Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 071813
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1013 AM PST Thu Dec 7 2017

.SYNOPSIS...
Santa Ana winds will be strong at times through Friday, with the
strongest winds likely this morning. Very dry conditions will
prevail through the middle of next week. High temperatures will
increase to 5-15 degrees above normal by the weekend, and
continue into next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

At 9 AM PST, water vapor satellite imagery displayed an upper-
level ridge stretching from central CA, all the way up to
southern British Columbia. A 13.2 mb offshore surface pressure
gradient from San Diego to Tonopah was creating east to northeast
wind gusts of 40-60 mph along coastal mountain slopes and
foothills, with a few areas gusting around 75 mph. Peak gust so
far this morning was 88 mph at Sill Hill. Check out our PNS for
the highest observed gusts as of 9 AM. An extremely dry airmass is
in place over San Diego County this morning, with widespread
locations calculating relative humidity below 5%.

Winds will peak over the next few hours, with stronger winds
surfacing over portions of the valleys and coast by late morning.
Winds will weaken slightly overnight, but remain gusty through
Friday afternoon. A High Wind Warning remains in effect for the
mountains, valleys, San Gorgonio Pass and all of Orange County
through 4 pm Friday. The surface high over the Great Basin will
weaken by this weekend, however breezy to gusty offshore winds
will continue for inland areas through the middle of next week.
Upper-level heights building over the region will create high
temperatures 5-15 degrees above seasonal normals through the
middle of next week.

Models are in disagreement in the placement of the upper-level
ridge for the end of next week, with some showing the ridge
anchored over SoCal, and some showing it well off the West Coast.
No sign of low stratus or precipitation for the next 7 days.

&&

.AVIATION...
071645Z...NE to E winds 25-40 kt with gusts 45-60 kt along the
coastal mountain slopes/foothills and through and below the passes
and canyons through 08/0000 UTC, resulting in STG-SVR UDDFS/LLWS and
possible rotors over and W or SW of the mountains. Strong winds will
likely continue at KONT (greater than 45 kt gusts) and KSNA (greater
than 30 kt gusts), and KCRQ and KSAN will probably get some gusty NE
surface winds at some point. Winds a little weaker and less
widespread 08/0000-1500 UTC, with STG UDDFS/LLWS over and W or SW of
the mountains. Local vis 3-6 SM in BLDU possible in the wind prone
areas. Otherwise, P6SM vis and mostly SKC through Friday morning.

&&

.MARINE...
Areas of strong and intermittent easterly winds will occur today
over the coastal waters. Gusts in those windy areas will reach 25 to
30 kt at times. A Small Craft Advisory remains in effect until 10 PM
tonight. No additional marine hazards are expected Friday through
Monday.

&&

.FIRE WEATHER...
Extreme fire conditions are taking place this morning, with areas
near the mountains and foothills experiencing wind gusts of 40-60
mph, and relative humidity below 5%. A few areas are gusting 75-85
mph this morning. Highest winds are expected before 1200 today,
with winds slightly weakening through the weekend. The dry
airmass is expected to remain in place for inland areas through at
least the middle of next week. The Red Flag Warning currently in
effect goes through 8 pm Saturday, however an extension through
Sunday may be needed do to winds remaining strong and critical
fire weather conditions continuing. High temperatures will
increase to 5-15 degrees above seasonal normals by the weekend.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning until 4 PM PST Friday for Orange County
     Coastal Areas-Orange County Inland Areas-Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains-San Diego County Valleys-San Gorgonio Pass
     Near Banning-Santa Ana Mountains and Foothills.

     Red Flag Warning until 8 PM PST Saturday 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 Coastal Areas-San Diego County Inland
     Valleys-San Diego County Mountains-Including The Palomar
     And Descanso Ranger Districts of the Cleveland National
     Forest-San Gorgonio Pass Near Banning-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

PZ...Small Craft Advisory until 10 PM PST this evening for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm-Waters from San Mateo point to the Mexican Border
     Extending 30 to 60 nm out including San Clemente Island.

&&

$$

PUBLIC/FIRE WEATHER...JJT
AVIATION/MARINE...Harrison



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