100  
FXUS66 KSGX 270424  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
924 PM PDT WED JUN 26 2019  
   
SYNOPSIS
 
 
A PERSISTENT MARINE LAYER WILL HAVE LOW CLOUDS MOVE INLAND INTO  
THE VALLEYS EACH NIGHT AND CLEAR BACK TO NEAR THE COAST EACH DAY.  
A SLOW WARMING TREND WILL CONTINUE THROUGH THE WEEKEND. SOME MID  
AND UPPER LEVEL TROPICAL MOISTURE AND CLOUDS COULD SPREAD ACROSS  
PORTIONS OF FAR SOUTHERN CALIFORNIA AROUND SATURDAY. ANOTHER WEAK  
TROUGH OF LOW PRESSURE NEAR THE WEST COAST COULD SPREAD SLOW  
COOLING INLAND FOR THE EARLY TO MIDDLE PART OF NEXT WEEK WITH  
NIGHT AND MORNING COASTAL LOW CLOUDS EXTENDING FARTHER INTO THE  
VALLEYS.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
   
..UPDATE
 
 
THE COAST ENDED UP SEEING FULL SUNSHINE THIS AFTERNOON AS THE  
MARINE LAYER STRATUS DECK DISSIPATED. IT IS RE-DEVELOPING THIS  
EVENING IN PLACES ALONG THE COAST AND WILL CONTINUE TO DO SO AND  
SPREAD INTO WESTERN PORTIONS OF THE INLAND VALLEYS OVERNIGHT.  
DRIZZLE IS NOT ANTICIPATED TONIGHT AS THE MARINE LAYER WILL BE  
RATHER SHALLOW.  
 
WE HAVE BEEN LOOKING AT THE WEEKEND TO SEE IF REMNANT MOISTURE  
FROM TROPICAL STORM ALVIN COULD PRODUCE ANY RAINFALL OR ELEVATED  
CONVECTION (DRY LIGHTNING). ENSEMBLES SUPPORT A DRY FORECAST.  
INSTABILITY ON FORECAST SOUNDINGS IS VERY LOW WITH MUCAPE <50 J/KG.  
SO AT THIS TIME, WHILE MID-HIGH LEVEL MOISTURE WILL BE STREAMING  
IN FRIDAY NIGHT-SATURDAY, THE MAIN CONSEQUENCE LOOKS TO JUST BE  
SOME MID-HIGH LEVEL CLOUDINESS. HOWEVER, WE WILL CONTINUE TO  
ASSESS THIS AS THERE WILL BE A GOOD MOISTURE SURGE IN THE MID-  
UPPER LEVELS (RESULTING IN PW INCREASING TO 200-250% OF NORMAL,  
HIGHEST SE). SEE PREVIOUS DISCUSSION BELOW FOR FURTHER FORECAST  
DETAILS.  
   
..PREVIOUS DISCUSSION (ISSUED AT 134 PM PDT WED JUN 26 2019)
 
 
THIS AFTERNOON...THE MARINE LAYER LOW CLOUDS HAVE MOSTLY CLEARED  
OVER THE COASTAL AND INLAND AREAS EXCEPT FOR PORTIONS OF NORTHERN  
SAN DIEGO COUNTY AND SOUTHERN ORANGE COUNTY. THE LOW CLOUDS HAVE  
CLEARED MORE THAN YESTERDAY MOST LIKELY DUE TO A WEAKER INVERSION  
AND A THINNER CLOUD LAYER. THIS HAS RESULTED IN GENERALLY HIGHER  
TEMPS THAN AT THIS TIME YESTERDAY IN THE LOWER ELEVATIONS WEST OF  
THE MTNS. ELSEWHERE, TEMPS ARE ABOUT WHAT THEY WERE AT THIS TIME  
YESTERDAY OR EVEN A LITTLE LOWER IN SOME AREAS. THE HIGH CLOUDS  
FROM THIS MORNING HAVE MOVED OFF TO THE EAST.  
 
FROM PREVIOUS DISCUSSION...  
A LARGE LOW PRESSURE SYSTEM OFF THE COAST OF OR WITH A TROUGH  
EXTENDING SOUTHWARD OFF THE SOCAL COAST WILL DOMINATE OUR WEATHER  
INTO THE WEEKEND. FARTHER TO THE SOUTH, TROPICAL STORM ALVIN HAS  
DEVELOPED NEAR 14.7 DEGREES NORTH LATITUDE, 109.4 DEGREES WEST  
LONGITUDE.  
 
