680
FXUS66 KSGX 210436
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
936 PM PDT FRI JUN 20 2025
SYNOPSIS
GUSTY WESTERLY WINDS OVER THE MOUNTAINS AND INTO THE DESERTS THROUGH
SATURDAY WITH COOLER CONDITIONS AND A MORE EXTENSIVE MARINE LAYER
LOW CLOUD COVERAGE. WEAK OFFSHORE FLOW SUNDAY WILL BRING
TEMPERATURES UP A FEW DEGREES. BELOW AVERAGE TEMPERATURES WILL
CONTINUE EARLY IN THE WEEK, WITH A GRADUAL WARMING FOR THE MIDDLE TO
END OF THE WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
UPDATE: THERE HAS BEEN VERY LITTLE CHANGE TO THE FORECAST SINCE THIS
MORNING. MODELS CONTINUE TO SHOW THE TROUGH SLOWLY TRANSITIONING
OVER THE REGION THIS WEEKEND, WITH TEMPERATURES BEING MUCH COOLER,
ESPECIALLY TOMORROW, AND A RETURN OF A MORE PERSISTENT MARINE LAYER.
WINDS HAVE ALSO PICKED UP FOR THE HIGH DESERTS AND WITHIN THE SAN
GORGONIO PASS, WHERE A RAWS SITE NEAR WHITEWATER HILL PICKED UP A
MAX WIND GUST OF 60 MPH WITHIN THE PAST HOUR. THESE WINDS SHOULD
CONTINUE TO BLOW QUITE STRONG THROUGH THE EVENING HOURS TOMORROW,
BUT SHOULD DECOUPLE AND COME DOWN BY AROUND MIDNIGHT TOMORROW, OR
SHORTLY THEREAFTER INTO VERY EARLY SUNDAY MORNING. THIS IS A VERY
DRY LOW PRESSURE SYSTEM, SO OTHER THAN SOME POSSIBLE DRIZZLE FOR
SOME OF THE COASTAL AND INLAND AREAS ON SATURDAY NIGHT THROUGH
SUNDAY MORNING, IT WILL REMAIN DRY.
BEYOND THIS WEEKEND, MODELS STILL INDICATE THAT THERE WILL BE
GENERALLY A BROAD LONGWAVE TROUGH REMAINING IN PLACE OVER THE REGION
DURING THE FIRST HALF OF THE WORK WEEK. THIS WILL BECOME MORE ZONAL,
WITH EVEN SOME SLIGHT RIDGING OVERHEAD TOWARDS THE END OF NEXT WEEK,
WHICH WILL RESULT IN A GRADUAL WARMUP THROUGH THEN.
(PREVIOUS DISCUSSION SUBMITTED AT 126 PM):
FOR THE WEEKEND, AN UPPER LEVEL LOW OFF THE COAST OF BRITISH
COLUMBIA WILL DIG SOUTHEAST INTO THE GREAT BASIN. THIS WILL BRING 5
TO 15 DEGREE BELOW AVERAGE TEMPERATURES FROM THE COAST TO THE
DESERTS SATURDAY. IN ADDITION, GUSTY WESTERLY WINDS CAN BE EXPECTED
OVER THE MOUNTAINS AND INTO THE DESERTS THIS AFTERNOON AND EVENING
AND AGAIN SATURDAY AFTERNOON AND EVENING. WINDS WILL BE STRONGEST
THROUGH THE SAN GORGONIO PASS WHERE GUSTS 55 TO 60 MPH ARE POSSIBLE,
OTHERWISE GUSTS WILL BE 40 TO 50 MPH.
