274  
FXUS66 KSGX 240237  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
737 PM PDT MON OCT 23 2017  
   
..AREAS OF STRONG GUSTY WINDS DEVELOPING OVERNIGHT
 
   
..RECORD-BREAKING HEAT AGAIN TUESDAY
 
 
   
SYNOPSIS
 
 
AREAS OF STRONG WINDS WILL DEVELOP OVERNIGHT THROUGH TUESDAY  
MORNING IN SANTA ANA STYLE. ANOTHER DAY OF RECORD-BREAKING HEAT IS  
FORECAST TUESDAY. HIGH PRESSURE WILL PREVAIL THROUGHOUT THE WEEK,  
BUT WILL WEAKEN. THIS WILL LEAD TO A GRADUAL MODERATION IN  
TEMPERATURES AND A RELAXATION OF THE SANTA ANA WINDS.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
   
..UPDATE
 
 
RECORD-BREAKING HEAT SCORCHED THE AREA TODAY WITH TRIPLE DIGIT  
READINGS OVER MUCH OF THE AREA. THE HOTTEST LOCATION WAS FULLERTON  
IN ORANGE COUNTY, HITTING 107F DEGREES. EXTREMELY DRY AIR WAS  
ENTRENCHED REGION WIDE WITH MIN RELATIVE HUMIDITY IN THE SINGLE  
DIGITS AND TEENS UNIFORM OVER ALL BUT THE IMMEDIATE COAST. PEAK  
SANTA ANA WINDS THIS MORNING WERE IN THE 40-50 MPH RANGE, EXCEPT  
SILL HILL IN SAN DIEGO COUNTY RECORDED A WIND GUST OF 57 MPH AT  
9 AM THIS MORNING.  
 
NOW TO THE FORECAST. THE MAIN HAZARDS WILL BE THE DEVELOPMENT OF  
STRONGER WINDS OVERNIGHT AND ANOTHER DAY OF RECORD-BREAKING HEAT  
ON TUESDAY.  
 
THE PRESSURE GRADIENT WILL TIGHTEN UP OVERNIGHT WITH -14MB  
PROJECTED FROM SAN DIEGO TO TONOPAH, NV. GLOBAL MODELS SHOW H85  
WINDS STRENGTHENING TO ABOUT 25 KT BY 12Z TUE. HI-RES MODELS SHOW  
STRONG WINDS DEVELOPING IN THE FAVORED WINDY LOCALES:  
THROUGH AND BELOW THE CAJON AND SAN GORGONIO PASS, THE SANTA ANA  
COASTAL FOOTHILLS (INLAND ORANGE COUNTY) AND THE COASTAL FOOTHILLS  
AND EASTERN INLAND VALLEYS OF SAN DIEGO COUNTY.  
 
CURRENT ASSESSMENT HAS WINDS STRONGER THAT WHAT OCCURRED THIS  
MORNING. THINKING IS WINDS BY TUE MORNING WILL PREVAIL OUT OF THE  
NORTHEAST (WINDS MORE ENE IN SAN DIEGO COUNTY) AT 20-35 MPH WITH  
PEAK GUSTS OF 50-60 MPH. SOME CITIES MOST LIKELY TO EXPERIENCE  
THE STRONGEST WINDS INCLUDE:  
 
ONTARIO, RANCHO CUCAMONGA, RIALTO, FONTANA, BEAUMONT, ALPINE AND  
RAMONA. PLACES LIKE SILL HILL AND FREEMONT CANYON COULD PEAK OUT  
AT AROUND 70 MPH.  
 
THE STRONGEST WINDS WILL OCCUR AT DAWN THROUGH ABOUT 10 AM  
TUESDAY, BUT WILL CONTINUE GUSTY IN CORRIDORS THROUGH THE  
AFTERNOON, ESPECIALLY THROUGH AND BELOW THE CAJON PASS EXTENDING  
THROUGH THE I.E. TO THE CENTRAL AND SOUTHERN ORANGE COUNTY COAST.  
ANOTHER POTENTIALLY FAVORED CORRIDOR OF GUSTIER ENE WINDS WILL BE  
FORM JUST WEST OF JULIAN THROUGH RAMONA TOWARDS ENCINITAS.  
 
