146
FXUS66 KLOX 131718
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1018 AM PDT SAT SEP 13 2025
SYNOPSIS
13/927 AM.
A WARMING TREND WILL CONTINUE, WITH TEMPERATURES INCREASING A
COUPLE DEGREES FROM DAY TO DAY THROUGH NEXT WEEK. NIGHT THROUGH
MORNING LOW CLOUDS AND FOG COVER MANY COASTS AND COASTAL VALLEYS
THROUGH NEXT WEEK, AND SOME OF THE FOG COULD BECOME DENSE. THE
HEAT PEAKS DURING THE MIDDLE OF NEXT WEEK, AND WILL BE REPLACED BY
A SLOW COOLING TREND AND CHANCES FOR SHOWERS AND THUNDERSTORMS BY
THE END OF NEXT WEEK.
SHORT TERM (TDY-MON)
13/933 AM.
***UPDATE***
ANOTHER SLOW WEATHER DAY LOCALLY WITH TEMPERATURES STILL 4-8
DEGREES BELOW NORMAL INLAND BUT NEAR NORMAL AT THE COAST. NO BIG
CHANGES EXPECTED FROM THE PREVIOUS FORECAST AS THE LATEST MODELS
ARE MORE OR LESS SINGING THE SAME TUNE, WHICH IS A SLOW WARMING
TREND INTO NEXT WEEK LEADING TO TEMPERATURES GETTING BACK TO NEAR
NORMAL BY AROUND TUESDAY.
***FROM PREVIOUS DISCUSSION***
AN UPPER-LEVEL RIDGE WILL CONTINUE AMPLIFYING OVER THE LOCAL AREA
TODAY AND PERSIST THROUGH THE REMAINDER OF THIS WEEKEND INTO
NEXT WEEK. THIS WILL PROLONG THE WARMING TREND. HIGH TEMPERATURES
THIS AFTERNOON WILL GAIN A COUPLE OR FEW DEGREES FROM YESTERDAY,
REACHING THE UPPER 70S TO THE 80S IN MOST PLACES, COOLER AT THE
BEACHES. THE DAY-TO-DAY WARMING WILL BE MODEST, HOWEVER, AS
PERIODICALLY-REINFORCING TROUGHS OVER THE PACIFIC NORTHWEST
PREVENT MORE SUBSTANTIAL HEIGHT RISES FROM MATERIALIZING ACROSS
THE LOCAL AREA. NEVERTHELESS, GRADUALLY WEAKENING LAX-DAG ONSHORE
PRESSURE GRADIENTS BENEATH THE INITIAL BOOST IN MIDLEVEL HEIGHTS
SHOULD CORRESPOND TO HIGH TEMPERATURES RISING A COUPLE OF DEGREES
FROM DAY TO DAY. BY MONDAY, EXPECT HIGHS IN THE 80S IN MOST
PLACES, REACHING THE LOWER TO MIDDLE 90S IN THE TYPICALLY-WARMER
INTERIOR VALLEY LOCALES, BUT REMAINING IN THE 70S CLOSER TO THE
OCEAN. AND WITH THE DECREASING ONSHORE PRESSURE GRADIENTS AND
RISING MIDLEVEL HEIGHTS, MARINE STRATUS AND FOG SHOULD CLEAR MORE
QUICKLY DURING THE DIURNAL HEATING CYCLE -- PROGRESSIVELY THROUGH
THIS WEEKEND AND INTO EARLY NEXT WEEK -- BUT STILL RETURN TO THE
COASTS AND COASTAL VALLEYS EACH NIGHT. THERE WILL BE A TENDENCY
FOR FOG TO INCREASINGLY PREDOMINATE OVER LOW CLOUDS, AND THERE
WILL BE A 20% CHANCE FOR DENSE FOG ADVISORIES TO BECOME NECESSARY
DURING THE NIGHT THROUGH MORNING INTO NEXT WEEK. PRECIPITATION
WILL NOT OCCUR THROUGH THE PERIOD. WEAK SUNDOWNERS WINDS ARE
ANTICIPATED EACH LATE AFTERNOON THROUGH EARLY OVERNIGHT THIS
WEEKEND, THOUGH PEAK GUSTS ARE PRESENTLY FORECAST TO PRIMARILY
RANGE FROM 35-40 MPH.
LONG TERM (TUE-FRI)
13/110 AM.
