308
FXUS66 KSGX 091849
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
1149 AM PDT SUN AUG 9 2026
SYNOPSIS
MINOR TO MODERATE HEATRISK CONTINUES THROUGH MONDAY WITH COOLER
WEATHER TUESDAY AND BEYOND. THUNDERSTORM CHANCES EACH DAY IN THE
MOUNTAINS THROUGH WEDNESDAY, WITH BEST CHANCES AND HIGHEST RAIN
RATES MONDAY AND TUESDAY. PATCHY COASTAL FOG MONDAY MORNING WITH A
DEEPENING MARINE LAYER THROUGH THE END OF THE WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SATELLITE SHOWS HIGH CLOUDS STREAMING INTO RIVERSIDE AND SAN
BERNARDINO COUNTIES FROM THE SOUTHEAST AFTER A COLLAPSED MCS THIS
MORNING, ALTHOUGH ANY PRECIPITATION DIED OFF BEFORE REACHING OUR
BORDERS. MUCH OF THE HIGH CLOUDS SHOULD MOVE OUT BY THE AFTERNOON,
AND HIGH PRESSURE SITUATED OVER THE FOUR CORNERS WILL KEEP
TEMPERATURES WELL ABOVE NORMAL AND ALLOW FOR MONSOONAL THUNDERSTORMS
TO DEVELOP OVER THE HIGHER TERRAIN THIS AFTERNOON. PW VALUES ABOVE
1" INDICATE THAT BRIEF, HEAVY RAINFALL WILL BE POSSIBLE WITH ANY
STORM, BUT REALISTIC MAXIMUM RAIN RATES ARE LIKELY CLOSER TO
0.60"/HR OR LESS FOR RIVERSIDE AND SAN DIEGO MOUNTAINS AND 0.40"/HR
OR LESS FOR SAN BERNARDINO THIS AFTERNOON.
SOUNDINGS ARE A BIT MORE OPTIMISTIC FOR STORM POTENTIAL ON
MONDAY/TUESDAY AS THE HIGH BECOMES MORE COMPRESSED BY UPPER LEVEL
TROUGHING OVER THE PACNW, ALLOWING FOR A MORE UNSTABLE ENVIRONMENT
AND MONSOONAL MOISTURE TO SURGE UP INTO THE MOUNTAINS OF SOCAL.
TEMPERATURES WILL ALSO BEGIN TO COOL ON MONDAY AS WE SHED THE LAST
OF OUR HEAT PRODUCTS. WHILE HEATRISK WILL BE LOWER ON MONDAY, HIGHS
WILL STILL BE ABOVE 100 IN THE HIGH DESERTS AND ABOVE 105 IN THE LOW
DESERTS, SO CONTINUE BEST PRACTICES WHEN SPENDING TIME OUTDOORS -
FREQUENT WATER/AC BREAKS AND AVOID STRENUOUS ACTIVITY DURING THE
HOTTEST PARTS OF THE DAY. IF ATTEMPTING TO ESCAPE TO THE MOUNTAINS
TO AVOID THE HEAT, BE PREPARED FOR MORE WIDESPREAD THUNDERSTORMS
MONDAY AFTERNOON WITH HEAVY RAIN, FREQUENT LIGHTNING, AND LOCALIZED
FLOODING POSSIBLE AS INSTABILITY PEAKS ON THIS DAY. WITH EASTERLY
FLOW AND AMPLE MID AND LOW LEVEL MOISTURE, PWS WILL BE INCREASING
CLOSER TO 1.5-1.6, AND RAIN RATES MAY POTENTIALLY EXCEED 1-1.25"/HR
AT TIMES WITH ANY ANCHORED STORM. THE MAJORITY OF THE STORMS ARE
EXPECTED TO REMAIN IN THE MOUNTAINS, BUT A FEW STRONGER CELLS MAY
MAKE IT OFF AND MIGRATE INTO THE DESERTS.
TEMPERATURES WILL COOL FURTHER TUESDAY BACK DOWN TO NEAR NORMAL AS
HEIGHTS CONTINUE TO FALL AND THE MARINE LAYER DEEPENS INTO THE END
OF THE WEEK. ONE FINAL DAY OF SCATTERED MONSOONAL THUNDERSTORMS IN
THE HIGHER TERRAIN AS PWS REMAIN AT OR ABOVE 1.5" AND INSTABILITY
LINGERS ACROSS SOUTHEASTERN CA. AFTER TUESDAY, MORE ROBUST UPPER
LEVEL TROUGHING AND THE HIGH SLIDING FURTHER EASTWARD WILL USHER IN
SLIGHTLY BELOW NORMAL TEMPERATURES INTO THE END OF THE WEEK, ALONG
WITH LOWER STORM CHANCES (10-15% CHANCE FOR A STORM OR TWO OFF THE
HIGHER TERRAIN WILL EXIST EACH AFTERNOON WED-FRI). THIS COOLER
WEATHER WILL BE A WELCOME CHANGE AFTER TEMPERATURES HAVE REMAINED
AT OR ABOVE NORMAL SINCE EARLY JULY.
AVIATION
091800Z....COAST...LOW CLOUDS ARE CONTINUING TO CLEAR ALONG THE
COAST WITH A FEW CLOUDS LINGERING AROUND 1,200-1,500FT MLS. LOW
CLOUDS WITH BASES 1,000-1,500FT MSL WILL START TO REDEVELOP AFTER 03-
05Z MONDAY, INCREASING IN COVERAGE AND MOVING FURTHER INLAND BY 08-
10Z. INTERMITTENT LOWER CIGS 500-800FT MSL ALONG COASTAL SITES 11-
15Z. LOW CLOUDS SCATTER OUT 16-18Z.
VALLEYS/MOUNTAINS/DESERTS...SCT-BKN CUMULUS STILL EXPECTED TO
DEVELOP OVER THE MOUNTAINS THIS AFTERNOON WITH A 20-35% CHANCE OF
TSRA IN THE MOUNTAINS. ANY STORMS THAT MAY DEVELOP COULD PRODUCE
LIGHTNING, UDDFS AND ASSOCIATED VIS REDUCTIONS. MID/HIGH CLOUDS MAY
DRIFT INTO THE VALLEYS AND DESERTS WITH BASES AOA 10,000-15,000 FT
MSL.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH THURSDAY.
BEACHES
ASTRONOMICAL HIGH TIDES ARE EXPECTED TO EXCEED 7 FT MONDAY THROUGH
WEDNESDAY BETWEEN 8-9:30 PM PDT. SURF IS NOT EXPECTED TO PLAY A
LARGE ROLE IN ELEVATING THE TIDES FURTHER, WITH A SURF FORECAST OF
ONLY 2-3 FT. REGARDLESS, TIDES EXCEEDING 7 FT CAN RESULT IN MINOR
TIDAL OVERFLOW INTO LOW-LYING AREAS ALONG THE BEACH, INCLUDING BEACH
PARKING LOTS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...HEAT ADVISORY UNTIL 8 PM PDT THIS EVENING FOR 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.
EXTREME HEAT WARNING UNTIL 8 PM PDT THIS EVENING FOR APPLE AND
LUCERNE VALLEYS-COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS-
SAN GORGONIO PASS NEAR BANNING.
PZ...NONE.
PUBLIC...ZUBER
AVIATION/MARINE/BEACHES...VILLAFANE
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