MARINE LAYER LOW CLOUDS AND AREAS OF FOG WILL BE PERSISTENT INTO
NEXT WEEK, WITH VARYING DEPTH. THE MARINE LAYER IS EXPECTED TO
DEEPEN SLIGHTLY SATURDAY, ALTHOUGH THE AMOUNT OF DEEPENING WILL
DEPEND ON THE POSITION OF A POTENTIAL EDDY. AS THE UPPER LEVEL LOW
DIGS INTO THE GREAT BASIN SUNDAY, THE PRESSURE GRADIENT WILL BRIEFLY
TURN OFFSHORE BRINGING AN UPTICK IN NORTHEASTERLY WINDS SUNDAY
MORNING. THOSE OFFSHORE WINDS LOOK TO STAY ON THE WEAKER SIDE, BUT
HAVE THE POTENTIAL TO INHIBIT LOW CLOUDS REACHING PORTIONS OF THE
INLAND EMPIRE AND NEAR MOUNTAIN FOOTHILLS.
A SECONDARY LOW WILL DEVELOP IN THE MEAN TROUGH SUNDAY NIGHT INTO
MONDAY AND DIGS TOWARDS SOUTHERN CALIFORNIA BEFORE PROGRESSING
WESTWARD ON TUESDAY. THIS WILL MAINTAIN COOLER WEATHER WITH HIGHS 5
TO 10 DEGREES BELOW NORMAL THROUGH TUESDAY AND MARINE LAYER LOW
CLOUDS SPREADING INTO THE WESTERN VALLEYS EACH NIGHT. FOR WEDNESDAY
THROUGH THE END OF NEXT WEEK, THE UPPER LEVEL TROUGHING SHIFTS NORTH
RESULTING IN A GRADUAL WARMING AND LESS EXTENSIVE NIGHT AND MORNING
LOW CLOUDS. CURRENT FORECAST FOR THE END OF THE WEEK FOLLOWS NBM
WITH HIGHS WITHIN A FEW DEGREES OF NORMAL.
AVIATION
210435Z....COAST/VALLEYS...LOW CLOUDS HAVE SPREAD LOCALLY UP TO 20
MILES INLAND AT THIS HOUR, WITH BASES 1600-2000 FEET MSL AND TOPS TO
3000 FEET. LOW CLOUDS SHOULD FILL THE COASTAL BASIN BY 13Z. THERE IS
HIGH CONFIDENCE FOR CIG IMPACTS UNTIL ABOUT 17Z AT ALL TAF SITES
WEST OF THE MTNS EXCEPT KSBD WHICH SHOWS ABOUT A 45 PERCENT CHANCE
FOR CIG IMPACTS 10Z-13Z. VIS 1-5SM WHERE CLOUDS AND TERRAIN
INTERSECT, OBSCURING HIGHER TERRAIN. CLEARING TO THE COAST EXPECTED
17-20Z.
MOUNTAINS/DESERTS
CLEAR SKIES AND UNRESTRICTED VIS THROUGH
SATURDAY. WESTERLY WINDS WITH GUSTS 25-45 KNOTS THROUGH MOUNTAIN
PASSES AND LOCALLY INTO DESERTS, LIKELY PRODUCING POCKETS OF
UP/DOWNDRAFTS IN LEE OF MOUNTAINS/MOUNTAIN PASSES IN ADDITION TO
ISOLD BLDU IN THE DESERT WITH VIS 3-5SM AT TIMES. A SLIGHT WEAKENING
SATURDAY MORNING. THE STRONG WESTERLY WINDS LIKELY TO RETURN
SATURDAY AFTERNOON AND EVENING.
MARINE
NORTHWEST WIND GUSTS 20-25 KNOTS NEAR SAN CLEMENTE ISLAND THIS
EVENING, WEAKENING OVERNIGHT THEN RETURNING SATURDAY
AFTERNOON/EVENING. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE
EXPECTED THROUGH NEXT WEDNESDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...WIND ADVISORY UNTIL 11 PM PDT SATURDAY FOR APPLE AND LUCERNE
VALLEYS-SAN DIEGO COUNTY DESERTS-SAN GORGONIO PASS NEAR
BANNING.
PZ...NONE.
UPDATE...STEWEY
PUBLIC...CO
AVIATION/MARINE...PG
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