167
FXUS66 KSGX 212132
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
132 PM PST SAT DEC 21 2024
SYNOPSIS
PATCHY DENSE FOG IS POSSIBLE ALONG THE IMMEDIATE COAST THIS
AFTERNOON, WITH HIGH CLOUDS ELSEWHERE. NEAR AVERAGE TEMPERATURES
EXPECTED NEAR THE COAST THROUGH EARLY NEXT WEEK WITH ABOVE AVERAGE
TEMPERATURES AWAY FROM THE COAST. BREEZIER, COOLER, AND WETTER
WEATHER IS EXPECTED FOR TUESDAY. DRY WEATHER IS EXPECTED FOR THE
MIDDLE TO END OF NEXT WEEK, WITH A WARMING TREND INTO NEXT WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
ONSHORE FLOW WILL INCREASE INTO SUNDAY AS A WEAK TROUGH PASSES TO
OUR NORTH. THAT WILL HELP SPREAD LOW CLOUDS AND FOG FURTHER INLAND
TONIGHT INTO SUNDAY MORNING REACHING INTO PORTIONS OF THE WESTERN
VALLEYS. DENSE FOG IS EXPECTED TO BECOME LESS LIKELY FOR THE
IMMEDIATE COAST, ALTHOUGH PATCHY FOG THAT LIMITS VISIBILITY COULD
STILL OCCUR. FOR SAN DIEGO COUNTY AREAS OF DENSE FOG COULD REACH AS
FAR INLAND AS THE INTERSTATE 15 CORRIDOR AND FOR ORANGE COUNTY
BETWEEN INTERSTATE 405 AND INTERSTATE 5.
PERIODS OF HIGH CLOUDS CAN BE EXPECTED THROUGH SUNDAY. A FEW DEGREES
OF COOLING OR MINIMAL CHANGE IN TEMPERATURES IS EXPECTED FOR SUNDAY.
WEAK RIDGING ALOFT WILL MOVE OVER SOUTHERN CALIFORNIA FOR MONDAY,
BRINGING A FEW DEGREES OF WARMING.
ON TUESDAY A QUICK MOVING TROUGH OF LOW PRESSURE WILL MOVE ACROSS
THE WEST COAST BRINGING BREEZY, WET, AND COOL CONDITIONS TO THE
AREA. ONSHORE WESTERLY WINDS WILL INCREASE TUESDAY AND PEAK TUESDAY
NIGHT, STRONGEST IN THE MOUNTAINS, THROUGH PASSES, AND LOCALLY INTO
THE DESERTS. PRELIMINARY GUIDANCE SHOWS PEAK WIND GUSTS OF 35-45
MPH, LOCALLY UP TO 55 MPH IN WIND PRONE LOCATIONS. GUIDANCE IS
FAIRLY CONSISTENT ON THE TIMING BEING TUESDAY AFTERNOON AND EVENING
FOR BOTH THE UPTICK IN WIND AND PRECIPITATION. DETERMINISTIC
INTEGRATED WATER VAPOR TRANSPORT GUIDANCE FOR BOTH THE GFS AND ECMWF
IS SHOWING A WEAK MOISTURE SURGE REACHING THE SOUTHERN CALIFORNIA
COAST TUESDAY EVENING. ALMOST ALL INDIVIDUAL ENSEMBLE MEMBERS FOR
THE ECMWF AND GEFS ARE SHOWING MEASURABLE PRECIPITATION FOR PLACES
WEST OF THE MOUNTAINS FOR TUESDAY AFTERNOON/NIGHT. THERE DOES STILL
REMAIN SOME UNCERTAINTY IN RAINFALL AMOUNTS, ALTHOUGH MOST GUIDANCE
IS INDICATING RAINFALL WILL BE LIGHT. FORECAST RAINFALL TOTALS HAVE
INCREASED SLIGHTLY SINCE THIS MORNING. FOR THE COAST AND VALLEYS
TOTALS ARE EXPECTED TO BE 0.05-0.12", WITH TOTALS 0.20-0.30" ON THE
COASTAL SLOPES OF THE MOUNTAINS. A DUSTING OF SNOW IS EXPECTED ABOVE
7000 FT. THE TROUGH IS EXPECTED TO QUICKLY EXIT TO THE EAST, LEAVING
DRY CONDITIONS IN IT'S WAKE FOR MUCH OF WEDNESDAY.
