733  
FXUS66 KSGX 171625  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
925 AM PDT SAT AUG 17 2019  
   
SYNOPSIS
 
 
COOLER WEATHER THIS WEEKEND WILL TURN VERY HOT INLAND NEXT WEEK  
AS HIGH PRESSURE BUILDS OVER THE SOUTHWEST. AT THE SAME TIME,  
COASTAL LOW CLOUDS MAKING AN APPEARANCE IN THE VALLEYS DURING  
NIGHTS AND MORNINGS WILL RETREAT TO THE COAST.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
LOW PRESSURE ALOFT FINALLY MADE ITS PRESENCE FELT AT THE SURFACE  
OVERNIGHT AS THE MARINE LAYER DEEPENED CONSIDERABLY. A MARINE  
LAYER THAT WAS AROUND 1200 FEET DEEP FRIDAY MORNING QUICKLY  
DEEPENED TO ABOUT 2200 FEET THIS MORNING. THAT ALLOWED LOW CLOUDS  
TO MOVE AS FAR INLAND AS SAN BERNARDINO AND HEMET, AND NEARLY  
FILL THE ENTIRE COASTAL BASIN. TODAY WILL BE MOSTLY SUNNY AS MANY  
OF THOSE CLOUDS HAVE ALREADY CLEARED. A SIMILAR MARINE LAYER AND  
LOW CLOUD COVERAGE IS EXPECTED TONIGHT INTO SUNDAY. THE LOW  
PRESSURE ALOFT WILL LIFT OUT AND HIGH PRESSURE FROM THE EAST WILL  
GRADUALLY PRESS DOWN OVER THE SOUTHWEST. THAT WILL BRING US A  
NOTABLE WARMING TREND STARTING MONDAY THAT WILL PEAK IN A HEAT  
WAVE WEDNESDAY AND THURSDAY VERY SIMILAR TO THE ONE WE HAD THIS  
PAST WEEK. HIGH TEMPERATURES THIS WEEKEND WILL COME IN BELOW  
AVERAGE, BUT WILL CLIMB ABOVE AVERAGE INLAND BY TUESDAY AND 5-10  
DEGREES ABOVE AVERAGE ON WEDNESDAY AND THURSDAY, THE PROJECTED  
HOTTEST DAYS. THE HIGH PRESSURE ALOFT WEAKENS EVER SO SLIGHTLY  
THURSDAY INTO NEXT WEEKEND. TEMPS WILL BEGIN A MODEST DECREASE,  
ALTHOUGH IT WILL STILL BE PLENTY HOT INLAND. MONSOON MOISTURE  
BEGINS TO SHOW ITSELF TOWARD NEXT WEEKEND, BUT NOTHING TO REALLY  
FORECAST ABOUT YET.  
 

 
   
AVIATION
 
 
171530Z...COAST/VALLEYS...AT 15Z, WIDESPREAD LOW CLOUDS WITH BASES  
AROUND 1500 FT MSL AND TOPS TO 2500 FT MSL, EXTENDING UP TO 30 MI  
INLAND AFFECTING ALL TAF SITES WEST OF THE MTNS. LOCAL VIS 1-3 MILES  
WHERE CLOUDS AND TERRAIN INTERSECT. EXPECT CLEARING AT KONT AND KSBD  
AROUND 16Z, AND AT COASTAL TAF SITES BETWEEN 17Z AND 18Z. LOW CLOUDS  
LIKELY RETURNING TO COASTAL TAF SITES BETWEEN 03Z AND 06Z WITH BKN-  
OVC BASES AROUND 1500 FT MSL AND TOPS TO 2500 FT MSL, SPREADING UP  
TO 30 MILES INLAND OVERNIGHT. CIGS AND REDUCED VIS COULD REACH KONT  
AND KSBD BETWEEN 12Z AND 15Z SUNDAY.  
 
MOUNTAINS/DESERTS...SCT CLOUDS AT OR ABV 20000 FT MSL AND  
UNRESTRICTED VIS THROUGH SUNDAY. W WINDS GUSTING 25-40 KT OVER MTN  
CRESTS AND THROUGH PASSES, PRODUCING WEAK TO MDT UP/DOWNDRAFTS AND  
LLWS OVER AND EAST OF THE MTNS BETWEEN 19Z SAT AND 12Z SUN. NO  
IMPACTS EXPECTED AT KPSP AND KTRM.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH WEDNESDAY.  
 

 
   
SKYWARN
 
 
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE  
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.  
 

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...EXCESSIVE HEAT WATCH FROM TUESDAY MORNING THROUGH THURSDAY  
EVENING FOR APPLE AND LUCERNE VALLEYS-COACHELLA VALLEY-SAN  
DIEGO COUNTY DESERTS-SAN GORGONIO PASS NEAR BANNING.  
 
PZ...NONE.  
 

 
 

 
 
PUBLIC...MM  
AVIATION/MARINE...PG  
 
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