970
FXUS66 KSGX 190453
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
853 PM PST WED DEC 18 2024
SYNOPSIS
SANTA ANA WINDS WILL CONTINUE TO DECREASE INTO THURSDAY MORNING.
LOCALLY BREEZY EAST TO NORTHEASTERLY WINDS AND LOW RELATIVE
HUMIDITY WILL LINGER INTO THURSDAY, CREATING ELEVATED FIRE WEATHER
CONDITIONS. CONDITIONS WILL GRADUALLY COOL THURSDAY THROUGH THE
WEEKEND. MARINE LAYER LOW CLOUDS AND FOG MAY RETURN ALONG THE
COAST TONIGHT, INCREASING IN COVERAGE OVER THE WEEKEND. GUSTY
WESTERLY WINDS OVER THE MOUNTAINS INTO THE DESERTS AND A CHANCE
OF SHOWERS ENTERS THE FORECAST ON TUESDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE
DENSE FOG CONTINUES TO CREEP NORTHWARD ALONG THE SAN DIEGO COUNTY
COAST. A WEAK COASTAL EDDY IS TRYING TO HELP LIFT SOME OF THIS
FOG BUT IS DOING A POOR JOB THUS FAR. THE FOG WILL STICK TO
COASTAL AREAS THROUGH THIS EVENING, REACHING INTO ORANGE COUNTY
OVERNIGHT, WITH SOME POTENTIAL IMPROVEMENTS BY MORNING. IT WAS A
VERY WARM DAY FOR SOME OF OUR INLAND VALLEYS TODAY AS OFFSHORE
FLOW WEAKENED OVER THE AREA. HIGHS MADE IT WELL INTO THE 80S FOR
SOME LOCATIONS WITH 7 RECORDS SET OVER THE AREA, INCLUDING PALM
SPRINGS, ESCONDIDO, AND RAMONA. ONSHORE FLOW WILL INCREASE BY
THURSDAY, LEADING TO SOME SUBTLE COOLING FOR LOWER ELEVATIONS,
THOUGH STILL WARM. RAMONA'S RECORD HIGH FOR THURSDAY IS 82 SET IN
2005, WHICH HAS ABOUT A 60% CHANCE OF BEING BROKEN.
WE LOOK TOWARD THE CHRISTMAS HOLIDAY FOR OUR NEXT CHANCE FOR
PRECIPITATION. ENSEMBLE MODEL GUIDANCE HAS BEEN QUITE CONSISTENT
AND EVEN INCREASED CHANCES FOR PRECIPITATION FOR SOME SPOTS BY
LATER ON CHRISTMAS EVE INTO EARLY CHRISTMAS MORNING. WHILE NO
SIGNIFICANT PRECIPITATION IS EXPECTED, SANTA MAY GET A LITTLE WET
WHILE DELIVERING PRESENTS TO ALL THOSE SNUG IN THEIR BEDS.
PREVIOUS DISCUSSION (139 PM THURSDAY)
FRIDAY THROUGH THE WEEKEND, THE MARINE LAYER IS EXPECTED TO SLOWLY
REBUILD AND SPREAD LOW CLOUDS AND FOG INTO THE WESTERN VALLEYS BY
SUNDAY MORNING.
WINDS THIS AFTERNOON HAVE WEAKENED AND BECOME MUCH MORE LOCALIZED.
LOCALLY BREEZY EAST TO NORTHEAST WINDS ON THE MOUNTAIN FOOTHILLS AND
BELOW PASSES WILL CONTINUE INTO EARLY THURSDAY. HIGHS TODAY ARE
EXPECTED TO WARM A FEW TO AROUND 5 DEGREES FOR THE INLAND AREAS WITH
THE COAST AND WESTERN VALLEYS ANOTHER 5 TO 10 DEGREES WARMER THAN
TUESDAY, REACHING THE LOWER TO MID 80S FOR PORTIONS OF THE VALLEYS
AND INLAND COASTAL AREAS, AS MUCH AS 12 TO 18 DEGREES ABOVE AVERAGE.
FOR THE WEEKEND, RIDGING ALOFT IS EXPECTED OVER THE DESERT SOUTHWEST
WITH AN UPPER LEVEL TROUGH OFF THE COAST OF THE PACIFIC NORTHWEST.
