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FXUS66 KSGX 161208 
  AFDSGX 
   
  Area Forecast Discussion 
  National Weather Service San Diego CA 
  408 AM PST Sat Dec 16 2017 
   
  .SYNOPSIS... 
  A trough of low pressure moving through Southern California today  
  will bring stronger onshore flow with cooling...more clouds...and with 
  gusty southwest to west winds in the mountains and deserts.  
  Surface high pressure over the Great Basin will bring offshore  
  flow with drying and with gusty north to northeast winds and lower 
  inland humidities for Sunday into Monday with the strongest winds 
  on Sunday. For Wednesday and Thursday...another low pressure  
  system moving southeastward through the Great Basin will bring  
  strong onshore flow with cooling...more clouds...and strong gusty 
  west winds in the mountains and deserts. Moderate to strong  
  offshore flow may follow for late Thursday into Friday with 
  periods of moderate to strong northeast winds. 
   
  && 
   
  .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... 
  SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO 
  COUNTIES... 
   
  .SHORT TERM (Today through Monday)... 
  A trough of low pressure is moving through Southern California 
  early this morning. This will bring stronger onshore flow with 
  significant cooling...more clouds...and gusty southwest to west 
  winds in the mountains and deserts. For inland coastal areas...the 
  valleys...and the mountains...high temperatures today will be 15  
  to 20 degrees cooler than on Friday...10 to 15 degrees cooler  
  towards the coast and in the upper deserts...and 5 to 10 degrees  
  cooler in the lower deserts. A brief return of lower level  
  moisture will bring slight chances for light showers...mainly for  
  central and southern coastal areas of San Diego for late morning  
  into the afternoon with any rainfall a few hundredths of an inch  
  at most.  
   
  The flow will turn offshore for tonight and Sunday with stronger 
  and gusty north to northeast winds developing along and below 
  coastal mountain slopes and below passes and canyons for portions 
  of San Bernardino...Riverside...and Orange Counties for late 
  tonight into Sunday morning with gusts to 50 mph and isolated 
  gusts to 60 mph. Weaker northeast winds will spread into the 
  mountains and inland valleys in San Diego County on Sunday. Winds 
  will weaken and become more localized for Sunday night and  
  Monday. High temperatures for coastal and valley areas will warm  
  on Sunday while the mountains and deserts continue to cool. The  
  warming will spread inland on Monday. 
   
  && 
   
  .LONG TERM (Tuesday through Friday)... 
  Warmer with weaker winds for Tuesday with weakening high pressure 
  aloft over California. A low pressure system off the Pacific 
  Northwest coast on Tuesday...will move into the Pacific Northwest 
  early Wednesday...and into the Great Basin late Wednesday and 
  Wednesday night. For Southern California...this will bring 
  stronger onshore flow with cooling for Wednesday into  
  Thursday...a possible return of the marine layer with night and  
  morning coastal low clouds and fog...and strong gusty west winds  
  in the mountains and deserts for Wednesday and Wednesday night. 
   
  For Thursday into Friday...upper level low pressure to the east 
  and surface high pressure over the Great Basin will bring periods 
  of moderate to strong northeast winds. There remain differences 
  with the location and strength of that upper level low pressure 
  among the global models along with the duration and strength of  
  the offshore flow. The ECMWF is weaker with the offshore flow  
  along with lesser duration of the offshore flow. The ECMWF also  
  advertises deamplification of the high amplitude pattern across  
  the mid latitudes of the eastern Pacific and North America for  
  early the week of Christmas. In between for next weekend...the  
  differences across Southern California are significant with some  
  global models maintaining closed upper level low pressure over  
  the southwest states and the ECMWF developing upper level high  
  pressure from the subtropical eastern Pacific into California. 
   
  && 
   
  .AVIATION...  
  161100Z...Areas of stratus will develop in coastal areas and extend  
  into the valleys and foothills of San Diego County starting 13Z-15Z  
  today. There is also a slight chance of -SHRA from the coast to the  
  foothills in San Diego County. Bases will be 1200-2500 ft MSL with  
  tops to 4000-5000 ft MSL. Clearing will occur 18Z-20Z in Orange  
  County but might not occur until 03Z-05Z this evening in parts of  
  San Diego County. After 05Z tonight, most areas will be clear, but  
  locally gusty northeast winds 15-30 knots with gusts 35-45 knots  
  will develop along southwest mountain slopes and through/below  
  passes and canyons, continuing Monday morning. Lighter winds will  
  occur in San Diego County.  
   
  && 
   
  .MARINE... 
  Combined seas could reach 8-9 feet in the outer waters tonight, just  
  below small craft advisory criteria, due to a WNW swell around 12  
  seconds. Otherwise, no hazardous marine weather is expected through  
  Wednesday. 
   
  && 
   
  .FIRE WEATHER... 
  Surface high pressure over the Great Basin will bring a period 
  of offshore flow for late tonight into Monday. Gusty north to 
  northeast winds will strengthen for late tonight across portions 
  of San Bernardino...Riverside...and Orange Counties and spread  
  southward into San Diego County on Sunday. The strongest winds are 
  expected across portions of San Bernardino...Riverside...and  
  Orange Counties for late tonight through Sunday morning with 
  lowest humidities for late Sunday morning through Sunday 
  afternoon. Winds are not expected to be as strong for San Diego 
  County with stronger winds and lower humidities mostly confined to 
  the coastal slopes of the mountains and the inland valleys. Winds 
  will weaken for Sunday night and Monday.  
   
  Another round of moderate to strong and gusty northeast winds is 
  possible for Thursday into Friday with low inland humidities. 
   
  && 
   
  .SKYWARN...  
  Skywarn activation is not requested. However weather spotters are 
  encouraged to report significant weather conditions. 
   
  && 
   
  .SGX WATCHES/WARNINGS/ADVISORIES... 
  CA...Fire Weather Watch from Sunday morning through Sunday evening  
       for San Diego County Inland Valleys-San Diego County  
       Mountains-Including The Palomar And Descanso Ranger  
       Districts of the Cleveland National Forest. 
   
       Red Flag Warning from 8 AM to 8 PM PST Sunday 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 Gorgonio Pass Near Banning-Santa Ana Mountains- 
       Including The Trabuco Ranger District of the Cleveland  
       National Forest. 
   
  PZ...NONE. 
   
  && 
   
  
 
 PUBLIC/FIRE WEATHER...17
 AVIATION/MARINE...Maxwell