THE HEAT WILL BE ON AGAIN TUESDAY WITH MORE RECORD HIGHS LIKELY.  
INCREASED TEMPERATURES ALONG THE COAST IN THIS UPDATE, ESPECIALLY  
FOR CENTRAL AND SOUTH ORANGE COUNTY TO ABOUT ENCINITAS. FURTHER  
SOUTH HI-RES MODELS SHOW A POTENTIAL WEAK EDDY WHICH COULD RESULT  
IN MORE ONSHORE WINDS OVER SOUTHERN SAN DIEGO COUNTY. TOUGH TEMP  
FORECAST FOR THE COAST. HIGHEST CONFIDENCE ON HOT BEACHES IS  
ACROSS CENTRAL AND SOUTHERN ORANGE COUNTY WHERE TEMPS SHOULD SOAR  
WELL INTO THE 90S. INLAND LOCALES WEST OF THE MOUNTAINS SHOULD BE  
SIMILAR TO WHAT OCCURRED TODAY DUE TO SIGNIFICANT ADIABATIC  
WARMING/COMPRESSIONAL HEATING ON DOWNSLOPE FLOW. MOUNTAIN LOCALES  
LIKELY WILL BE A FEW DEGREES COOLER AS TEMPS ALOFT NUDGE SLIGHTLY  
LOWER.  
   
..PREVIOUS DISCUSSION (ISSUED AT 153 PM PDT MON OCT 23 2017)
 
 
HOT AND VERY DRY WEATHER WILL CONTINUE THROUGH MID-WEEK WITH  
UPPER-LEVEL RIDGING ALOFT AND SURFACE HIGH PRESSURE OVER THE  
GREAT BASIN. H500 HEIGHTS WILL PEAK AROUND 595 DM THROUGH  
TOMORROW OVER SOUTHWEST CA. THIS WILL CREATE HIGH TEMPERATURES  
AROUND 10 DEG ABOVE NORMAL FOR DESERT AND MOUNTAIN LOCATIONS. THE  
DOWNSLOPING SANTA ANA WINDS WILL HELP CREATE HIGHS 15 TO 25 DEG  
ABOVE NORMAL FOR COASTAL AND VALLEY LOCATIONS THROUGH TUESDAY.  
SEVERAL HIGH TEMPERATURES RECORDS ARE EXPECTED TO BE BROKEN OR  
TIED OVER THE NEXT FEW DAYS. PLEASE SEE OUR WEATHER STORY ON OUR  
WEBPAGE FOR THE SPECIFIC TEMPERATURES AND RECORD INFORMATION. AN  
EXCESSIVE HEAT WARNING WILL CONTINUE FOR THE COASTS AND VALLEYS  
THROUGH TUESDAY FOR HIGHS IN THE LOW 100S INLAND, AND THE MID-80S  
TO MID-90S AT THE BEACH.  
 
GUSTY NORTHEASTERLY WINDS WILL CONTINUE THROUGH WEDNESDAY  
AFTERNOON IN THE MOUNTAINS, VALLEYS AND OVER MOST OF ORANGE  
COUNTY. SUSTAINED WINDS OF 15-30 MPH WITH GUSTS OF 40-60 MPH ARE  
POSSIBLE THROUGH THE PERIOD, WITH STRONGEST WINDS DEVELOPING  
TUESDAY MORNING THOUGH MOUNTAIN PASSES AND ALONG COASTAL MOUNTAIN  
SLOPES. A WIND ADVISORY REMAINS IN EFFECT THROUGH THE PERIOD.  
A RED FLAG WARNING ALSO REMAINS IN EFFECT THROUGH WEDNESDAY  
EVENING FOR EXTREMELY LOW RELATIVE HUMIDITY IN THE SINGLE DIGITS,  
GUSTY NORTHEASTERLY WINDS AND HOT WEATHER.  
 
