Area Forecast Discussion
Issued by NWS San Diego, CA

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371
FXUS66 KSGX 142151
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
151 PM PST Thu Dec 14 2017

.SYNOPSIS...
Santa Ana winds will continue at times through Sunday, with a
quick switch to onshore winds early Saturday. Above normal highs
will continue through Friday, then a bit cooler over the weekend
as the marine layer returns briefly. The ridge gradually weakens
and shifts a bit more to the west next week, allowing colder
systems from the north to enter the picture. They may bring a
little rain to northern portions of the state, with noticeable
cooling farther to the south as marine air returns.

&&

.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 centered around 400 miles west of Point Conception,
and an upper-level trough stretching from southern Baja to New
Mexico. A surface 1034 mb high over central Nevada and a 1014 mb
surface low over the California Bight was creating strong and
gusty winds over coastal mountain slopes and through and below
mountain passes. A PNS wind gust summary is headlined on our
webpage.

Gusty and locally strong Santa Ana winds will continue in the
aforementioned locations through Friday morning, with winds
becoming stronger in portions of San Diego County this afternoon
through tonight. East to northeast gusts to 50 mph are possible,
with isolated locations gusting 65 to 75 mph. Areas of blowing
dust will reduce visibility down to 3-5 miles at times. Winds
will weaken throughout the day Friday as offshore pressure
gradients weaken. High temperatures 5-15 degrees above normal
will continue through Friday with ridging aloft.

An upper-level trough will quickly move across the region from the
north on Saturday. This will help increase humidity, lower highs
closer to seasonal normals and temporarily switch winds back to
onshore. West wind gusts of 40-50 mph are possible along desert
mountain slopes Saturday morning. A few models have been hinting
at some shower development over the coastal waters near our region
Saturday morning. Due to the consistency of this, a slight chance
of thunderstorms has been added to the coastal waters for Saturday
morning.

Winds will switch back offshore behind the trough by late Saturday
afternoon for northern areas, and by Sunday morning for San Diego
County. East to northeast winds are not expected to be as strong
as they are today, however the strongest winds at this time look
to be more in Orange/San Bernardino/Riverside Counties, with gusts
of 40-60 mph possible in the usual windy locations. Confidence is
increasing that the persistent ridge will move to the west and
allow for troughing along the West Coast for mid to late next
week.

&&

.AVIATION...
142056...E to NE winds 15-25 kt with gusts 35-50 kt will continue
mainly in the foothills and through/below mountain passes through
15/0300 UTC resulting in LLWS and STG-SVR UDDFS/LLWS over and W or
SW of the mountains. 15/0300-1500 UTC, winds will weaken by about 10
KT and become less widespread, with MOD-STG UDDFS/LLWS over and W or
SW of the mountains. Otherwise, P6SM vis and SKC through Friday
morning.

&&

.MARINE...
No hazardous marine weather is expected through Tuesday.

&&

.FIRE WEATHER...
The Red Flag Warning currently in effect will continue through
Friday morning for inland areas with very low relative humidity
and gusty east to northeast winds. Winds will then weaken late
Friday and turn westerly early Saturday, then winds strengthen and
turn northeasterly late Saturday night through Sunday evening. A
Fire Weather Watch has been issued for the second Santa Ana event
expected on Sunday. Relative humidity will increase Saturday as an
upper-level trough moves across the region, then humidity drops
again Sunday with the offshore flow. Conditions will improve
Sunday night into early next week.

&&

.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 10 AM PST Friday for 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-San
     Gorgonio Pass Near Banning-Santa Ana Mountains-Including
     The Trabuco Ranger District of the Cleveland National
     Forest.

     Fire Weather Watch from late Saturday night through Sunday
     evening for 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-San Gorgonio Pass Near Banning-
     Santa Ana Mountains-Including The Trabuco Ranger District
     of the Cleveland National Forest.

PZ...NONE.
&&

$$

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



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