520
FXUS66 KSGX 130015
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
515 PM PDT MON OCT 12 2026
SYNOPSIS
A LOW PRESSURE SYSTEM MOVING THROUGH THE AREA AND INTO THE GREAT
BASIN WILL MAINTAIN COOL AND SHOWERY WEATHER TODAY, WITH SHOWERS
ENDING FROM THE NORTHWEST TONIGHT. IT WILL BE WARMER AND DRY FOR
WEDNESDAY THROUGH SATURDAY WITH DEVELOPING SANTA ANA WINDS
STRENGTHENING FOR FRIDAY INTO SATURDAY. MODERATE HEATRISK COULD
RETURN FOR THE COAST INTO THE WESTERN VALLEYS FOR FRIDAY THROUGH
SUNDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
..UPDATED AVIATION DISCUSSION
TONIGHT THROUGH WEDNESDAY...
THE AREA OF LOW PRESSURE IS CONTINUING TO SLIDE SLOWLY SOUTHWARD
JUST OFF THE COAST OF CENTRAL CALIFORNIA, AND WILL PROPAGATE MORE
EASTWARD BY LATER IN THE DAY, AND EVENTUALLY EXIT THE REGION. UNTIL
THEN, THERE WILL STILL BE A FEW LINGERING LIGHT TO MODERATE SHOWERS,
MAINLY WEST OF THE MOUNTAINS. A GENERAL CONSENSUS OF THE HIGH RES
MODELS SHOWS THE PRECIPITATION COMPLETELY COMING TO AN END BY EARLY
TOMORROW MORNING. ANY REMAINING SHOWERS SHOULD NOT AMOUNT TO ANYMORE
THAN AN ADDITIONAL TENTH OF AN INCH OR LESS FOR THE COASTAL AREAS
TO A QUARTER OF AN INCH FOR THE MOUNTAINS, WITH THE HIGHEST
AMOUNTS EXPECTED FOR THE WESTERN-FACING COASTAL SLOPES AND INLAND
FOOTHILLS. CLEARING TONIGHT WILL ALLOW FOR TEMPERATURES TO COOL
OFF EFFICIENTLY, AND LEAD TO OUR COLDEST NIGHT IN RECENT MONTHS,
WITH LOWS DIPPING DOWN INTO THE UPPER 40S TO LOWER 50S FOR SOME OF
THE HIGHER INLAND VALLEYS. WITH ANTECEDENT RAINFALL, THERE COULD
ALSO BE SOME AREAS OF PATCHY RADIATIONAL FOG ALSO DEVELOPING
WITHIN SOME OF THE HIGHER VALLEYS. HIGH PRESSURE WILL BUILD IN
OVER THE REGION THROUGH TOMORROW, WITH A GRADUAL WARMING, ALTHOUGH
HIGHS WILL STILL BE RUNNING AROUND 10 TO 15 DEGREES BELOW THE
SEASONAL AVERAGE FOR MOST LOCATIONS FOR THIS TIME OF YEAR FOR
TOMORROW DUE TO THE COLDER AIR ADVECTION BEHIND THE LOW. THE
MARINE LAYER FOR TONIGHT WILL FILL IN SLIGHTLY OVERNIGHT, BUT
REMAIN RATHER BROKEN AND DISPERSED, WITH A FEW ISOLATED SHOWERS
STILL BEING POSSIBLE THROUGH THE EARLY MORNING HOURS TOMORROW.
SKIES WILL FURTHER CLEAR BY TOMORROW AFTERNOON AS THE UPPER LEVEL
LOW PULLS AWAY FROM THE REGION, WITH DRYING CONDITIONS
ESTABLISHING THEMSELVES AS WE BEGIN TO TRANSITION INTO SANTA ANA
CONDITIONS.
THURSDAY THROUGH MONDAY...