TEMPERATURES ON WEDNESDAY ARE EXPECTED TO BE NEAR TO SLIGHTLY BELOW
NORMAL FOR THIS TIME OF YEAR WEST OF THE MOUNTAINS AND 3 TO 7 DEGREE
WARMER THAN NORMAL IN THE DESERTS. LOWER DESERT LOCATIONS WILL HAVE
HIGHS IN THE 70S WITH WIDESPREAD 60S WEST OF THE MOUNTAINS. A
GRADUAL WARMING TREND IS EXPECTED THURSDAY THROUGH SATURDAY AS
RIDGING BUILDS OVER CALIFORNIA.
AVIATION
212130Z....COASTS/VALLEYS...LOW CLOUDS HAVE ERODED FOR THE LARGE
PART THIS AFTERNOON, THOUGH HAZY CONDITIONS LINGER ALONG COASTAL
AREAS. LOW CLOUDS AND FOG REDEVELOP THIS EVENING, POSSIBLY AS EARLY
AS 00-01Z, WITH MUCH HIGHER CONFIDENCE IN CIGS AFTER 03-04Z SUN.
CLOUDS WILL REACH FURTHER INLAND OVERNIGHT, UP TO ABOUT 10 MILES
FROM THE COAST. BASES AND VIS EXPECTED TO BE SLIGHTLY HIGHER
OVERNIGHT COMPARED TO THIS MORNING, BUT BASES WILL STILL BE LOW AT
300-600 FT MSL WITH WIDESPREAD VIS RESTRICTIONS 2-5 SM LIKELY. DENSE
FOG WITH VIS UNDER 1 SM LOOKS LESS LIKELY THAN THIS MORNING FOR THE
IMMEDIATE COAST, BUT IS STILL POSSIBLE 11-15Z SUN. CLOUDS CLEARING
AGAIN FROM INLAND AREAS 17-19Z SUN, BUT HAZY/MISTY CONDITIONS WITH
VIS RESTRICTIONS 4-6 SM COULD LINGER AT COASTAL SITES, AND PATCHY
LOW CLOUDS AND FOG WILL REMAIN ALONG SOME BEACHES INTO THE
AFTERNOON.
MOUNTAINS/DESERTS
VFR CONDITIONS WILL PREVAIL TODAY INTO
SUNDAY, WITH HIGH CLOUDS ABOVE 20000 FEET MSL.
MARINE
ROUNDS OF PATCHY OVERNIGHT/MORNING FOG REMAINS POSSIBLE THROUGH AT
LEAST TUESDAY. VISIBILITY IN FOG TONIGHT INTO EARLY SUNDAY MORNING
EXPECTED TO REMAIN AT OR ABOVE 1 SM.
LONG PERIOD WEST SWELLS OF 8-11 FEET WILL BUILD IN LATE TONIGHT,
LINGERING SUNDAY THROUGH TUESDAY NIGHT, WITH THE HIGHEST SWELLS IN
THE OUTER COASTAL WATERS WHERE A SMALL CRAFT ADVISORY IS IN PLACE. 8-
9 FEET WAVES POSSIBLE WITHIN 10-30 NM OF THE COAST BUT SHOULD STILL
BE FAR ENOUGH OFFSHORE TO LIMIT ANY NEARSHORE IMPACTS. WIND GUSTS OF
20-25 KTS ARE EXPECTED TUESDAY NIGHT IN THE OUTER COASTAL WATERS.
BEACHES
LONG PERIOD (16-19 SECOND) WEST TO NORTHWEST SWELLS (280-290
DEGREES) ARRIVE EARLY SUNDAY AND LINGERS INTO NEXT WEEK, RESULTING
IN HIGH SURF OF 6-12 FEET WITH LOCALLY HIGHER SETS CONTINUING
THROUGH WEDNESDAY. THIS WILL MAKE SWIMMING HAZARDOUS AND POSE A
COASTAL FLOODING THREAT. SEE THE HIGH SURF ADVISORY FOR MORE DETAILS.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 4 AM PST WEDNESDAY
FOR ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL
AREAS.
PZ...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 AM PST
WEDNESDAY FOR WATERS FROM SAN MATEO POINT TO THE MEXICAN
BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE
ISLAND.
PUBLIC...CO
AVIATION/MARINE/BEACHES...CSP
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