994
FXUS66 KSGX 220406
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
906 PM PDT MON APR 21 2025
SYNOPSIS
NIGHT AND MORNING LOW CLOUDS ARE EXPECTED EACH DAY AT THE COAST
EARLY THIS WEEK, BECOMING MORE WIDESPREAD INTO THE VALLEYS FOR THE
MIDDLE TO END OF THE WEEK. INCREASED SEA BREEZE WINDS ARE EXPECTED
EACH AFTERNOON AND EVENING FOR THE MOUNTAINS AND DESERTS. A COOLING
TREND WILL START TODAY WEST OF THE MOUNTAINS. FOR THE MOUNTAINS AND
DESERTS A FEW DEGREES OF WARMING EXPECTED EARLY IN THE WEEK, BEFORE
A COOLING TREND FOR THE MIDDLE TO END OF THE WEEK. GRADUAL
WARMING IS EXPECTED EARLY NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS EVENING...SFC PRESSURE GRADIENTS ARE TRENDING STRONGER
ONSHORE AND CURRENTLY SUPPORTING WIND GUSTS OF 20-30 MPH IN THE
MTN PASSES AND ON ADJACENT DESERT SLOPES. WINDS WILL CONTINUE TO
WEAKEN OVERNIGHT THEN STRENGTHEN TOMORROW AFTERNOON WITH THE
DIURNAL CYCLE. THE MARINE LAYER HAS DEEPENED TO ABOUT 1700 FT AND
LOW CLOUDS ARE INCREASING IN COVERAGE AS THEY SPREAD FARTHER
INLAND. LOW CLOUDS COULD REACH UP TO 20 MILES INLAND BY SUNRISE ON
TUESDAY.
FROM PREVIOUS DISCUSSION...
A SERIES OF PASSING TROUGHS THIS WEEK WILL MAINTAIN ONSHORE FLOW
ACROSS THE REGION. THIS WILL CAUSE THE MARINE LAYER TO DEEPEN
THROUGH THE WEEK REACHING THE WESTERN VALLEYS BY TOMORROW AND
FILLING IN MUCH OF THE COASTAL BASIN BY WEDNESDAY. IN ADDITION,
ELEVATED SEA BREEZE WINDS CAN BE EXPECTED MOST AFTERNOONS AND
EVENINGS FOR THE MOUNTAINS, DESERTS, AND PASSES.
A COOLING TREND FOR THE COAST AND VALLEYS WILL CONTINUE THROUGH
SATURDAY. THE MOUNTAINS AND DESERTS WILL WARM A FEW DEGREES
TOMORROW, BEFORE A COOLING TREND SETS IN THROUGH SATURDAY. FOR EARLY
NEXT WEEK, HIGH PRESSURE WILL BEGIN TO STRENGTHEN OFF THE WEST COAST
WITH WARMING FOR SOUTHERN CALIFORNIA.
THERE REMAINS UNCERTAINTY IN THE UPPER LEVEL PATTERN FOR FRIDAY
THROUGH THE WEEKEND. WHILE THERE IS HIGH CONFIDENCE THE PATTERN WILL
CONTINUE TO BE DOMINATED BY LOW PRESSURE TROUGHING THROUGH AT
LEAST SATURDAY, THERE ARE MULTIPLE ENSEMBLE SOLUTIONS REGARDING
THE PLACEMENT OF THE PASSING TROUGH. SOLUTIONS WITH MORE INFLUENCE
FROM THE ECMWF SHOW THE TROUGH DIGGING FURTHER SOUTH WHICH WOULD
RESULT IN COOLER AND WINDIER CONDITIONS FOR SOUTHERN CALIFORNIA
WITH THE POTENTIAL FOR MARINE LAYER DRIZZLE. SOLUTIONS THAT HAVE
MORE INFLUENCE FROM THE CANADIAN AND GFS KEEP THE LOW FURTHER
NORTH, WHICH WOULD RESULT IN LESS INFLUENCE ON THE WEATHER IN
SOUTHERN CALIFORNIA OVERALL. NBM CHANCES FOR WIND GUSTS EXCEEDING
40 MPH SATURDAY EVENING ARE 15 TO 25 PERCENT FOR THE DESERTS, WITH
CHANCES INCREASING TO 60 TO 70 PERCENT THROUGH THE PASSES AND
LOCALLY ON DESERT MOUNTAIN SLOPES.
AVIATION
220300Z....COASTS/VALLEYS...LOW CLOUDS BASED 1100-1600 FT MSL WITH
TOPS TO 2000 FT MSL HAVE MOVED INTO PARTS OF THE COAST, AND WILL
CONTINUE TO PUSH ASHORE AND NORTHWARDS THROUGH EARLY TUESDAY MORNING
TO FILL MUCH OF THE COASTAL BASIN. 60% CHANCE FOR IMPACTS AT KONT BY
12Z, WITH LOWER CHANCES (AROUND 30%) AT KSBD. VIS REDUCED 1-5 SM
INLAND AND ON HIGHER COASTAL TERRAIN. SCATTER OUT FROM EAST TO WEST
16-18Z TUES. LOW CLOUDS AT 1500-2000 FT MSL WILL REFORM AND PUSH
INLAND AGAIN AFTER 02Z WED TO AGAIN COVER MUCH OF THE COASTAL BASIN.
OTHERWISE...MOSTLY CLEAR TONIGHT THROUGH TUESDAY MORNING, WITH
FEW-SCT HIGH CLOUDS TUES AFTERNOON AND EVENING.
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...NONE.
PZ...NONE.
PUBLIC...PG
AVIATION/MARINE...CSP
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