399
FXUS66 KSGX 042340
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
440 PM PDT TUE AUG 4 2026
SYNOPSIS
INCREASED HEATRISK EXPECTED THROUGH SATURDAY WITH MODERATE HEATRISK
FOR THE MOUNTAINS AND INLAND EMPIRE WITH AREAS OF MAJOR HEATRISK IN
THE DESERTS. AN INFLUX OF MONSOONAL MOISTURE EARLY NEXT WEEK WILL
TAPER DAYTIME HIGHS IN THE DESERTS. ADDITIONALLY THERE IS A 15-20%
CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS IN THE
AFTERNOONS SUNDAY THROUGH TUESDAY, MOST WIDESPREAD CHANCES SUNDAY
AND MONDAY. COASTAL AREAS WILL CONTINUE TO SEE LOW CLOUDS EACH NIGHT
AND MORNING THROUGH THE FORECAST PERIOD.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
..UPDATED AVIATION DISCUSSION
A PERSISTENT AREA OF HIGH PRESSURE WILL REMAIN OVER THE WESTERN
UNITED STATES THROUGH THE WEEKEND. THE POSITION OF THE HIGH THROUGH
WEDNESDAY WILL ALLOW FOR A SHALLOW INFLUX OF MOISTURE INTO THE LOWER
DESERTS, WHICH MAY TAPER DAYTIME HIGHS BUT ELEVATE OVERNIGHT LOWS.
THE HIGH IS EXPECTED TO STRENGTHEN THURSDAY THROUGH SATURDAY,
BRINGING WIDESPREAD MODERATE HEATRISK TO THE INLAND EMPIRE AND
MOUNTAINS AND AREAS OF MAJOR HEATRISK TO THE DESERTS.
HIGH TEMPERATURES THROUGH WEDNESDAY WILL GENERALLY BE WITHIN A FEW
DEGREES OF AVERAGE. THURSDAY THROUGH SATURDAY HIGHS WILL BE ABOVE
AVERAGE NEAR THE COAST TO 5 TO LOCALLY 10 DEGREES ABOVE AVERAGE FOR
SOME INLAND AREAS. LOW TEMPERATURES WILL ALSO RUN ABOVE AVERAGE,
MOST NOTICEABLE IN THE MOUNTAINS AND DESERTS WHERE LOWS WILL BE 10
TO 15 DEGREES ABOVE AVERAGE. FOR THE INLAND EMPIRE AND MOUNTAINS,
THE WIDESPREAD MODERATE HEATRISK INDICATES THAT FOLKS WHO ARE
SENSITIVE HEAT, ESPECIALLY THOSE WITHOUT CONSISTENT
COOLING/HYDRATION, WILL BE MOST IMPACTED. IN THE DESERTS, MAJOR
HEATRISK INDICATES ANYONE MAY SEE NEGATIVE IMPACTS FROM THE HEAT
IF PRECAUTIONS AREN'T TAKEN. MAKE SURE TO STAY HYDRATED AND IF
POSSIBLE AVOID STRENUOUS ACTIVITY DURING THE HOTTEST PARTS OF THE
DAY (10 AM TO 4 PM).
FOR SUNDAY THROUGH TUESDAY, THE HIGH PRESSURE WILL BEGIN TO SLOWLY
WEAKEN WITH THE FLOW ALOFT BECOMING MORE SOUTHEASTERLY. THIS WOULD
ALLOW FOR SOME ADDITIONAL INFLUX OF MONSOONAL MOISTURE INTO THE AREA
AND BRING A 15 TO 20 PERCENT CHANCE OF SHOWERS AND THUNDERSTORMS TO
THE MOUNTAINS EACH AFTERNOON. ENSEMBLE GUIDANCE SHOW PRECIPITABLE
WATER VALUES AND INSTABILITY PEAKING SUNDAY AND MONDAY. CURRENT
FORECAST FOLLOWS THE NBM WHICH HAS CHANCES EACH AFTERNOON, WITH
MOST WIDESPREAD COVERAGE SUNDAY AND MONDAY.
AVIATION
042330Z....COASTS/VALLEYS...PATCHES OF LOW CLOUDS ARE PERSISTING
ALONG THE COAST AROUND 1,800-2,200. LOW CLOUDS AROUND 1000 FEET MSL
WILL REDEVELOP OVER COASTAL AREAS 02-05Z, PUSHING INLAND UP TO 15-20
MILES OVERNIGHT. MINOR VIS REDUCTIONS (3-6SM) POSSIBLE FOR ELEVATED
INLAND VALLEYS WHERE CLOUDS INTERSECT TERRAIN. LOW CLOUDS CLEAR 16-
17Z WITH VFR CONDITIONS THROUGH 00Z.
MOUNTAINS/DESERTS
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD
WITH SCT-BKN HIGH CLOUDS AOA 20,000FT MSL.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH SATURDAY.
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 SATURDAY FOR RIVERSIDE COUNTY
MOUNTAINS-SAN BERNARDINO COUNTY MOUNTAINS-SAN BERNARDINO
AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SAN DIEGO
COUNTY MOUNTAINS.
EXTREME HEAT WARNING UNTIL 8 PM PDT SATURDAY FOR APPLE AND
LUCERNE VALLEYS-COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS-
SAN GORGONIO PASS NEAR BANNING.
PZ...NONE.
PUBLIC...CO
AVIATION/MARINE...VILLAFANE
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