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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 152104
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Mon Oct 15 2018

.SYNOPSIS...
Upper level low pressure over Arizona and surface high pressure over 
the Great Basin will continue the strong gusty northeast winds 
through Tuesday, though a little weaker than those of today. Periods 
of weaker and more localized northeast winds are expected Wednesday 
through Friday. Most areas will be gradually warmer Tuesday through 
Saturday. Upper level low pressure could move west off the Southern 
California coast and draw some moisture into portions of Southern 
California and result in a chance of showers and thunderstorms over 
the weekend.

&&

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

The Santa Ana Winds have arrived in most areas, with strongest winds 
in Orange County and the Inland Empire. Highest recorded gust has 
been 82 MPH at Fremont Canyon, with numerous locations having gusts 
over 55 MPH. The last of the remaining cumulus was dissipating over 
southern San Diego County early this afternoon due to the drying of 
the 700 MB layer. The winds should gradually decrease this afternoon 
and evening, with a smaller and more localized peak in the winds 
late tonight and Tuesday morning as the inversion which was a little 
above 700 MB will likely lower to around 800 MB tonight, which will 
restrict the strong winds to the coastal mountain slopes with much 
less wind near the coast and even in many of the valleys. Humidity 
is much lower across the region, below 20 percent in most areas at 
early afternoon, with some below 10 percent. Temperatures are a 
mixed bag as compressional heating resulted in warming at lower 
elevations (mostly 70s to mid 80s) but cold air advection brought 
cooling to higher elevations, with Blue Ridge at over 8000 feet 
elevation still only 33 degrees, and most other mountain locations 
in the 40s and 50s.

The upper low moving into Arizona will meander over that area 
through late week with a piece of the low moving west towards 
coastal southern California by the weekend. Some moisture will wrap 
around the low, with a likely increase in clouds, probably cumulus, 
Wednesday, then perhaps enough moisture and instability this weekend 
for showers and thunderstorms. With the low-level east flow, chances 
will be best from the mountains east to the deserts, but enough 
moisture could spread west of the mountains, even with the 
downsloping winds, to produce a few showers or thunderstorms there. 
Temperatures will increase in most areas Tuesday with warm weather 
continuing through the weekend, possibly in the lower 90s in some 
locations by Saturday west of the mountains. The only exception 
would be any places along the coast that get westerly low-level 
return flow, which should happen each afternoon Tuesday through at 
least Friday. The offshore flow, based on current model projections, 
could actually increase Saturday, but nowhere near the strength of 
today.

&&

.AVIATION... 
152030Z....Main issue this forecast period will be winds. The 
foothills, adjacent valleys and portions of Orange County including 
KONT, KSBD, and KSNA are seeing winds of 20-30 kts with gusts 40-50 
kts. STG-SVR Up/downdrafts likely over and S/SW of the mountains. 
Winds will begin to decrease after 22Z and continue to subside to 5-
15 knots by late evening over the terminals. Winds will increase 
again Tuesday morning for a few hours, but not as strong or 
widespread as today. For the lower deserts including KPSP/KTRM will 
see northwest winds of 15-25 kts through the period. No issues with 
marine layer stratus this period.  

&&

.MARINE...
Expect gusty northeast winds to 25 knots over the northern coastal 
waters mainly within the stretch between Camp Pendleton and San 
Clemente Island through early this evening. These intermittent gusts 
to 25 KT will be briefly hazardous to small craft through this 
afternoon. No hazardous marine weather is expected from later 
tonight through Friday.


&&

.FIRE WEATHER...
Critical fire weather conditions will continue through Tuesday with 
periods of gusty northeast to east winds and much lower humidity. 
Lowest humidity inland will fall to 5 to 10 percent this afternoon 
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 
20 to 35 mph with gusts to 60 mph, diminishing some to 20 to 30 mph 
with gusts to 45 mph late this afternoon through Tuesday. In 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 this afternoon, lowering a bit 
tonight and Tuesday.

Weaker and less widespread northeast winds are expected Wednesday 
through Friday with a slow recovery of humidity. Northeast winds 
could increase again Saturday, though not as strong as those of 
today.

&&

.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 Coastal Areas-Orange County Inland Areas-San 
     Bernardino County Mountains-San Bernardino and Riverside 
     County Valleys-The Inland Empire-Santa Ana Mountains and 
     Foothills.

     Wind Advisory until 6 PM PDT this evening for San Diego County 
     Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...Maxwell
AVIATION/MARINE...Moreland