THE WARMING TREND CONTINUES INTO THE MIDDLE PART OF NEXT WEEK,
PEAKING AROUND MID-WEEK. HEIGHTS AT 500 MB ARE FORECAST TO REACH
JUST SHORT OF 590 DAM OVER SOUTHERN CALIFORNIA ON TUESDAY AND
WEDNESDAY. AND WITH PRESSURE GRADIENTS CONTINUING TO TREND LESS
ONSHORE FROM DAY TO DAY, HIGH TEMPERATURES BY TUESDAY AND
WEDNESDAY ARE PROJECTED TO REACH WELL INTO THE 90S IN MOST PLACES
AWAY FROM THE OCEAN, WITH 98-103F READINGS OVER SOME OF THE
WARMER VALLEYS SUCH AS THE WESTERN SAN FERNANDO VALLEY. ALSO, THE
TENDENCY FOR NIGHT THROUGH MORNING FOG -- POTENTIALLY DENSE -- TO
BE FAVORED OVER LOW CLOUDS ACROSS THE COASTS AND COASTAL VALLEYS
WILL CONTINUE, AND THERE WILL BE A 20% CHANCE FOR DENSE FOG
ADVISORIES TO BE NECESSARY NEXT WEEK.
ALSO OF NOTE, MONSOONAL MOISTURE IS FORECAST TO BEGIN TO RE-ENTER
THE AREA BY THE MIDDLE OF NEXT WEEK, WHICH COULD BOOST HEAT
INDICES AND ELEVATE OVERNIGHT LOWS (READINGS NOT FALLING MUCH
BELOW 70F IN MANY AREAS). REGARDING HEAT IMPACTS, CURRENTLY NEXT
WEDNESDAY APPEARS TO FEATURE THE HOTTEST TEMPERATURES, AND THERE
IS A 20% CHANCE FOR HEAT ADVISORIES TO BECOME NECESSARY IN SOME
AREAS ON WEDNESDAY -- GIVEN HIGH TEMPERATURES SEVERAL DEGREES
ABOVE NORMAL AWAY FROM THE COAST, INCREASED HUMIDITY, AND LIMITED
RELIEF FROM THE HEAT WITH THE ELEVATED OVERNIGHT LOW TEMPERATURES.
MEDIUM-RANGE MODEL GUIDANCE SUGGESTS THAT THE AFOREMENTIONED
MONSOONAL MOISTURE APPEARS TO COME FROM THE PHASING OF A DIFFUSE
AND SLOW-MOVING UPPER LOW OFF THE SOUTHERN CALIFORNIA COAST --
LARGELY DETACHED FROM STEERING CURRENTS ALOFT -- AND A POLEWARD
FLUX OF TROPICAL MOISTURE EAST OF THE UPPER LOW, POTENTIALLY
EMANATING FROM A REMNANT TROPICAL CYCLONE AND OTHER WAVES. THERE
ARE A LOT OF MESOSCALE FACTORS THAT WILL GREATLY INFLUENCE THE
IMPACT OF THIS MOISTURE ON LOCAL-AREA SENSIBLE WEATHER,
ESPECIALLY GIVEN THE DISTANT FORECAST-TIME RANGE. HOWEVER, AN
APPRECIABLE SUBSET OF NUMERICAL MODEL SOLUTIONS SUGGEST THAT THIS
PATTERN WILL FAVOR SHOWER AND THUNDERSTORM POTENTIAL ACROSS THE
LOCAL AREA NEXT THURSDAY THROUGH FRIDAY, DRYING OUT BY NEXT
WEEKEND. GIVEN THE WESTWARD-DISPLACED MOISTURE PLUME DIRECTED BY
THE FLOW AROUND THE OFFSHORE UPPER LOW, MODEST SHOWER AND
THUNDERSTORM CHANCES WILL BE DISTRIBUTED ACROSS MOST AREAS, AND
THERE COULD EVEN BE A NOCTURNAL COMPONENT TO THIS ACTIVITY. AND
GIVEN THE POSITION OF THE UPPER LOW OFFSHORE, EVEN FURTHER
INCREASES IN HUMIDITY AND CLOUD COVERAGE ARE CURRENTLY EXPECTED TO
YIELD A SLOW COOLING TREND BY LATE NEXT WEEK INTO NEXT WEEKEND.
