072  
FXUS66 KSGX 250428  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
926 PM PDT SAT SEP 24 2016  
   
SYNOPSIS
 
 
STRONG HIGH PRESSURE ALOFT OFF THE CALIFORNIA COAST AND SURFACE  
HIGH PRESSURE OVER THE GREAT BASIN WILL BRING DRY AND WARMER  
WEATHER THROUGH MONDAY WITH PERIODS OF GUSTY NORTHEAST WINDS NEAR  
THE COASTAL FOOTHILLS. HOTTEST DAYS AND STRONGEST WINDS ARE EXPECTED  
ON SUNDAY AND MONDAY. UPPER LEVEL LOW PRESSURE OVER THE SEA OF CORTES  
WILL BRING INCREASING MOISTURE AND SLOW COOLING FOR TUESDAY INTO  
WEDNESDAY. ONSHORE FLOW AND SEASONAL TEMPERATURES RETURN FOR THE  
LATTER HALF OF THE WEEK AS A DEVELOPING TROUGH MOVES INLAND OVER THE  
WESTERN STATES.  
 

 
   
EVENING UPDATE
 
 
A LARGE AREA OF UPPER HIGH PRESSURE WAS SITUATED OVER THE EASTERN  
PACIFIC THIS EVENING WITH AN UPPER LEVEL TROUGH DRAPED ACROSS THE  
ROCKY MOUNTAINS. LOCALLY, OFFSHORE GRADIENTS HAVE MAINTAINED 7-10 MB  
FROM THE COAST THE GREAT BASIN THIS EVENING. SKIES REMAIN CLEAR WITH  
SOME MODERATELY GUSTY OFFSHORE WINDS, BUT NOT QUITE REACHING WIND  
ADVISORY LEVELS YET.  
 
THE BIG WARMUP STARTED TODAY WITH MAX TEMPS TOPPING OUT ABOUT 10  
DEGREES ABOVE NORMAL. AS OFFSHORE FLOW MAXIMIZES ON SUNDAY,  
TEMPERATURES WILL BECOME MUCH WARMER AGAIN WEST OF THE MOUNTAINS,  
WITH OFFSHORE FLOW REACHING NEARLY TO THE COAST, TEMPS WILL SHOOT UP  
INTO THE 90S EVEN CLOSE TO THE COAST, WITH VALLEY TEMPERATURES  
APPROACHING 100 DEGREES. DIURNAL SEABREEZE SHOULD BRING SOME BRIEF  
RELIEF TO THE IMMEDIATE COAST DURING THE AFTERNOON.  
 
A FEW CHANGES WERE MADE TO THE ONGOING FORECAST THIS EVENING. NUMBER  
ONE CHANGE WAS TO TWEAK TEMPERATURES UP A BIT FOR SUNDAY, GIVEN THE  
LATEST TRENDS AND STRENGTH OF OFFSHORE EXPECTED, THEREFORE WE RAISED  
TEMPERATURES 2 TO 4 DEGREES WARMER FOR LOCATIONS WEST OF THE  
MOUNTAINS. THE OTHER CHANGE MADE THIS EVENING WAS TO GO AHEAD AND  
ADD A SLIGHT MENTION OF SHWRS/T-STORMS FOR TUE AND WED AFTERNOONS  
AND EVENINGS OVER THE MOUNTAINS. THE LATEST MODELS ARE IN AGREEMENT  
THAT ENOUGH MOISTURE AND INSTABILITY SHOULD BE PRESENT FOR A FEW  
TOWERS TO DEVELOP INTO CONVECTIVE CELLS.  
   
