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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 162048
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
148 PM PDT Tue Oct 16 2018

.SYNOPSIS...
Offshore flow will weaken through this evening with northeast 
winds not as strong and widespread as on Monday. Periods of 
weaker northeast winds will continue at times into the weekend. 
Areas near the coast will cool a little through Thursday, with 
inland warming into Saturday. For Sunday into Monday, a weak upper
level low pressure system off the southern California coast could
bring increasing clouds and a slight chance of showers and 
thunderstorms.

&&

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

This afternoon...Temperatures are generally higher than at this 
time yesterday, except for the San Diego County coastal areas. 
Single-digit humidities extend almost to the immediate coast as 
offshore flow continues. The offshore flow is weakening as sfc 
pressure gradients continue to trend weaker offshore. The winds 
have peaked and are diminishing, with only one location reporting 
wind gusts to 50 mph at this hour.

From previous discussion...
Through Thursday...The upper level low pressure centered over 
Arizona will slowly weaken and be centered over Utah by Thursday.
A the same time, the sfc high over the Great Basin will move
eastward. This will result in weakening offshore flow across 
southern California.

The northeast winds will mostly diminish during the afternoon. 
Periods of weaker and more localized northeast winds will continue
for Wednesday and Thursday. 

With the weakening offshore flow and decreasing lower level cold
advection from the Great Basin, high temperatures near the coast
will decrease a little today and Wednesday while areas farther 
inland warm several degrees today and a few more degrees on 
Wednesday. High temperatures on Thursday will be even a degree or
two warmer.

Friday through Monday...Weak upper level low pressure will 
develop off the southern California coast on Friday and remain 
through Sunday, then begin to move slowly inland on Monday. The 
upper level low pressure could draw some mid level moisture 
westward into portions of southern and central California for 
Saturday night into Monday. Model solutions continue to favor 
relatively greater chances for showers and isolated thunderstorms 
for San Bernardino, Riverside, and Imperial Counties and lesser 
chances for areas farther west. 

Some additional warming is expected for Friday and Saturday with 
continuing mostly weak offshore low level flow with gusty 
northeast winds near the coastal foothills. For Sunday into 
Monday, greater cloud cover would bring some cooling. 

There is less cold air aloft with this low pressure system than
with the one at the end of last week. High temperatures on Sunday
and Monday should be closer to seasonal averages than last 
Saturday and there should be less potential for thunderstorms than
last Friday night and Saturday.

Chances for precipitation decrease as the upper low moves
northeast late Monday into Tuesday.

&&

.AVIATION... 
162030z... Clear skies expected through tonight. Winds are remaining 
gusty at this hour, especially at KONT, KSBD, KPSP and KTRM with 15-
20 KT winds and gusts to 30KT. Winds will begin to weaken after 22Z 
this evening, and continuing to diminish tonight. LLWS possible this 
evening around 00-04Z as winds diminish. MOD UDDFS on coastal 
mountain slopes through this evening. Coastal low clouds will not be 
an issue tonight through Wed morning.

&&

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

&&

.FIRE WEATHER...
The Red Flag Warning continues through 8 PM this evening for the
mountains, valleys, and Orange County. Critical fire weather 
conditions will continue with periods of gusty northeast to east 
winds and very low humidity.

Northeast winds will weaken during the afternoon and evening. 
Humidities of 10 percent or less will begin to recover tonight and
gradually increase through Thursday as the offshore winds weaken.

&&

.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 this evening 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.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...PG
AVIATION/MARINE...Connolly/JJT