OVERALL, THIS IS A LOW-CONFIDENCE FORECAST -- GIVEN LOW
PREDICTABILITY INHERENT TO SUCH SMALL-SCALE FORCING FEATURES AT
THIS DISTANT OF A FORECAST-TIME RANGE, THOUGH THUNDERSTORM IMPACTS
WILL BE POSSIBLE. INTERESTS ACROSS THE REGION ARE ENCOURAGED TO
MONITOR THE LATEST INFORMATION FROM THE NATIONAL WEATHER SERVICE
AS FORECAST DETAILS BECOME REFINED INTO NEXT WEEK.
AVIATION
13/1717Z.
AT 1600Z AT KLAX, THE MARINE LAYER WAS 2600 FT DEEP. THE TOP OF
THE INVERSION WAS AT 4800 FT WITH A TEMPERATURE OF 18 C.
HIGH CONFIDENCE IN TAFS FOR DESERT AIRFIELDS (KPMD AND KWJF).
MODERATE CONFIDENCE IN ALL COASTAL AND VALLEY TAFS.
TIMING OF CIG/VSBY RESTRICTIONS MAY BE OFF BY 2 HOURS & FLIGHT
CATEGORIES MAY BE OFF BY ONE AT TIMES WHEN CIGS ARE PRESENT.
THERE IS A CHC FOR NO LOW CLOUDS AT KPRB (30%), KBUR (15%), AND
KVNY (15%).
KLAX...MODERATE CONFIDENCE IN 18Z TAF. ARRIVAL AND CLEARING TIMES
MAY BE OFF BY +/- 3 HOURS. THERE IS A 10% CHANCE OF A SOUTHEAST
WIND COMPONENT REACHING 8 KT 10Z-17Z SUN.
KBUR...MODERATE CONFIDENCE IN 18Z TAF. ARRIVAL AND CLEARING TIMES
MAY BE OFF BY +/- 2 HOURS. HOWEVER, THERE IS A 15% CHANCE FOR NO
LOW CLOUDS TONIGHT.
MARINE
13/759 AM.
SMALL CRAFT ADVISORY (SCA) LEVEL NW WINDS (20-30 KTS) WILL IMPACT
THE OUTER WATERS AND THE NEARSHORE WATERS ALONG THE CENTRAL COAST
THROUGH LATE SUNDAY NIGHT, PEAKING IN THE AFTERNOON AND EVENING
HOURS, WITH RELATIVE LULLS EACH MORNING. THERE IS A 50% CHANCE FOR
GALE FORCE WINDS (34-38 KTS) SUNDAY AFTERNOON THROUGH EVENING FOR
THE NORTHERN OUTER WATERS BEYOND 20 NM FROM SHORE. CHANCES FOR
GALES NEARSHORE TO 20 NM AWAY FROM SHORE ARE 25%. SEAS WILL PEAK
AROUND 6 TO 8 FEET THROUGH LATE SUNDAY. CONDITION WILL REMAIN SUB-
ADVISORY MONDAY AND TUESDAY.
FOR THE INNER WATERS SOUTH OF POINT CONCEPTION, THERE IS A
MODERATE CHANCE OF SCA LEVEL WINDS (UP TO 25 KTS) ACROSS THE
WESTERN PORTION OF THE SANTA BARBARA CHANNEL DURING THE AFTERNOON
AND EVENING HOURS ON SATURDAY AND SUNDAY, BUT WINDS SHOULD STAY IN
THE WESTERN PORTION OF THE CHANNEL, THUS NO SCA WILL BE ISSUED
AT THIS POINT. SEAS WILL BE CHOPPY AND PEAK AT 3 TO 4 FEET THIS
WEEKEND. ELSEWHERE AND OTHERWISE, WINDS WILL REMAIN SUB-ADVISORY
THROUGH TUESDAY.
LOX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 9 PM PDT THIS EVENING
FOR ZONE 645. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL 3 PM PDT SUNDAY FOR ZONE
670. (SEE LAXMWWLOX).
GALE WATCH IN EFFECT FROM SUNDAY AFTERNOON THROUGH LATE
SUNDAY NIGHT FOR ZONE 670. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL 3 AM PDT MONDAY FOR
ZONES 673-676. (SEE LAXMWWLOX).
PUBLIC...MW/COHEN
AVIATION...BLACK
MARINE...LEWIS/BLACK
SYNOPSIS...MW/COHEN
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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