HIGH PRESSURE IS GOING TO BEGIN TO BUILD IN OVER THE GREAT BASIN AS
THE UPPER LEVEL LOW BECOMES STALLED OUT OVER THE FOUR CORNERS
REGION. THIS WILL BEGIN TO ESTABLISH SANTA ANA CONDITIONS. BY
THURSDAY, HIGHS WILL STILL BE SLIGHTLY BELOW AVERAGE FOR THE
MOUNTAINS AND DESERTS, ALTHOUGH AROUND AVERAGE, AND EVEN SLIGHTLY
HIGHER FOR THE COASTAL LOCATIONS AS OFFSHORE WINDS SETTLE IN OVER
THE REGION. BY FRIDAY, A STRONG SUPERGRADIENT JET MAXIMA AT THE 300
MB LEVEL IS GOING TO MOVE IN FROM THE NORTH OVER CENTRAL CONUS, AND
FORCE THE U/L LOW TO CUT OFF AND RETROGRADE BACK TOWARDS THE
SOUTHWEST. THIS WILL HELP THE ENHANCE THE OFFSHORE WINDS ON FRIDAY
INTO EARLY SATURDAY, WITH SOME OF THE COASTAL AND INLAND BASINS
CLIMBING TO AFTERNOON TEMPERATURES BEING AS MUCH AS 15 DEGREES
ABOVE AVERAGE FOR FRIDAY AFTERNOON, AND POSSIBLE RETURN OF
MODERATE HEATRISK RETURNING TO PORTIONS OF THESE LOCATIONS. WINDS
WILL ALSO BE RATHER STRONG AND GUSTY FOR SOME OF THE HIGHER
TERRAIN AND WITHIN MOUNTAIN CANYONS AND PASSES, AND THERE MIGHT
EVEN NEED TO BE WIND ADVISORIES ISSUED FOR A FEW LOCATIONS, WHICH
WILL BE DECIDED IN THE NEXT DAY OR TWO ONCE THERE IS BETTER
AGREEMENT AND CONFIDENCE AS TO WHERE THESE WINDS WILL BE. RH
VALUES WILL DROP ON THURSDAY, BUT THEN SLIGHTLY INCREASE ON FRIDAY
AS THE RETROGRADED LOW TAPS INTO SOME SUBTROPICAL MOISTURE TO THE
SOUTH. HOWEVER, FIRE CONCERNS WITH THE STRONG AND GUSTY EASTERLY
WINDS WILL REMAIN ELEVATED FOR BOTH DAYS. THESE WINDS WILL BEGIN
TO SUBSIDE GOING INTO THE UPCOMING WEEKEND, AS MAX TEMPERATURES
BEGIN TO FLATLINE A BIT, WITH A GRADUAL COOLING OCCURRING EACH DAY
INTO EARLY NEXT WEEK. THERE WILL ALSO BE A VERY SLIGHT CHANCE OF
PRECIPITATION FOR THE MOUNTAINS AND DESERTS DURING THE AFTERNOON
HOURS ON FRIDAY AS A RESULT OF SOME MOISTURE BEING INTRODUCED,
ALONG WITH A SLIGHT INCREASE IN INSTABILITY, YET THIS WILL LIKELY
REMAIN EAST OF OUR CWA. THE RETURN OF ONSHORE FLOW GOING INTO LATE
SATURDAY/EARLY SUNDAY MAY RESULT IN THE ONSET OF SOME AREAS OF
DENSE FOG DURING THE EARLY MORNING HOURS. OTHERWISE, CONDITIONS
LOOK TO BE RATHER TRANQUIL IN COMPARISON AS WEAK RIDGING RETURNS
OVER THE REGION, WITH THE TRANSITION BACK INTO MORE ZONAL FLOW AND
TROUGHING UPSTREAM BECOMING THE PREDOMINANT FEATURES GOING INTO
THE EARLY PART OF NEXT WEEK.
AVIATION
130000Z...COASTAL/INLAND BASIN...SCT -SHRA TO CONTINUE THROUGH 07Z
FOR OC/IE, AND THROUGH 13Z THROUGH SAN DIEGO COUNTY. OTHERWISE, SCT-
BKN CLOUDS ~4-6 KFT MSL THROUGH EARLY TUESDAY, WITH TEMPORARILY MVFR
BASES/CIGS UNDER -SHRA. MOSTLY SKC AND VFR TUESDAY AFTERNOON.
MOUNTAINS...SCT -SHRA WILL CONTINUE THROUGH 06Z FOR NORTHERN AREAS
AND THROUGH 12Z IN SD COUNTY. BKN-OVC MVFR CIGS AND OBSCURED
TERRAIN WILL LINGER THROUGH 04-16Z TUE, CLEARING GRADUALLY FROM
NORTH TO SOUTH.
DESERTS...WEST WINDS UP TO 35 KTS (LOCALLY HIGHER THROUGH BANNING
PASS) TO CONTINUE ALONG THE DESERT SLOPES, WEAKENING 06-12Z TUE.
OTHERWISE, MOSTLY SKC AND VFR THROUGH THE TAF PERIOD.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH FRIDAY.
BEACHES
A COMBO SOUTHERLY AND WESTERLY SWELL WILL CONTINUE THROUGH TUESDAY,
GENERATING SURF 3-5 FEET WITH LOCAL SETS TO 7 FEET, ALONG WITH
STRONG RIP CURRENTS. LATE MORNING HIGH TIDES NEAR 7 FEET WILL
CONTINUE, PRODUCING MINOR COASTAL FLOODING. CHECK THE COASTAL FLOOD
ADVISORY FOR DETAILS.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY UNTIL 2 PM PDT TUESDAY FOR ORANGE COUNTY
COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
PZ...NONE.
PUBLIC...STEWEY
AVIATION/MARINE/BEACHES...WESTERINK
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