903
FXUS66 KSGX 280346
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
846 PM PDT WED OCT 27 2021
SYNOPSIS
DRY CONDITIONS AND WARMING EXPECTED THROUGH THURSDAY. COOLING TREND
EXPECTED FRIDAY THROUGH EARLY NEXT WEEK. WEAK SANTA ANA WINDS
THROUGH THURSDAY, WITH GUSTY NORTH TO NORTHEAST WINDS ON COASTAL
MOUNTAIN SLOPES AND BELOW PASSES AND CANYONS. NIGHT AND MORNING LOW
CLOUDS AND FOG COULD BEGIN TO MAKE THEIR RETURN AS EARLY AS FRIDAY
MORNING, DEEPENING FURTHER INTO THE VALLEYS EACH MORNING, REACHING
THE COASTAL MOUNTAIN SLOPES BY SUNDAY AND MONDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
UPDATE:
THE SKY IS CLEAR ACROSS THE REGION. SANTA ANA WINDS ARE BLOWING
WEAKLY THROUGH THE PASSES AND ALONG THE COASTAL MOUNTAIN SLOPES
WITH MOST GUSTS THIS EVENING NEAR 20 MPH. THE EXCEPTION IS WINDY
TORO PEAK AT 40 MPH. SANTA ANA WINDS WILL INCREASE AND PEAK
THURSDAY MORNING WITH GUSTS BELOW PASSES AT 30-40 MPH WITH
LOCALIZED HIGHER GUSTS. IT WILL GET EVEN WARMER ON THURSDAY TOO,
SOME 5-10 DEGREES WARMER THAN TODAY.
PREVIOUS DISCUSSION:
KEY POINTS:
*WEAK SANTA ANA WINDS AND WARM CONDITIONS THROUGH THURSDAY.
*COOLER FRIDAY THROUGH EARLY NEXT WEEK.
TEMPERATURES AT 1 PM TODAY WERE 10 TO 20 DEGREES WARMER THAN 1 PM
YESTERDAY WEST OF THE MOUNTAINS, AND 5 TO 10 DEGREES WARMER THAN
YESTERDAY IN THE DESERTS. EVEN WARMER CONDITIONS ARE EXPECTED
THURSDAY AS HIGH PRESSURE AND WEAK SANTA ANA WINDS CONTINUE TO
IMPACT SOUTHERN CALIFORNIA. HIGH TEMPERATURES WILL BE AROUND 10
DEGREES ABOVE THE SEASONAL AVERAGE WEST OF THE MOUNTAINS. THAT PUTS
HIGHS IN THE LOW 90S IN MOST VALLEY LOCATIONS AND IN THE LOW TO MID
80S NEAR THE COAST. SANTA ANA WINDS WILL CONTINUE INTO TOMORROW
MORNING. NORTH TO NORTHEAST WINDS WITH PEAK GUSTS 30-40 MPH, LOCALLY
45 MPH, EXPECTED ON COASTAL MOUNTAIN SLOPES AND BELOW PASSES AND
CANYONS. 25-30 MPH WIND GUSTS COULD PERIODICALLY REACH NORTHERN
PORTIONS OF THE INLAND EMPIRE, ESPECIALLY BELOW THE CAJON PASS.
THE LATEST LOCAL WRF RUN CONTINUES TO SHOW A WEAK COASTAL EDDY
DEVELOPING LATE THURSDAY NIGHT INTO FRIDAY MORNING. THIS WOULD HELP
PATCHY LOW CLOUDS AND DENSE FOG FORM OVER THE COASTAL WATERS AND
ADJACENT LAND AREAS EARLY FRIDAY MORNING. COASTAL LOW CLOUDS AND FOG
ARE MORE LIKELY TO DEVELOP FRIDAY NIGHT INTO SATURDAY WITH A WELL-
DEVELOPED COASTAL EDDY. THE LOW CLOUDS COULD REACH SOME OF THE
WESTERN VALLEYS SATURDAY MORNING. MORE SUBSTANTIAL DEEPENING IS
EXPECTED INTO SUNDAY MORNING WITH LOW CLOUDS REACHING THE LOWER
COASTAL MOUNTAIN SLOPES.
A SHORT WAVE WILL START TO MOVE INTO SOUTHERN CALIFORNIA THURSDAY,
PUSHING THE RIDGING CURRENTLY OVER THE AREA EAST, AND SPARKING A
COOLING TREND THROUGH EARLY NEXT WEEK. HIGH TEMPERATURES ON SUNDAY
ARE FORECAST TO BE 5 TO 10 DEGREES BELOW AVERAGE FOR THE COAST AND
VALLEYS AND A FEW DEGREES BELOW AVERAGE FOR THE DESERTS WITH HIGHS
MOSTLY IN THE MID 60S TO LOWER 70S FOR THE COAST AND VALLEYS.
ENSEMBLE GUIDANCE GENERALLY SHOWS A SLOW WARMING TREND MONDAY
THROUGH THE MIDDLE OF NEXT WEEK. THE GREATEST SPREAD IN THE HIGH
TEMPERATURE GUIDANCE IS IN THE VALLEYS WITH MODEL DIFFERENCES IN
MARINE LAYER DEPTH AND POSSIBLE WEAK OFFSHORE FLOW.
AVIATION
280300Z...CLEAR WITH UNRESTRICTED VISIBILITY TONIGHT AND THURSDAY.
FROM 06Z-18Z THURSDAY...NORTH/EAST WINDS 20-35 KNOTS IN AND BELOW
THE CAJON PASS WITH AREAS OF LLWS NEAR KONT, KSBD AND KRAL.
MARINE
PATCHY DENSE FOG WITH REDUCED VISIBILITIES OVER THE COASTAL WATERS
LATE THURSDAY NIGHT THROUGH EARLY FRIDAY MORNING. MORE WIDESPREAD
FOG FRIDAY NIGHT/SATURDAY MORNING.
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...GREGORIA (UPDATE)/CO (PREVIOUS DISCUSSION)
AVIATION/MARINE...MOEDE
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