359
FXUS66 KSGX 091804
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
1104 AM PDT SUN AUG 9 2026
SYNOPSIS
MINOR TO MAJOR HEATRISK CONTINUES FOR MUCH OF THE REGION THROUGH
TODAY BEFORE COOLER WEATHER RETURNS FOR TUESDAY AND BEYOND.
THUNDERSTORM CHANCES CONTINUE EACH AFTERNOON AND EVENING IN THE
MOUNTAINS AND DESERTS THROUGH WEDNESDAY, WITH BEST CHANCES AND
HIGHEST RAIN RATES MONDAY AND TUESDAY. PATCHY COASTAL LOW CLOUDS
AND FOG THIS MORNING FOLLOWED BY A DEEPENING MARINE LAYER AFTER
MONDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
..UPDATED AVIATION DISCUSSION
THIS MORNING...OUTFLOW FROM A COLLAPSED MCS (MESOSCALE CONVECTIVE
SYSTEM) OVER WESTERN AZ IS MOVING WESTWARD ACROSS RIVERSIDE COUNTY
AND PRODUCING ISOLATED, WEAK TSTMS. THESE STORMS WILL LIKELY
COLLAPSE BEFORE REACHING WESTERN RIVERSIDE OR SAN BERNARDINO
COUNTIES BUT THERE IS A SMALL CHANCE THAT THEY COULD REACH THE
COACHELLA VALLEY INTACT BY 3 AM. IF ANY STORMS REACH WESTERN
RIVERSIDE COUNTY, THEY WILL LIKELY BE QUITE WEAK. ALTHOUGH LOCALLY
GUSTY WINDS COULD STILL BE PRODUCED. THE MARINE LAYER REMAINS
QUITE SHALLOW AND LOW CLOUDS ARE SLOW TO DEVELOP. LOW CLOUD
DEVELOPMENT COULD BE FURTHER DISRUPTED AS THE OUTFLOW FROM THE MCS
OVER AZ MOVES WEST OF THE MTNS, ALTHOUGH THE OUTFLOW WILL BE MUCH
WEAKENED AS IT MOVES WESTWARD.
THE HIGH PRESSURE OVER THE SOUTHWEST WILL CONTINUE TO DOMINATE OUR
WEATHER THROUGH TUESDAY EVEN AS IT WEAKENS IN RESPONSE TO A SERIES
OF SHORTWAVE TROUGHS MOVING INLAND TO THE NORTH. THE POSITION OF
THE HIGH WILL ALLOW THE MONSOONAL FLOW TO CONTINUE BRINGING DEEP-
LAYER MOISTURE INTO SOCAL FROM THE SOUTHEAST. THIS WILL CONTINUE
TO SUPPORT THE POTENTIAL FOR AFTERNOON/EVENING SHOWERS AND TSTMS,
MAINLY IN THE MTNS AND DESERTS. DAYTIME HIGH TEMPERATURES WILL
GRADUALLY LOWER THROUGH THE WEEK BUT REMAIN ABOVE NORMAL THROUGH
MONDAY. TODAY, WE WILL STILL HAVE MINOR HEATRISK IN THE INLAND
VALLEYS AND MTNS, AND MAJOR HEATRISK IN THE DESERTS. BY TUESDAY,
DAYTIME HIGH TEMPERATURES WILL BE NEAR OR A FEW DEGREES BELOW
NORMAL. THE MARINE LAYER WILL GRADUALLY DEEPEN AS THE HIGH ALOFT
WEAKENS.
FOR WED THROUGH NEXT WEEKEND (ACCORDING TO MODEL CONSENSUS)...A
TROUGH OF LOW PRESSURE DEEPENS ALONG THE COAST. THIS WILL BRING
MORE PRONOUNCED COOLING, WITH DAYTIME HIGH TEMPERATURES AS MUCH AS
10 DEGREES BELOW NORMAL IN SOME INLAND AREAS BY THURSDAY. THE
BELOW-NORMAL TEMPERATURES WILL CONTINUE INTO NEXT WEEKEND. THE
TROUGH WILL ALSO BRING DRY, SOUTHWEST FLOW ALOFT, REDUCING THE
POTENTIAL FOR PM SHOWERS/TSTMS BY WED AND ESSENTIALLY ELIMINATING
IT FOR THURSDAY THROUGH NEXT WEEKEND. IN ADDITION, THE MARINE
LAYER WILL DEEPEN AND LOW CLOUDS AND FOG COULD SPREAD INLAND TO
THE COASTAL SLOPES DURING THE NIGHTS AND MORNINGS.
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.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
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...PG
AVIATION/MARINE/BEACHES...VILLAFANE
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