102
FXUS66 KSGX 202145
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
145 PM PST FRI DEC 20 2024
SYNOPSIS
AREAS OF LOW CLOUDS AND DENSE FOG ARE EXPECTED WITHIN A FEW MILES OF
THE COAST TONIGHT INTO SATURDAY MORNING. NIGHT AND MORNING LOW
CLOUDS AND FOG ARE EXPECTED EACH DAY INTO EARLY NEXT WEEK, GRADUALLY
SPREADING FURTHER INLAND EACH DAY THROUGH SUNDAY. HIGH TEMPERATURES
WILL DECREASE A FEW DEGREES EACH DAY THROUGH SUNDAY. GUSTY WESTERLY
WINDS OVER THE MOUNTAINS AND LOCALLY INTO THE DESERTS AND A CHANCE
OF SHOWERS ARE EXPECTED TUESDAY. DRY CONDITIONS SHOULD RETURN BY
WEDNESDAY, BUT THERE IS A MINOR CHANCE OF SHOWERS IN THE FORECAST
FOR THE END OF NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
A TROUGH OF LOW PRESSURE APPROACHING THE COAST OF THE PACIFIC
NORTHWEST WILL HELP INCREASE ONSHORE FLOW AND BREAK DOWN THE WEAK
RIDGING OVER SOCAL BY SATURDAY. THAT WILL HELP SPREAD LOW CLOUDS
AND FOG FURTHER INLAND, REACHING INTO PORTIONS OF THE VALLEYS BY
SUNDAY. FOR TONIGHT INTO SATURDAY MORNING, THE MARINE LAYER IS
EXPECTED TO DEEPEN A LITTLE. THIS SHOULD SPREAD LOW CLOUDS AND FOG
CLOSER TO THE I-15 CORRIDOR IN SAN DIEGO COUNTY AND EAST OF THE
405 IN ORANGE COUNTY. THE HREF IS SHOWING A 40 TO 50 PERCENT
CHANCE OF DENSE FOG FORMING TONIGHT INTO SATURDAY MORNING IN THE
AFOREMENTIONED AREAS.
A GRADUAL COOLING TREND IS EXPECTED THROUGH THE WEEKEND AS THE UPPER
LEVEL TROUGH MOVES ACROSS THE PACIFIC NORTHWEST. HIGHS IN THE
WESTERN VALLEYS WILL BE IN THE LOWER 70S BY SUNDAY. OTHER
COMMUNITIES ACROSS THE COAST, MOUNTAINS AND DESERTS WILL SEE SIMILAR
TEMPERATURE READINGS INTO THE WEEKEND: HIGHS NEAR 80 IN THE LOWER
DESERTS, NEAR 70 IN THE HIGH DESERT, AND MID 60S ALONG THE BEACHES.
PERIODS OF HIGH CLOUDS CAN BE EXPECTED IN ADDITION TO THE GRADUAL
COOLING. 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. LATEST GUIDANCE IS INDICATING LIGHT RAIN IS POSSIBLE
FROM THE COAST TO THE MOUNTAINS. ONSHORE WESTERLY WINDS WILL
INCREASE TUESDAY AND PEAK TUESDAY NIGHT, STRONGEST IN THE MOUNTAINS,
THROUGH PASSES, AND LOCALLY INTO THE DESERTS. GUIDANCE IS FAIRLY
CONSISTENT ON THE TIMING BEING TUESDAY AFTERNOON AND EVENING FOR
BOTH THE UPTICK IN WIND AND PRECIPITATION. SNOW LEVELS ARE EXPECTED
TO STAY ABOVE 7000 FT. GUIDANCE FROM THE NBM HAS TRENDED DRIER SINCE
YESTERDAY, WITH A 25 PERCENT CHANCE (DOWN FROM AROUND 40 PERCENT
YESTERDAY) OF AT LEAST 0.25" OF RAIN IN THE MOUNTAINS OVER A 24 HOUR
PERIOD ENDING WEDNESDAY MORNING. CHANCES OF AT LEAST 0.10" OF RAIN
ACCUMULATING OVER A 24 HOUR PERIOD ENDING WEDNESDAY MORNING FOR THE
COAST AND VALLEYS IS STILL AROUND 20 TO 25 PERCENT. 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 NORMAL FOR THIS
TIME OF YEAR WEST OF THE MOUNTAINS AND 3 TO 5 DEGREE WARMER THAN
NORMAL IN THE DESERTS. LOWER DESERT LOCATIONS WILL HIGHS IN THE 70S
WITH WIDESPREAD 60S WEST OF THE MOUNTAINS. SIMILAR TEMPERATURES CAN
BE EXPECTED THROUGH THE END OF THE WEEK AS THE TROUGHING PATTERN
REMAINS. ANOTHER WAVE MAY DIG DEEP ENOUGH THROUGH THE REGION BY
THURSDAY AFTERNOON OR EVENING TO BRING ANOTHER MINOR CHANCE (AROUND
15 PERCENT) FOR PRECIPITATION IN AND WEST OF THE MOUNTAINS.
AVIATION
202130Z....COAST...VERY LOW CLOUDS BASED AT 200-300 FEET MSL WITH
TOPS TO 600 FEET, AND AREAS OF DENSE FOG WITH VIS 0-3SM WILL DEVELOP
AFTER 01Z AND SPREAD LOCALLY INLAND OVERNIGHT. CONFIDENCE IS HIGH
THAT LIFR CONDITIONS WILL OCCUR AT SNA AND CRQ, AND MODERATE AT SAN.
SCATTER OUT SATURDAY 17-19Z.
OTHERWISE...VFR CONDITIONS WILL PREVAIL THROUGH SATURDAY, BUT WITH
AN INCREASE IN HIGH CLOUDS ABOVE 20000 FEET MSL.
MARINE
PATCHY DENSE FOG WITH VISIBILITY BELOW 1 NM AT TIMES WILL CONTINUE
THROUGH SATURDAY MORNING. LONG PERIOD WEST SWELLS OF 8-11 FEET ARE
EXPECTED SUNDAY THROUGH TUESDAY NIGHT, HIGHEST IN THE OUTER COASTAL
WATERS.
BEACHES
LARGE SURF OF 6-12 FEET WITH LOCALLY HIGHER SETS WILL ARRIVE SUNDAY
AND CONTINUE INTO WEDNESDAY. THIS WILL MAKE SWIMMING HAZARDOUS AND
POSE A COASTAL FLOODING THREAT. CHECK THE HIGH SURF ADVISORY FOR
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 SATURDAY TO 4 AM PST WEDNESDAY FOR
ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
PZ...NONE.
PUBLIC...CO
AVIATION/MARINE/BEACHES...MM
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