874
FXUS66 KSGX 180421
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
921 PM PDT FRI OCT 17 2025
SYNOPSIS
DRIER AND WARMER WEATHER WITH WEAK OFFSHORE FLOW AND HIGH
PRESSURE BUILDING IN, ALLOWING TEMPERATURES TO RISE TO NEAR NORMAL
INTO THE WEEKEND. SLIGHTLY COOLER FOR EARLY NEXT WEEK AS AN UPPER
LEVEL LOW MOVES INLAND, DECREASING HEIGHTS. THE LOW WILL BRING
FURTHER COOLING FOR THE END OF THE NEXT WEEK AND A LOW CHANCE OF
SHOWERS, WITH CHANCES FOR MEASURABLE RAINFALL CURRENTLY LESS THAN
10%.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
UPDATE: THE NEGATIVELY TILTED TROUGH LOCATED OVER THE FOUR
CORNERS REGION IS CONTINUING TO PROPAGATE EASTWARD WITH HIGH
PRESSURE CONDITIONS SETTING IN BEHIND IT. SKIES CONTINUE TO REMAIN
CLEAR ACROSS THE REGION THIS EVENING WITH WEAK OFFSHORE WINDS.
SOME LOW CLOUDS MAY EVENTUALLY BEGIN TO DEVELOP OVER THE INNER
COASTAL WATERS, AND THEN MOVE IN ALONG PORTIONS OF THE COASTLINE,
AND ALSO POSSIBLE WITHIN SOME OF THE INLAND VALLEYS, OTHERWISE
SKIES SHOULD REMAIN CLEAR FOR MOST AREAS. THERE MAY ALSO BE SOME
PATCHY AREAS OF FOG DEVELOPING WITHIN SOME OF THE WIND-SHELTERED
VALLEYS, ESPECIALLY TOWARDS THE EARLY MORNING HOURS AND CLOSER TO
THE TIME OF MAX COOLING. LOWS OVERNIGHT WILL FALL INTO THE 40S
AGAIN FOR MOST OF THE INLAND AREAS AND WITHIN THE IE, BUT PERHAPS
A SMIDGEN WARMER THAN LAST NIGHT. THE OVERALL FORECAST FOR THE
NEXT WEEK HASN'T CHANGED TOO MUCH, OTHER THAT THE TREND HAS BEEN
GOING DRIER IN TERMS OF THE UPPER LEVEL LOW THAT CUTS OFF FROM THE
ELONGATED TROUGH OVER THE PACIFIC, AND THEN BECOMES ABSORBED BACK
INTO THE LONGWAVE TROUGH AND POSSIBLY GIVES US A CHANCE OF RAIN
NEXT TUESDAY THROUGH WEDNESDAY AS IT DOES.
(PREVIOUS DISCUSSION SUBMITTED AT 111 PM):
IT'S A LOVELY FALL DAY IN SOUTHERN CALIFORNIA - SUNNY SKIES WITH
NEAR NORMAL TEMPERATURES PREVAILING INTO THE WEEKEND. AN UPPER LEVEL
LOW WILL SETTLE JUST OFF THE COAST TODAY, PINCHING OFF FROM THE MAIN
TROUGH AS IT PASSES THROUGH THE FOUR CORNERS. WEAK OFFSHORE FLOW AND
INCREASING HEIGHTS TODAY HAS HELPED US WARM SIGNIFICANTLY FROM
THURSDAY, WITH HIGHS IN THE 70S AND 80S FOR MOST LOCATIONS. WINDS
SWITCH MORE ONSHORE FOR COASTAL AREAS SATURDAY AND SUNDAY, AND TEMPS
WILL CONTINUE TO WARM THROUGH THE WEEKEND, RETURNING TO NEAR NORMAL
FOR MID-OCTOBER. THE STATIONARY LOW WILL BEGIN TO SLIDE EASTWARD ON
MONDAY, ONLY COOLING TEMPERATURES A DEGREE OR TWO OVER SUNDAY'S
PEAK. AS THE LOW MOVES INTO CALIFORNIA TUESDAY AND INTO WEDNESDAY,
MEAGER MOISTURE ASSOCIATED WITH THE LOW MAY BE JUST ENOUGH FOR A FEW
RAIN SHOWERS IN THE HIGHER TERRAIN WHERE OROGRAPHIC LIFT MAY ASSIST,
BUT OTHERWISE, THIS SYSTEM LOOKS TO BE FAIRLY DRY. AS THE LOW MOVES
ACROSS, SUBSTANTIAL COOLING WILL BE OBSERVED, ESPECIALLY FOR
WEDNESDAY, WHEN HIGHS MAY ONLY REACH THE 60S FOR COASTAL AND
VALLEY AREAS. TIMING OF THE ARRIVAL OF THE LOW WILL INFLUENCE
TEMPERATURES DRASTICALLY FOR THE MIDDLE OF NEXT WEEK, ALONG WITH A
DEEPENING MARINE LAYER AND HOW FAR INLAND IT IS ABLE TO SPREAD.
EITHER WAY, HIGHS FOR MID-WEEK COULD BE ANYWHERE FROM 3-10 DEGREES
BELOW NORMAL.
AS THE SYSTEM MOVES UP AND OUT OF THE REGION THURSDAY, MORE ZONAL
FLOW SETTLES IN WITH VERY SLOW WARMING. A FEW MODELS INDICATE THAT
THERE MAY BE A SHORTWAVE TROUGH MOVE ACROSS LATE NEXT WEEK, BUT THE
REAL EYE-CATCHER IN THE LONG RANGE IS A MASSIVE LOW MOVING DOWN INTO
THE PACNW, HELPING USHER IN SUBSTANTIAL MOISTURE TO CALIFORNIA AS
EARLY AS NEXT WEEKEND. DON'T GET TOO EXCITED YET, AS CHANCES FOR
MEANINGFUL RAINFALL IN SOCAL REMAINS LOW THIS FAR OUT, BUT THIS WILL
BE SOMETHING TO KEEP A CLOSE EYE ON.
AVIATION
180300Z....CLEAR AND VFR CONDITIONS THROUGH LATE SATURDAY.
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.
UPDATE...STEWEY
PUBLIC...ZUBER
AVIATION/MARINE...WESTERINK
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