791
FXUS66 KLOX 131204
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
504 AM PDT MON OCT 13 2025
SYNOPSIS
13/330 AM.
AN EARLY SEASON STORM SYSTEM IN THE PACIFIC NORTHWEST WILL DIG
SOUTH INTO THE REGION THROUGH TUESDAY. PERIODS OF RAIN AND HIGH
ELEVATION SNOW, HEAVY AT TIMES, WILL DEVELOP FROM NORTH TO SOUTH
FROM THIS AFTERNOON THROUGH TUESDAY. GUSTY SOUTHERLY WINDS ARE
LIKELY TO DEVELOP THIS EVENING THROUGH TUESDAY AHEAD OF AND ALONG
THE SYSTEM'S COLD FRONT. COOLER TEMPERATURES WITH DRIER
CONDITIONS WILL LINGER INTO THURSDAY, THEN A WARMING TREND WILL
DEVELOP FOR THE END OF THE WEEK.
SHORT TERM (TDY-WED)
13/329 AM.
THE LATEST SATELLITE IMAGERY SHOWS AN UPPER-LEVEL TROUGH DIGGING
SOUTH OFF THE OREGON COAST EARLY THIS MORNING. A COLD FRONTAL
BOUNDARY CAN BE SEEN STRETCHING FROM NEAR PORTLAND, OREGON OUT TO
THE SOUTHWEST AND WEST. THIS FRONTAL BOUNDARY AND THE ASSOCIATED
UPPER-LEVEL TROUGH WILL DIG SOUTH THROUGH TUESDAY, BOTTOMING OUT
OVER CENTRAL CALIFORNIA TUESDAY AFTERNOON. LIGHT TO MODERATE PRE-
FRONTAL RAIN COULD START OVER THE SOUTHLAND AS EARLY AS THIS
EVENING, BUT THE HEAVIEST RAINFALL IS EXPECTED ALONG THE COLD
FRONT, WHICH WILL ARRIVE ALONG THE CENTRAL COAST LATE THIS
AFTERNOON AND EARLY THIS EVENING. WITH HIGH-RESOLUTION MULTI-MODEL
ENSEMBLE MEMBERS ALL INDICATING RAIN SPREADING OVER THE REGION
SPREADING NORTH TO SOUTH FROM THIS AFTERNOON THROUGH TUESDAY
AFTERNOON, POPS HAVE BEEN NUDGED HIGHER TO BETWEEN 90 AND 100
PERCENT ALONG THE FRONTAL BOUNDARY. VIRTUALLY EVERY LOCATION IN
THE FOUR COUNTY AREA WILL RECEIVE MEASURABLE RAINFALL THROUGH
TUESDAY MORNING.
STORM TOTAL RAINFALL AMOUNTS ARE EXPECTED TO RANGE FROM 0.75 INCH
TO 1.50 INCHES FOR THE COASTAL AND VALLEYS WITH UP 1.50 TO 3.00
INCHES IN THE MOUNTAINS. LOCAL AMOUNTS TO 4.00 INCHES ARE POSSIBLE
ALONG SOUTH-FACING SLOPES ACROSS THE SOUTHLAND AND INTO SANTA
YNEZ RANGE IN SANTA BARBARA COUNTY. THERE IS LESS CERTAINTY WITH
CONVECTIVE ELEMENTS OF THE BAND, BUT THERE IS MODERATE TO HIGH
CONFIDENCE THAT A BURST OF HEAVY RAINFALL WITH A QUASI-LINEAR
CONVECTIVE SYSTEM (QLCS) WILL DEVELOP OVERNIGHT TONIGHT INTO
TUESDAY. RAINFALL TOTALS COULD GO HIGHER THAN THE RANGE STATED IF
THE FRONT SLOWS DOWN OVER THE REGION AND COULD BE LESS THAN THE
RANGE STATED IF THE FRONT ACCELERATES THROUGH THE REGION. A
DIFLUENT FLOW PATTERN ALOFT WILL AID LIFT AS THE FRONT APPROACHES
THE REGION AND POSSIBLY ALLOW FOR ISOLATED THUNDERSTORMS TO
DEVELOP. RAINFALL RATES WILL GENERALLY RANGE BETWEEN 0.25-0.50
INCH PER HOUR, BUT SOME OF THE HIGHER RESOLUTION MODELS CONTINUE
TO INDICATE POTENTIALLY HIGHER RATES OF 0.50-1.00 INCH PER HOUR OR
GREATER. SUB-HOURLY RATES COULD BE QUITE INTENSE WITH THE
POSSIBILITY THAT SOME LOCATIONS COULD RECEIVE A THIRD TO TWO-
THIRDS OF AN INCH OF RAINFALL IN A VERY SHORT TIME. A FLOOD WATCH
REMAINS IN EFFECT FOR THE RECENT BURN AREAS FROM 8 PM TONIGHT
THROUGH 3 PM TUESDAY AS RAINFALL RATES COULD REACH OR EXCEED USGS
THRESHOLDS FOR AREA BURN SCARS. SIGNIFICANT MUD AND DEBRIS FLOWS
FROM RECENT BURN SCARS, INCLUDING THE GIFFORD, MADRE, LAKE,
PALISADES, FRANKLIN, EATON, AND BRIDGE BURN SCARS COULD DEVELOP.