..REMAINDER OF PREVIOUS DISCUSSION
 
 
A STRONG 596 DM RIDGE OVER THE FAR EASTPAC WILL FORCE A TROUGH TO  
DIG SOUTH OVER THE SOUTHERN ROCKIES, THEN RETROGRADE WESTWARD OVER  
NW MEXICO THROUGH TUE. THIS WILL RESULT IN GENERAL SANTA ANA  
CONDITIONS OVER FAR SW CA, WITH GUSTY NORTHEAST WINDS ALONG THE  
FOOTHILLS, VERY LOW HUMIDITY, AND HOT DAYS WEST OF THE MTS THROUGH  
MONDAY.  
 
THE EASTERLY FLOW GENERATED BY THE LOW TO THE SOUTH WILL EVENTUALLY  
PICK UP SOME MOISTURE AND DRIVE IT WEST ACROSS THE REGION, RAISING  
THE HUMIDITY AND POSSIBLY GENERATING A FEW CLOUDS. THIS WILL ALSO  
RESULT IN A SLOW COOLING TREND WHICH WILL BE FURTHER ENHANCED BY A  
DEVELOPING TROUGH ALONG THE WEST COAST LATE IN THE WEEK.  
 
NUMEROUS PRODUCTS ARE IN EFFECT INCLUDING A HEAT ADVISORY WEST OF  
THE MTS...WIND ADVISORIES FOR THE MTS/VALLEYS...A RED FLAG  
WARNING...AND A BEACH HAZARD STATEMENT. PLEASE SEE LAXNPWSGX...THE  
FIRE WEATHER DISCUSSION BELOW...AND LAXCFWSGX FOR DETAILS.  
 
THERE IS A SMALL CHANCE THAT THE MOISTURE ASSOCIATED WITH THE CUT-  
OFF LOW TO THE SOUTH COULD GENERATE A FEW SHOWERS TUE INTO WED, BUT  
THE CHANCE LOOKS TOO SLIM AT THIS POINT TO INCLUDE IN THE FORECAST.  
TEMPERATURES SHOULD BE BACK TO AVERAGE BY MIDWEEK AND FALL BELOW  
AVERAGE NEXT WEEKEND.  
 

 
   
AVIATION
 
 
250300Z...LOCAL N TO NE WINDS GUSTING 20 TO 25 KT ACROSS THE COASTAL  
MOUNTAIN RIDGES COULD PRODUCE MODERATE LOW LEVEL WIND SHEAR WITH UP  
AND DOWNDRAFTS THIS EVENING. HOWEVER, STARTING AROUND 250800Z WINDS  
WILL INCREASE FROM THE NORTHEAST THROUGH SUNDAY, PEAKING MONDAY FOR  
KSAN. THE INCREASING WINDS COULD PRODUCE IMPACTS FOR KONT, KSAN AND  
KSNA WITH MDT TO STRONG LLWS AND UP/DOWN DRAFTS. CONFIDENCE IS  
MODERATE TO HIGH FOR OCCURRENCE, BUT LOW TO MODERATE FOR TIMING OF  
IMPACTS AT TAF LOCATIONS.  
 
OTHERWISE, A FEW HIGH CLOUDS AND UNRESTRICTED VIS THROUGH MONDAY  
EVENING ACROSS THE FORECAST AREA.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH WEDNESDAY.  
 

 
   
BEACHES
 
 
BEACH HAZARD STATEMENT IS IN EFFECT...WITH A LONG-PERIOD SOUTH SWELL  
FROM 200-220 DEGREES CREATING ELEVATED SURF OF 4 TO 6 FT WITH  
OCCASIONAL HIGHER SETS ALONG SOUTHWEST-FACING BEACHES IN ORANGE  
COUNTY. SURF OF 3 TO 5 FT IS POSSIBLE ALONG SELECT, SOUTHWEST FACING  
SAN DIEGO COUNTY BEACHES NORTH OF CARLSBAD. STRONG AND DANGEROUS RIP  
CURRENTS ARE EXPECTED WITH THE ELEVATED SURF. SWELL AND SURF WILL  
SUBSIDE SUNDAY EVENING.  
 

