring periods of strong and gusty northeast winds
today. The strongest winds are expected from the coastal mountain
slopes of the San Bernardino and Riverside Counties westward to
the Orange County coast with winds of 30 to 40 mph with gusts to
60 mph. Isolated gusts to 80 mph are expected below passes and
canyons and near the coastal slopes of the Santa Ana Mountains.
The winds are not expected to be as strong in San Diego County 
with strongest and most widespread winds of 20 to 30 mph with 
gusts to 45 mph in the mountains and inland valleys. 

Periods of northeast winds will continue tonight and Tuesday but
are not expected to be as strong and not quite as widespread.
Lowest inland humidity will fall to 5 to 10 percent today and
around 10 percent on Tuesday. 

Cold advection behind the trough of low pressure will bring
cooling for the mountains, deserts, and inland valleys today with
downslope warming from the western valleys to the coast with
high temperatures near the coast around 10 degrees warmer than on
Sunday. Inland areas will warm for Tuesday through Friday as the 
offshore flow weakens.

For next weekend, the GFS and ECMWF are in better agreement in 
placing the center of closed upper level low pressure off the 
Southern California coast. In this position, the low could draw 
some moisture from the east into portions of Southern California. 
Current model runs have the greatest precipitation coverage in 
Southern California across San Bernardino, Riverside, and Imperial
Counties for late Saturday through early Sunday with the local 
extended run of the WRF having some additional diurnal convection 
for the mountains and inland valleys on Sunday afternoon. Slight 
chance PoPs for showers and thunderstorms have been introduced for
some areas for late Saturday into Sunday for now.

&&

.AVIATION... 
150900Z....Scattered coastal low clouds will disappear by 14Z. 
Scattered to broken clouds at about 6000-8000 feet msl will 
gradually clear by 19-20Z. Northeast winds will continue to 
strengthen this morning and peak between 15-20Z at 20-40 KT with 
gusts 40-60 KT, particularly in foothills, adjacent valleys and 
Orange County. LLWS anywhere west of the mountains until these winds 
surface. Strongest winds between Cajon Summit and Orange County. STG-
SVR Up/downdrafts likely over and S/SW of the mountains. Winds will 
decrease some this afternoon and evening, but continue rather strong 
through Tuesday morning. 

&&

.MARINE...
Gusty northeast winds mainly near Camp Pendleton this morning, but 
also intermittently anywhere within the stretch between Camp 
Pendleton and San Clemente Island. These intermittent gusts to 25 KT 
or higher would be briefly hazardous to small craft through about 
midday. Lighter winds south of a line from Oceanside to south San 
Clemente Island. No hazardous marine weather is expected this 
afternoon through Friday.

&&

.FIRE WEATHER...
Critical fire weather conditions will develop this morning and
continue through Tuesday with periods of gusty northeast to east
winds and much lower humidity. Lowest humidity for inland areas
will fall to 5 to 10 percent today and around 10 percent Tuesday
with poor overnight recovery. For San Bernardino, Riverside, and
Orange Counties from the coastal slopes of the mountains to the
coast, widespread northeast to east winds of 30 to 40 mph with
gusts to 60 mph are expected for this morning, diminishing some to
20 to 30 mph with gusts to 45 mph for tonight and Tuesday. 
Isolated gusts to 80 mph are possible this morning, mainly below 
passes and canyons and near the coastal slopes of the Santa Ana 
Mountains. For San Diego County, the strongest northeast to east 
winds are expected from the coastal mountain slopes into the 
inland valleys with winds of 20 to 30 mph with gusts to 45 mph.

Weaker and less widespread northeast winds are expected for
Wednesday through Friday with a slow recovery of humidity for
inland areas.

&&

.SKYWARN... 
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 8 PM PDT Tuesday for Orange County 
     Coastal Areas-Orange County Inland Areas-Riverside County 
     Mountains-Including The San Jacinto Ranger District Of The 
     San Bernardino National Forest-San Bernardino County 
     Mountains-Including The Mountain Top And Front Country 
     Ranger Districts Of The San Bernardino National Forest-San 
     Bernardino and Riverside County Valleys  -The Inland Empire-
     San Diego County Inland Valleys-San Diego County Mountains-
     Including The Palomar And Descanso Ranger Districts of the 
     Cleveland National Forest-Santa Ana Mountains-Including The 
     Trabuco Ranger District of the Cleveland National Forest.

     Wind Advisory until 8 PM PDT this evening for Coachella Valley-
     San Diego County Deserts-San Gorgonio Pass Near Banning.

     High Wind Warning until 3 PM PDT this afternoon for Orange 
     County Inland Areas-San Bernardino County Mountains-San 
     Bernardino and Riverside County Valleys-The Inland Empire-
     Santa Ana Mountains and Foothills.

     Wind Advisory from 6 AM this morning to 6 PM PDT this evening 
     for San Diego County Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...17
AVIATION/MARINE...MM