WITH THE DIFLUENT FLOW PATTERN ALOFT AND THE THUNDERSTORM
POTENTIAL IN PLACE, PERIODS OF HEAVY RAINFALL, DANGEROUS
LIGHTNING, AND GUSTY WINDS WILL BE IN PLAY WITH THIS STORM.
MARGINAL WIND SHEAR PARAMETERS ARE PRESENT FOR THE POTENTIAL FOR
WEAK TORNADOES OR WATERSPOUTS TO DEVELOP TONIGHT ALONG THE CENTRAL
COAST AND LATE TONIGHT AND EARLY TUESDAY MORNING ALONG THE SOUTH
COAST OF CALIFORNIA. SLIGHTLY MORE FAVORABLE DIRECTIONAL AND SPEED
SHEAR DEVELOPS ACROSS THE SOUTHLAND AFTER MIDNIGHT TONIGHT
THROUGH MID- MORNING ON TUESDAY. THE TOPOGRAPHIC FEATURES OF THE
LOS ANGELES BASIN AND THE GREATER SOUTH COAST BASIN CAN ENHANCE
WIND SHEAR PARAMETERS AND AID TORNADIC DEVELOPMENT IN STORMS. AS
COLDER AIR MASS ALOFT MOVES INTO THE REGION ON TUESDAY AFTERNOON
AND EVENING, THE POTENTIAL FOR BRIEF HEAVY DOWNPOURS WITH SMALL
HAIL COULD ENTER THE PICTURE, WHILE GUSTY AND ERRATIC WINDS AND
DANGEROUS LIGHTNING WILL CONTINUE TO BE HAZARDS.
SOUTHERLY WINDS WILL INCREASE THROUGH TODAY AND TONIGHT AHEAD OF
THE FRONT. THERE IS THE POSSIBILITY OF HIGH WIND WARNING LEVEL
WINDS ACROSS THE MOUNTAINS TONIGHT AND INTO TUESDAY MORNING,
ESPECIALLY GIVEN THE POSSIBILITY OF THE QLCS MOVING OVER THE
REGION TONIGHT. DOWNBURST WINDS WITH THE CONVECTIVE SYSTEM, SHOULD
IT DEVELOP, COULD DOWN TREES, TREE LIMBS, AND POWER LINES. FOR
NOW, A WIND ADVISORY WAS ADDED FOR THE ANTELOPE VALLEY AND
ADJACENT FOOTHILLS FROM NOON TODAY THROUGH 10 PM TONIGHT FOR PRE-
FRONTAL WINDS. THE GREATEST AREA OF CONCERN WOULD BE THE
POTENTIAL FOR MOUNTAIN WAVE ACTIVITY ALONG THE INTERIOR SLOPES OF
THE SAN GABRIEL MOUNTAINS THIS AFTERNOON AND EVENING. FOOTHILL
COMMUNITIES SUCH AS VALYERMO, PEARBLOSSOM, CRYSTALAIRE, AND LAKE
PALMDALE MAY BE PARTICULARLY VULNERABLE GIVEN THE WIND DIRECTION.
