854
FXUS66 KSGX 160408
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
908 PM PDT THU MAY 15 2025
SYNOPSIS
LITTLE CHANGE IN TEMPERATURES FRIDAY. COOLER, CLOUDIER, AND
WINDIER WITH CHANCES OF PRECIPITATION ALONG AND WEST OF THE
MOUNTAINS OVER THE WEEKEND. MUCH WARMER WITH A SHALLOWER MARINE
LAYER EXPECTED NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
LOW CLOUDS HAVE REDEVELOPED ALONG THE SAN DIEGO COUNTY COAST THIS
EVENING, WHILE ELSEWHERE SKIES REMAIN CLEAR. THE 00Z KNKX SOUNDING
SHOWS THE MARINE INVERSION BASED NEAR 2300 FT MSL, LITTLE CHANGE
FROM THIS MORNING. A WEAK COASTAL EDDY DEVELOPS TONIGHT, WHICH MAY
RESULT IN A SLIGHT INCREASE IN THE MARINE LAYER DEPTH, WITH LOW
CLOUDS EXTENDING INTO THE FAR SOUTHERN AND WESTERN PORTIONS OF THE
INLAND EMPIRE BY FRIDAY MORNING. WEAK TROUGHING REMAINS OVER THE
REGION ON FRIDAY WITH GENERALLY LITTLE CHANGES IN HIGH
TEMPERATURES FROM TODAY.
ANOTHER UPPER TROUGH APPROACHES THE WEST COAST BY LATE FRIDAY AND
DIGS THROUGH INTERIOR CALIFORNIA AND NEVADA ON SATURDAY, FOLLOWED
BY A SECOND UPPER LOW MOVING FROM THE PAC NW INTO THE GREAT BASIN
ON SUNDAY. THIS WILL GENERATE GUSTY WEST WINDS ACROSS THE
MOUNTAINS, DESERTS, AND COASTAL WATERS THIS WEEKEND. CURRENTLY
PEAK WIND GUSTS ARE FORECAST TO BE AROUND 40-50 MPH, THOUGH
ISOLATED GUSTS OF 60 MPH ORE MORE ARE LIKELY (70-80% CHANCE)
THROUGH THE FAVORED PASSES SATURDAY AFTERNOON AND EVENING. THIS
TROUGH WILL ALSO BRING CONSIDERABLE COOLING WITH HIGHS FALLING TO
10-15 DEGREES BELOW NORMAL INLAND ON SATURDAY. WITH THE TROUGH
AXIS PASSAGE LATE SATURDAY AND A DEEP MARINE LAYER IN PLACE, AREAS
OF DRIZZLE OR LIGHT SHOWERS ARE POSSIBLE ALONG AND WEST OF THE
MOUNTAINS, WITH THE GREATEST CHANCES IN SAN DIEGO COUNTY DUE TO
THE MORE NORTHWESTERLY FLOW. CHANCES OF ACCUMULATING PRECIPITATION
RANGE FROM AROUND 10% ALONG THE LA COUNTY BORDER TO AROUND 20%
ALONG THE FOOTHILLS OF THE MOUNTAINS, INCREASING TO AROUND 30-40%
ACROSS SAN DIEGO COUNTY FROM THE COASTAL SLOPES WESTWARD. CHANCES
OF 0.10" OR MORE ARE AROUND 10-25% IN SAN DIEGO COUNTY, HIGHEST
ALONG THE COASTAL MOUNTAIN SLOPES, AND LESS THAN 10% FOR AREAS
NORTHWARD. BASED ON CURRENT TIMING OF THE TROUGH, MOST OF THIS
PRECIPITATION IS EXPECTED TO FALL SATURDAY EVENING INTO SATURDAY
NIGHT. THERE COULD BE SOME DRIZZLE SATURDAY MORNING AS WELL,
THOUGH THE CHANCES OF ANY ACCUMULATING PRECIPITATION IS LESS THAN
10%. HEIGHT RISES ON SUNDAY AS THE FIRST WAVE MOVES OUT SHOULD
ALLOW FOR SOME WARMING THOUGH HIGHS WILL STILL BE AROUND 7-12
DEGREES BELOW NORMAL. BREEZY ONSHORE WINDS WILL CONTINUE INTO
SUNDAY EVENING, WEAKENING INTO MONDAY AS ONSHORE PRESSURE
GRADIENTS RELAX AND FLOW ALOFT WEAKENS.
