Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 062118
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
118 PM PST Wed Dec 6 2017

.SYNOPSIS...
Santa Ana Winds will be strong at times through Saturday, with
the strongest winds likely Thursday. Very dry conditions will
prevail under mostly clear skies. There will be a warming trend
through the end of the week, with above normal temperatures each
day. Offshore flow will continue next week with very dry and warm
days and no prospect for rain.

&&

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

At 1 pm PST, water vapor satellite imagery displayed an upper-
level ridge stretching from British Columbia down to central
California, and a shortwave trough across northern Baja. A 1045
mb surface high over central Idaho and a 1019 mb surface low just
east of San Diego was creating east to northeast wind gusts of
35-45 mph through mountain passes and along coastal mountain
slopes. A Highest Wind Gusts PNS was issued late this morning with
the strongest observed wind gusts from last night through this
morning. It can be found on our social media web pages, or on our
Fastlinks page.

An upper-level trough moving by to our east tonight, combined with
surface offshore flow from the surface high over the Great Basin,
will create another round of strong east to northeast winds across
southwest CA tonight into Thursday. San Diego county will be the
main focus this time, with wind gusts along the coastal mountain
slopes and foothills forecast to be around 60 mph, and isolated
gusts around Sill Hill to near 90 mph. Winds will weaken Thursday
night into Friday, but remain strong. The High Wind Warning
remains in effect for the mountains, valleys and coastal Orange
County through Friday afternoon. The extremely dry airmass over
the area will continue afternoon relative humidity of 5-10% for
inland areas through next week. The ridge that is locked in over
CA for the time being will continue above normal high temperatures
for most areas through Thursday, with areas increasing to 5-15
degrees above normal this weekend into early next week.

The ridge will weaken and shift more westward by the middle of
next week, however above normal high temperatures, offshore flow
and the dry airmass is expected to continue through the period at
this time.

&&

.AVIATION...
062043Z...Through 07/0000 UTC, NE to E winds 15-30 kt with local
gusts 35-50 kt along the coastal mountain slopes/adjacent foothills
and through and below the passes and canyons today with associated
MOD-STG UDDFS/LLWS over and W or SW of the mountains. Gusty surface
NE to E winds will likely occur throughout the day at KONT and KSNA.
After 07/0000 UTC, NE to E winds will strengthen by 10-15 KT
resulting in STG-SVR UDDFS/LLWS and possible rotors over and W or SW
of the mountains. Otherwise, P6SM vis and SKC through Thursday
morning.

&&

.MARINE...
Offshore flow will strengthen again tonight and Thursday, with 25 to
30 kt easterly wind gusts possible across portions of the coastal
waters. A Small Craft Advisory has been issued for that time period.
No additional marine hazards are expected Friday through Monday.

&&

.FIRE WEATHER...
The Red Flag Warning has been extended through 8 pm Saturday as
critical to extreme fire weather conditions continue through the
period. Stronger winds are expected tonight through Thursday,
especially for portions of San Diego county which may see isolated
gusts near 90 mph. Strongest winds will continue to be below
mountain passes, along coastal mountain slopes and foothills. Weak
to moderate offshore flow will develop through early next week.
Minimum afternoon relative humidity of 5-10% will continue into
next week for inland areas, with relatively no overnight recovery
in the windy locations. High temperatures will increase 5-15
degrees above normal 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 from 10 PM this evening to 10 PM PST
     Thursday 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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