THE RIDGE ALOFT WILL WEAKEN THROUGH THE END OF THE WEEK, BUT  
REMAIN OVER THE REGION. HIGH TEMPERATURES WILL LOWER TO JUST ABOVE  
SEASONAL NORMALS BY SATURDAY. RETURNING ONSHORE FLOW WILL  
INCREASE HUMIDITY ACROSS THE COAST AND VALLEYS BY THE END OF THE  
WEEK, AND ALSO CREATE THE POSSIBILITY OF LOW CLOUDS AND FOG ALONG  
THE IMMEDIATE COAST.  
 

 
   
AVIATION
 
 
240000Z...CLEAR WITH UNRESTRICTED VIS THROUGH TUESDAY EVENING. AREAS  
OF NORTHEAST TO EAST WINDS 15-25 KT AND GUSTS 35-45 KT WILL DEVELOP  
TONIGHT AND PEAK TUESDAY MORNING THROUGH MID-AFTERNOON. STRONGEST  
WINDS WILL BE THROUGH AND BELOW THE PASSES AND CANYONS, AND ON  
COASTAL MOUNTAIN SLOPES AND FOOTHILLS. THIS WILL PRODUCE MDT-STG  
UDDFS AND LLWS OVER AND W/SW OF THE MOUNTAINS, IMPACTING VCNTY KONT,  
KSBD, KRAL AND KSNA AT TIMES. WINDS WILL WEAKEN SLIGHTLY IN THE LATE  
AFTERNOON.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH FRIDAY.  
 

 
   
BEACHES
 
 
A COMBINATION OF WEST-NORTHWEST AND SOUTH SWELLS WILL BRING 3-6 FOOT  
SURF AT THE BEACHES OF ORANGE COUNTY AND SAN DIEGO COUNTY THROUGH  
WEDNESDAY, ALONG WITH A HIGH RIP CURRENT RISK.  
 

 
   
FIRE WEATHER
 
 
HIGH PRESSURE ALOFT AND SURFACE OFFSHORE FLOW WILL CREATE CRITICAL  
FIRE WEATHER CONDITIONS FOR AREAS OVER AND WEST OF THE MOUNTAINS  
THROUGH WEDNESDAY. NORTHEASTERLY WIND GUSTS OF 40-60 MPH ARE  
POSSIBLE FOR PORTIONS OF THE MOUNTAINS, VALLEYS AND AREAS OF  
ORANGE COUNTY, WITH STRONGEST WINDS OCCURRING TUESDAY MORNING  
ALONG COASTAL MOUNTAIN SLOPES. MINIMUM RELATIVE HUMIDITY WILL BE  
IN THE SINGLE DIGITS FOR MOST AREAS, WITH POOR OVERNIGHT RECOVERY.  
HIGH TEMPERATURES WILL RANGE FROM 10-25 DEG ABOVE NORMAL, AS WELL.  
A RED FLAG WARNING REMAINS IN EFFECT THROUGH WEDNESDAY EVENING.  
 

 
   
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 6 PM PDT WEDNESDAY 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-SAN GORGONIO PASS NEAR BANNING-  
SANTA ANA MOUNTAINS-INCLUDING THE TRABUCO RANGER DISTRICT  
OF THE CLEVELAND NATIONAL FOREST.  
 
WIND ADVISORY UNTIL 2 PM PDT WEDNESDAY FOR ORANGE COUNTY COASTAL  
AREAS-ORANGE COUNTY INLAND AREAS-RIVERSIDE COUNTY MOUNTAINS-  
SAN BERNARDINO COUNTY MOUNTAINS-SAN BERNARDINO AND  
RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SAN DIEGO COUNTY  
MOUNTAINS-SAN DIEGO COUNTY VALLEYS-SANTA ANA MOUNTAINS AND  
FOOTHILLS.  
 
EXCESSIVE HEAT WARNING UNTIL 8 PM PDT TUESDAY 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.  
 
PZ...NONE.  

 
 

 
 
PUBLIC...GREGORIA (UPDATE)/JJT (PREV DISCUSSION)  
AVIATION/MARINE...SS  
 
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