WITH COLDER AIR ALOFT MOVING IN ALONG THE FRONT, LIGHT TO MODERATE
SNOWFALL ACCUMULATIONS ARE POSSIBLE ABOVE THE 6000 FOOT ELEVATION
LEVEL AND WHEN COMBINED WITH THE WINDS ALONG THE FRONT, TRAVEL
COULD END UP BEING TREACHEROUS AT TIMES ON HIGH MOUNTAIN
ROADWAYS, SUCH AS THE ANGELES CREST HIGHWAY AND LOCKWOOD VALLEY
ROAD. A WINTER WEATHER ADVISORY WAS CONSIDERED FOR THE HIGHER
ELEVATIONS OF THE SAN GABRIEL MOUNTAINS AND THE VENTURA COUNTY
MOUNTAINS, BUT GIVEN THE MARGINAL CONDITIONS, THE DECISION WAS
TABLED FOR NOW TO ALLOW FOR MORE DATA TO ARRIVE. SNOWFALL AMOUNTS
COULD RANGE BETWEEN 1 AND 4 INCHES WITH THIS STORM WITH ISOLATED
AMOUNTS UP TO 6 INCHES.
THERE IS AN OUTSIDE CHANCE THAT THE SHOWER THREAT COULD LINGER
ACROSS THE LOS ANGELES BASIN INTO WEDNESDAY AS THE TRAILING VORT
MAX MOVES OVER THE REGION. DRIER CONDITIONS SHOULD DEVELOP
THROUGH THE DAY WITH COOLER TEMPERATURES LINGERING ACROSS THE
REGION FOR WEDNESDAY.
LONG TERM (THU-SUN)
13/331 AM.
WEAK TO LOCALLY MODERATE OFFSHORE FLOW SHOULD SET UP BETWEEN
WEDNESDAY NIGHT AND INTO THURSDAY MORNING. CURRENTLY, WINDS LOOK
TO BE SUB-ADVISORY FOR THURSDAY MORNING AND NO ADVISORIES LOOKS TO
ISSUED. THE FIRST FROST OF THE SEASON COULD OCCUR FOR SOME
INTERIOR VALLEY AND WIND SHELTERED AREAS ON THURSDAY MORNING AS
CLEAR SKIES WILL MAKE RADIATIVE COOLING PROCESSES MUCH MORE
EFFICIENT. PATCHY FROST WAS ADDED TO A FEW SPOTS IN THE ANTELOPE
VALLEY AND THE SAN LUIS OBISPO COUNTY INTERIOR VALLEYS, BUT THIS
WILL NEED TO LOOKED AT CLOSER AS WE MOVE FORWARD INTO THE WEEK.
OTHERWISE, HIGH PRESSURE ALOFT BUILDING INTO THE REGION WILL BRING
A WARMING TREND FOR LATE WEEK. TEMPERATURES COULD WARM TO NEAR
NORMAL ON FRIDAY OR SATURDAY.
AVIATION
13/1204Z.
AT 0403Z AT KLAX, THE MARINE LAYER WAS 1500 FT DEEP. THE TOP OF
THE INVERSION WAS NEAR 2000 FT WITH A TEMPERATURE OF 19 C.
LOW CONFIDENCE IN THE 12Z TAFS FOR THE COASTAL AND VALLEYS SITES
AND MODERATE CONFIDENCE IN THE DESERT SITES.
EXPECTING SHRA/RA AFTER 00Z TUE ALONG CENTRAL COAST WITH MVFR
CONDITIONS AND PERIODS OF IFR POSSIBLE AT TIMES. AROUND A 30%
CHANCE OF TSRA DURING THIS TIMEFRAME FOR KPRB, KSBP, KSMX, & KSBA.
EXPECT VISIBILITY REDUCTIONS UNDER HEAVY RAINFALL. BRIEF LIFR
CONDITIONS CANNOT BE RULED OUT.
LLWS AND TURBULENCE IS POSSIBLE AS FRONT APPROACHES AND NEAR ANY
THUNDERSTORMS THAT DEVELOPS.
LOW TO MODERATE CONFIDENCE IN WIND FORECASTS. WIND GUSTS MAY BE
OFF 5 TO 10 KNOTS AND/OR DIRECTION BY 30 DEGREES, ESPECIALLY FOR
COAST AND VALLEY SITES AFTER 00Z TUESDAY - AS FRONT APPROACHES.