 
   
FIRE WEATHER
 
 
WEATHER CONDITIONS WILL DETERIORATE THROUGH SUNDAY AS OFFSHORE FLOW  
INCREASES AND DRIVES RH VALUES DOWN ALONG AND WEST OF THE MOUNTAINS.  
THE COMBINATION OF WIND AND LOW RH HAS PROMPTED A RED FLAG WARNING  
FROM LATE TONIGHT INTO MONDAY AFTERNOON FOR ALL AREAS EXCEPT THE  
COASTAL STRIP. NORTHEAST TO EAST WINDS WILL BE STRONGEST THROUGH AND  
BELOW THE WIND-PRONE PASSES, AND AREAS OF THE COASTAL SLOPES AND  
ADJACENT FOOTHILLS WHERE LOCAL GUSTS OF 45 TO 55 MPH ARE POSSIBLE.  
FOR THE REMAINDER OF THE VALLEY AREAS AND INLAND ORANGE COUNTY,  
EXPECT NORTHEAST TO EAST WINDS OF 15-25 MPH WITH HIGHER GUSTS AT  
TIMES. RH WILL BE AROUND 8 TO 12 PERCENT ON SUNDAY, INCREASING TO 12  
TO 20 PERCENT ON MONDAY. ONLY MODEST OVERNIGHT RECOVERY IS  
ANTICIPATED WITH THE LEAST NEAR THE WIND PRONE FOOTHILLS.  
 
THE WINDS ARE EXPECTED TO DECREASE A BIT NORTH OF RIVERSIDE COUNTY  
ON MONDAY, BUT REMAIN QUITE STRONG OVER SAN DIEGO COUNTY. ALSO, ON  
MONDAY, RH WILL BE INCREASING FROM THE EAST. MOST AREAS SHOULD BE  
ABOVE THE 15 PERCENT THRESHOLD LATE IN THE DAY AS THE WINDS BEGIN TO  
DECREASE.  
 
WEAKER OFFSHORE FLOW WILL CONTINUE INTO TUESDAY AND WEDNESDAY AS  
HUMIDITY AND HEAT MODERATE.  
 

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

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...RED FLAG WARNING FROM MIDNIGHT TONIGHT TO 3 PM PDT MONDAY FOR  
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-SAN GORGONIO PASS NEAR BANNING-  
SANTA ANA MOUNTAINS-INCLUDING THE TRABUCO RANGER DISTRICT  
OF THE CLEVELAND NATIONAL FOREST.  
 
WIND ADVISORY FROM MIDNIGHT TONIGHT TO 5 PM PDT MONDAY FOR SAN  
DIEGO COUNTY MOUNTAINS-SAN DIEGO COUNTY VALLEYS.  
 
WIND ADVISORY FROM MIDNIGHT TONIGHT TO 4 PM PDT SUNDAY FOR  
ORANGE COUNTY INLAND AREAS-RIVERSIDE COUNTY MOUNTAINS-SAN  
BERNARDINO COUNTY MOUNTAINS-SAN BERNARDINO AND RIVERSIDE  
COUNTY VALLEYS-THE INLAND EMPIRE-SANTA ANA MOUNTAINS AND  
FOOTHILLS.  
 
HEAT ADVISORY FROM 11 AM SUNDAY TO 8 PM PDT MONDAY FOR ORANGE  
COUNTY COASTAL AREAS-ORANGE COUNTY INLAND AREAS-SAN  
BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-  
SAN DIEGO COUNTY COASTAL AREAS-SAN DIEGO COUNTY VALLEYS-  
SANTA ANA MOUNTAINS AND FOOTHILLS.  
 
BEACH HAZARDS STATEMENT THROUGH SUNDAY EVENING FOR ORANGE COUNTY  
COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.  
 
PZ...NONE.  

 
 

 
 
PUBLIC/FIRE WEATHER...JAD/JMB  
AVIATION/MARINE/BEACHES...PG  
 
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