971
FXUS66 KSGX 052020
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
120 PM PDT FRI SEP 5 2025
SYNOPSIS
NEAR NORMAL TEMPERATURES WILL PREVAIL THROUGH THE WEEKEND AS
MONSOONAL MOISTURE SLOWLY LESSENS OVER THE REGION. BY SUNDAY,
THERE WILL BE MINIMAL CHANCES FOR THUNDERSTORMS ACROSS THE
MOUNTAINS INTO NEXT WEEK AS A TROUGH OF LOW PRESSURE MOVES CLOSER
TO THE REGION. THIS SYSTEM WILL BRING A COOLING TREND WITH
BREEZIER WEATHER ACROSS THE MOUNTAINS AND DESERTS WITH A DEEPER
MARINE LAYER WEST OF THE MOUNTAINS.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
CUMULUS CLOUDS CONTINUE TO BUILD ACROSS THE MOUNTAINS WITH AREAS
OF SHOWERS AND WEAK THUNDERSTORMS. ISOLATED STORM ACTIVITY WILL
CONTINUE THROUGH THE LATE AFTERNOON AS RAIN RATES LOCALLY REACH
OVER THREE QUARTERS OF AN INCH. OTHER AREAS ARE SEEING MOSTLY
CLEAR SKIES WITH 80S/90S FOR VALLEYS WEST OF THE MOUNTAINS AND
COMFORTABLE 70S ACROSS THE BIG BEAR LAKE REGION. A STRONGER AREA
OF LOW PRESSURE WILL MOVE CLOSER TO THE WEST COAST THIS WEEKEND,
BRINGING A COOLING AND DRYING INFLUENCE OVER THE REGION. BY
SATURDAY, THIS DRYING EFFECT WILL BE FELT AS MONSOONAL MOISTURE
AND INSTABILITY BEGIN TO LOWER. THIS WILL STILL PROVIDE ENOUGH
FORCING FOR ONE MORE DAY OF A SIGNIFICANT CHANCE OF STORMS,
PRIMARILY ACROSS THE RIVERSIDE/SAN DIEGO CO MOUNTAINS. STORMS WILL
BE WEAKER AND MORE ISOLATED IN NATURE.
AREAS WEST OF THE MOUNTAINS WILL SEE A FAIRLY UNCHANGED WEATHER
PATTERN THROUGH THE WEEKEND WITH HIGH TEMPERATURES SIMILAR TO
THOSE OF TODAY. EVERYONE ACROSS SOCAL WILL ALSO START TO FEEL
LESSER AMOUNTS OF HUMIDITY AS GET INTO THE WEEKEND AS WELL. THIS
IS ALL THANKS TO AN AREA OF LOW PRESSURE THAT WILL MOVE ACROSS THE
STATE BY EARLY NEXT WEEK. AS IT DOES SO, WE CAN EXPECT
TEMPERATURES TO COOL THROUGH THE MIDDLE OF THE WEEK WITH HIGHS 5
TO 15 DEGREES BELOW AVERAGE. THERE IS HIGH CONFIDENCE IN FORECAST
HIGH TEMPERATURES BY WEDNESDAY WILL BE IN THE 70S/80S FOR MANY
WEST OF THE MOUNTAINS INTO THE HIGH DESERT WITH 90S IN THE LOWER
DESERTS. ENSEMBLE MODEL GUIDANCE IS IN GOOD AGREEMENT OF THIS
TROUGH STICKING AROUND INTO LATER IN THE WEEK, WHICH WOULD
CONTINUE THE COOLER AND DRIER WEATHER PATTERN.
AVIATION
052000Z...COAST...LOW CLOUDS BASED AROUND 900-1500 FT MSL HAVE
REMAINED OVER THE INNER WATERS AND RIGHT ALONG THE COASTAL AREAS
THROUGH THIS AFTERNOON, WITH SKIES OCCASIONALLY GOING BKN-OVC FOR
SOME OF THE COASTAL SITES. CLOUDS WILL CONTINUE TO FILL IN THIS
EVENING AFTER 06Z SAT, WITH SIMILAR BASES, BUT LESS INLAND EXTENT.
CLOUDS WILL BEGIN TO ERODE FROM EAST TO WEST BEGINNING AROUND 14Z
AND THEN CLEARING TOWARDS THE COAST BY 16-17Z SAT.
VALLEYS/MOUNTAINS/DESERTS...ISOLATED SHRA/TSRA EXPECTED OVER SAN
DIEGO COUNTY AND SOUTHERN RIVERSIDE COUNTY MOUNTAINS AGAIN THIS
THROUGH 01Z THIS EVENING, WITH SLIGHTER CHANCES (15-20%) FOR MORE
NORTHERLY MTNS AND DESERTS/DESERT FOOTHILLS. CB BASES OF ABOUT 10000
FEET MSL WITH TSRA TOPS TO 35K FEET. GUSTY, ERRATIC WINDS, BLOWING
DUST WITH LOW VISIBILITY, LIGHTNING, AND LOWER BASES 6000-9000 FEET
MSL WILL OCCUR WITH ANY TSRA. THERE WILL BE EVEN A LESSER CHANCE OF
SHRA/TSRA TOMORROW AFTERNOON AFTER 19Z, AND LIKELY VERY ISOLATED,
WITH THE BEST CHANCE BEING OVER THE SOUTHERN MOUNTAINS OF SAN DIEGO
COUNTY.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH TUESDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
PUBLIC...APR
AVIATION/MARINE...STEWEY
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