KLAX...LOW TO MODERATE CONFIDENCE IN THE 12Z TAF. MVFR CIGS ~015
025 COMMON THRU PERIOD. REDUCED VISIBILITY DUE TO HEAVY RAINFALL
LIKELY AS STRONG STORMS ARRIVE WITH FRONT. CONDITIONS MAY FALL TO
IFR AT TIMES - 20% CHANCE OF A THUNDERSTORM FROM 08Z TO 15Z TUE.
THERE IS A 70-80% CHANCE OF AN EAST WIND COMPONENT REACHING 7-8
KNOTS THRU 18Z MONDAY.
KBUR...LOW TO MODERATE CONFIDENCE IN 12Z TAF. REDUCED VISIBILITY
DUE TO HEAVY RAINFALL LIKELY AS STRONG STORMS ARRIVE WITH FRONT.
CONDITIONS MAY FALL TO IFR AT TIMES FROM 06Z TO 15Z TUESDAY.
20% CHANCE OF A THUNDERSTORM DURING THIS TIMEFRAME.
MARINE
13/154 AM.
MONDAY AFTERNOON THROUGH TUESDAY AFTERNOON, A STORM SYSTEM AND
ASSOCIATED COLD FRONT WILL MOVE ACROSS THE REGION. THIS WILL BRING
A 20-40% CHANCE OF THUNDERSTORMS ACROSS ALL THE COASTAL WATERS
DURING THAT TIMEFRAME.
SMALL CRAFT ADVISORY (SCA) LEVEL WINDS AND SEAS WILL CONTINUE
ACROSS THE OUTER WATERS THROUGH MONDAY MORNING. SCA WINDS COULD
LINGER INTO THE EARLY AFTERNOON HOURS ACROSS PZZ676. INCREASING
SOUTH TO SOUTHWEST WINDS ARE THEN EXPECTED TO PICK UP MONDAY
AFTERNOON AS THE COLD FRONT APPROACHES FROM THE NORTH. STRONG SCA
WINDS ARE EXPECTED ALONG WITH THE FRONT, THEN DECREASING FROM THE
WEST BEHIND THE FRONT TUESDAY AND TUESDAY NIGHT. WEDNESDAY THROUGH
THURSDAY INCREASING NW WINDS WILL LIKELY REACH SCA LEVELS ONCE
AGAIN. BEST CHANCES SOUTH OF POINT CONCEPTION.
FOR THE INNER WATERS SOUTH OF POINT CONCEPTION, ISOLATED GUSTS TO
21 KTS ARE POSSIBLE NEAR POINT DUME & ACROSS THE SAN PEDRO CHANNEL
MONDAY MORNING. MONDAY NIGHT AND TUESDAY INCREASING S TO SW WINDS
TO SCA LEVELS ARE EXPECTED ACROSS THE AREA AS THE FRONT APPROACHES.
ANY THUNDERSTORM THAT FORMS MAY BE CAPABLE OF FREQUENT CLOUD TO
SURFACE LIGHTNING, GUSTY AND ERRATIC WINDS, SMALL HAIL, AND EVEN A
WATERSPOUT. ADDITIONALLY, WIDESPREAD SCA LEVEL SW WINDS AND SEAS,
WITH A MODERATE CHANCE OF GALES BETWEEN MONDAY NIGHT AND TUESDAY
NIGHT DUE TO THE AFOREMENTIONED STORM.
LOX WATCHES/WARNINGS/ADVISORIES
CA...FLOOD WATCH REMAINS IN EFFECT FROM THIS EVENING THROUGH
TUESDAY AFTERNOON FOR ZONES
38-88-342-344-345-348-353-355-358-362-368>375-377>380-548. (SEE LAXFFALOX).
WIND ADVISORY IN EFFECT FROM NOON TODAY TO 10 PM PDT THIS
EVENING FOR ZONES 381>383. (SEE LAXNPWLOX).
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 9 AM PDT THIS MORNING
FOR ZONES 645-670. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL 10 AM PDT THIS MORNING
FOR ZONE 673. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL NOON PDT TODAY FOR ZONE
676. (SEE LAXMWWLOX).
PUBLIC...HALL
AVIATION...BLACK
MARINE...BLACK/CILIBERTI
SYNOPSIS...HALL
WEATHER.GOV/LOSANGELES
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