THE MAIN IMPACTS FOR SOUTHERN CALIFORNIA FROM THAT TROUGH WILL BE AN
INCREASE IN HIGH CLOUD COVERAGE AND A FEW DEGREES OF COOLING (MOST
NOTICEABLE FOR PLACES WEST OF THE MOUNTAINS). WEAK RIDGING ALOFT
WILL MOVE OVER SOUTHERN CALIFORNIA FOR MONDAY, BRINGING A FEW
DEGREES OF WARMING. FOR TUESDAY A QUICK MOVING TROUGH OF LOW
PRESSURE WILL MOVE ACROSS THE WEST COAST. THERE IS SOME UNCERTAINTY
IN HOW FAR SOUTH THE LOW WILL DIG, WHICH INTRODUCES UNCERTAINTY
SURROUNDING OUR CHANCES OF PRECIPITATION(CURRENTLY AT 25 TO 35
PERCENT IN AND WEST OF THE MOUNTAINS) BUT AN UPTICK IN WINDS FOR THE
MOUNTAINS AND DESERTS IS LOOKING LIKELY. OVERALL, THERE IS FAIRLY
HIGH CONFIDENCE IN TIMING OF WIND AND ANY POTENTIAL PRECIPITATION
OCCURRING TUESDAY AND TUESDAY NIGHT, WITH LOW CONFIDENCE IN WIND
SPEEDS AND PRECIPITATION AMOUNTS.
AVIATION
190500Z....COASTS/VALLEYS...A SURGE OF FOG AND LOW CLOUDS HAS MOVED
NORTH ALONG THE COAST AND HAS STARTED TO MOVE INLAND AS A WEAK
CATALINA EDDY HAS SET UP. THIS FOG IS EXPECTED TO REMAIN OVER THE
WATER AND COASTAL REGIONS TONIGHT THROUGH THE MORNING HOURS. CLEARING
ALONG THE COASTS SHOULD OCCUR BY 15-17Z, WITH VFR AND FEW250
PREVAILING BEYOND THAT.
MOUNTAINS/DESERTS
MOSTLY CLEAR SKIES THROUGH THURSDAY MORNING.
AREAS OF NORTHEAST WINDS ABOVE 25 MPH WILL CONTINUE THIS EVENING,
BUT WILL CONTINUE TO DECREASE THROUGH THE NIGHT. HIGH CLOUDS RETURN
THURSDAY AFTERNOON WITH BASES GENERALLY AT OR ABOVE 20,000FT MSL.
MARINE
DENSE FOG POSSIBLE TONIGHT AND THURSDAY NIGHT WITH VISIBILITY
DOWN TO 1 NM. OTHERWISE, NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH
SATURDAY. LONG PERIOD WEST SWELL LATE SATURDAY WILL GENERATE SEAS OF
8-11 FEET ON SUNDAY AND MONDAY, PRIMARILY FOR THE OUTER COASTAL
WATERS AND NEAR SAN CLEMENTE ISLAND. SEAS BEGIN TO LESSEN MONDAY
NIGHT INTO TUESDAY.
FIRE WEATHER
ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE INTO THURSDAY WITH
LOCAL WIND GUSTS UP TO 35 MPH BELOW PASSES AND ON MOUNTAIN FOOTHILLS
COMBINED WITH MINIMUM DAYTIME RELATIVE HUMIDITY 10 TO 15 PERCENT FOR
THE INLAND VALLEYS AND PENINSULAR MOUNTAIN RANGES. FOR FRIDAY
THROUGH EARLY NEXT WEEK, ONSHORE FLOW WILL RETURN SPREADING GRADUAL
COOLING AND HIGHER COASTAL HUMIDITY INLAND. WESTERLY WINDS ARE
EXPECTED TO INCREASE OVER THE MOUNTAINS AND LOCALLY INTO THE DESERTS
TUESDAY, ALONG WITH A 20 TO 35 PERCENT CHANCE OF RAIN SHOWERS
(HIGHEST CHANCES IN THE MOUNTAINS).
BEACHES
16-17 SECOND PERIOD WEST SWELL (270-280 DEGREES) VERY EARLY SUNDAY
WILL BRING HIGH SURF OF 8 TO 10 FEET WITH LOCALLY HIGHER SETS TO
BOTH SAN DIEGO COUNTY AND ORANGE COUNTY BEACHES FOR SEVERAL DAYS.
SURF WILL SUBSIDE A BIT BY WEDNESDAY, BUT REINFORCING LONG PERIOD
SWELLS MAY MAINTAIN ELEVATED/HIGH SURF FOR MUCH OF NEXT WEEK. HIGH
RISK OF STRONG RIP CURRENTS AND DANGEROUS SWIMMING CONDITIONS, WITH
ADDITIONAL COASTAL IMPACTS POSSIBLE.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
PUBLIC...APR/CO
AVIATION/MARINE...SUK
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