FOR THURSDAY INTO THE WEEKEND, THE AXIS OF THE LOW PRESSURE  
TROUGH WILL EXTEND FROM THE PACIFIC NORTHWEST COAST TO A POSITION  
OFF THE SOUTHERN CALIFORNIA COAST ALONG 130W. THIS WILL KEEP THE HIGH  
PRESSURE RIDGE TO THE SOUTHEAST EXTENDING FROM BAJA, ACROSS  
NORTHERN MEXICO, AND NEW MEXICO, INTO THE CENTRAL AND SOUTHERN  
PLAINS. SOUTHERN CALIFORNIA WILL BE IN BETWEEN WITH SOUTHWEST FLOW  
ALOFT AND CONTINUING ONSHORE FLOW.  
 
OVER TIME, THE TROUGH WILL WEAKEN AND HEIGHTS WILL RISE. THIS WILL  
CAUSE THE MARINE LAYER TO BECOME A LITTLE SHALLOWER WITH NIGHT  
AND MORNING COASTAL LOW CLOUDS NOT EXTENDING AS FAR INLAND. THIS  
WILL ALSO BRING SLOW WARMING FOR THURSDAY THROUGH THE WEEKEND.  
HOWEVER, IF MID AND HIGH LEVEL TROPICAL MOISTURE AND CLOUDS FROM  
THE REMNANTS OF ALVIN MOVES ACROSS PORTIONS OF THE AREA AROUND  
SATURDAY, HIGH TEMPERATURES COULD BE A LITTLE LOWER FOR THOSE  
AREAS ON SATURDAY. THERE IS ALSO SOME POTENTIAL FOR ELEVATED  
CONVECTION ACROSS PORTIONS OF THE AREA ON SATURDAY, MAINLY FOR THE  
AREAS CLOSER TO NORTHERN BAJA. IF THE TROUGH IS A LITTLE FARTHER  
EAST, THE MOISTURE WOULD MOSTLY STAY JUST SOUTH OF SOUTHWESTERN  
CALIFORNIA AS IT MOVES INTO ARIZONA. EVEN IF THE MID AND HIGH  
CLOUDS DO MATERIALIZE, CURRENT NUMERICAL MODEL GUIDANCE INDICATES  
THAT A LACK OF INSTABILITY AND FORCING WILL MAKE IT UNLIKELY FOR  
THERE TO BE SIGNIFICANT PRECIPITATION.  
 
FOR THE EARLY TO MIDDLE PART OF NEXT WEEK, ANOTHER WEAKER TROUGH  
OF LOW PRESSURE WILL APPROACH THE WEST COAST. THIS WOULD KEEP THE  
HIGH PRESSURE RIDGE SUPPRESSED TO THE SOUTHEAST. SLOW COOLING  
WOULD SPREAD INLAND WITH STRENGTHENING ONSHORE FLOW. THE MARINE  
LAYER WOULD ALSO DEEPEN WITH NIGHT AND MORNING COASTAL LOW CLOUDS  
AGAIN EXTENDING FARTHER INTO THE VALLEYS.  
 

 
   
AVIATION
 
 
270345Z...COAST/VALLEYS...SCT015-020 NEAR THE COAST THIS EVENING  
BECOMING BKN-OVC015-020 TOPS 030 AND MOVING 20 MILES INLAND THROUGH  
15Z THURSDAY. SKIES CLEARING BACK TO THE COASTAL TAF SITES THROUGH  
21Z. VIS RESTRICTIONS OF 2-5 MILES AT KONT AND KSBD FROM 13Z-18Z.  
 
MOUNTAINS/DESERTS...CLEAR SKIES WITH UNRESTRICTED VISIBILITY  
THROUGH THURSDAY.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE CONDITIONS THROUGH MONDAY.  
 

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

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
PZ...NONE.  

 
 

 
 
PUBLIC...GREGORIA (UPDATE)/PG (PREV DISCUSSION)  
AVIATION/MARINE...MOEDE  
 
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