THE TROUGH WILL BE REPLACED BY WEAK UPPER RIDGING EARLY IN THE
WEEK, BRINGING WARMER WEATHER WITH LESS MARINE LAYER CLOUD COVER.
AROUND 27% OF THE ENSEMBLES HAVE THE FINAL SHORT WAVE TRACKING FAR
ENOUGH WEST ACROSS THE GREAT BASIN TO GENERATE WEAK OFFSHORE FLOW
IN SO CAL TUESDAY MORNING, THOUGH THE REMAINING MEMBERS KEEP THE
WAVE MUCH FURTHER INSIDE WITH A CONTINUATION OF ONSHORE FLOW. IF
THE OFFSHORE FLOW WERE TO OCCUR, IT WOULD RESULT IN WARMER AND
DRIER CONDITIONS WEST OF THE MOUNTAINS ON TUESDAY. GENERALLY
CONSENSUS IS FOR WEAK RIDGING TO CONTINUE THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK FOR CONTINUED WARMING, THOUGH A SMALL NUMBER
OF MEMBERS (AROUND 15-25% OF THEM) TRY TO DEVELOP SOME WEAK
TROUGHING ALONG THE PAC NW INTO CENTRAL CA WED AND THU, WHICH
WOULD LIMIT WARMING. FOR WEDNESDAY AND THURSDAY, THERE IS A 80-95%
CHANCE OF HIGHS OF 90 DEGREES OR MORE IN THE INLAND VALLEYS AND
HIGH DESERTS, AND A 90-100% CHANCE OF HIGHS OF 1100 OR MORE IN THE
LOW DESERTS. THE GOOD NEWS IS THE CHANCE OF HIGHS OF 110 OR MORE
ARE LESS THAN 10%.
AVIATION
160335Z...COAST/VALLEYS...LOW CLOUDS BASED 1200-1500 FT MSL HAVE
DEVELOPED ALONG THE SAN DIEGO COUNTY COAST AND WILL CONTINUE TO
EXPAND NORTHWARDS THIS EVENING AND THEN 20-25 MILES INLAND
OVERNIGHT, WITH THE POTENTIAL TO REACH PORTIONS OF THE INLAND EMPIRE
BY 08Z FRI. THERE IS A 60% CHANCE OF LOW CLOUDS REACHING KONT BY 12Z
FRI. LOW CLOUDS EXPECTED TO CLEAR FROM THE VALLEYS 16-18Z FRI, WITH
MOST COASTAL AREAS SCATTERING OUT 17-20Z WITH THE POTENTIAL FOR
PATCHY CLOUDS TO LINGER ALONG THE IMMEDIATE COAST. LOW CLOUDS WITH
SLIGHTLY HIGHER BASES 1500-2000 FT MSL WILL BECOME MORE WIDESPREAD
AGAIN AFTER 00Z SAT.
MOUNTAINS/DESERTS...MOSTLY CLEAR SKIES TONIGHT, WITH INCREASING
HIGH CLOUDS COVER FRIDAY AOA 20000 FT.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH SATURDAY
MORNING. STRONGER WINDS AND HIGHER SEAS ARE EXPECTED LATE SATURDAY
INTO SUNDAY. WESTERLY WINDS 15 TO 20 KT GUSTING 20 TO 25 KT WITH
WIND-DRIVEN WAVES 6 TO 8 FEET FOR OUTER COASTAL WATERS, WITH WIND
GUSTS 20 KT OR LESS AND WIND-DRIVEN WAVES UP TO 6 FEET EXPECTED FOR
INNER COASTAL WATERS. HAZARDOUS BOATING CONDITIONS FOR SMALL CRAFT
LOOK LIKELY FOR THE OUTER COASTAL WATERS. WINDS AND WAVES GRADUALLY
SUBSIDE MONDAY.
BEACHES
ELEVATED SURF WILL IMPACT BEACHES LATE SUNDAY INTO MONDAY. SURF
HEIGHTS OF 4-6 FEET WITH LOCAL SETS TO 7 FEET ARE POSSIBLE ALONG
WEST-FACING BEACHES. INCREASED SURF WILL RESULT IN AN INCREASED RISK
OF STRONG RIP CURRENTS.
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...SS
AVIATION/MARINE/BEACHES...CSP
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