443
FXUS66 KLOX 210421
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
921 PM PDT SAT JUN 20 2026
SYNOPSIS
20/229 PM.
BELOW NORMAL TEMPERATURES WILL CONTINUE THROUGH THE WEEKEND, WITH
A DEEP MARINE LAYER, AS WELL AS GUSTY WINDS OVER THE INTERIOR. A
SIGNIFICANT WARMING TREND WILL START MONDAY AND PEAK AROUND
WEDNESDAY. A PUSH OF MOISTURE MIDWEEK WILL BRING AT LEAST A LOW
CHANCE FOR RAIN.
SHORT TERM (SAT-TUE)
20/905 PM.
***UPDATE***
MARINE LAYER CLOUDS WERE FAIRLY WIDESPREAD FOR MANY AREAS THIS
MORNING, ESPECIALLY NORTH OF POINT CONCEPTION. HOWEVER, GOOD
CLEARING ALLOWED FOR A WARMING TREND TODAY WITH HIGH TEMPERATURES
IN THE 70S TO 80S FOR MUCH OF THE REGION. LOWER CONFIDENCE IN THE
COVERAGE OF MARINE LAYER CLOUDS TONIGHT, AND IN GENERAL THINKING
THE BEST CHANCE FOR MARINE LAYER CLOUDS WILL BE NORTH OF POINT
CONCEPTION. HOWEVER, A DECENT INVERSION STILL EXISTS, AND EDDY
CIRCULATIONS IN THE SANTA BARBARA CHANNEL AND SOUTH OF THE
CHANNEL ISLANDS COULD HELP BOLSTER CLOUD DEVELOPMENT. THINGS STILL
LOOK ON TRACK FOR WARMING INTO THIS COMING WEEK AS HIGH PRESSURE
BUILDS. CURRENT FORECAST LOOKS ON TRACK IN GENERAL, BUT DECREASED
THE COVERAGE OF MARINE LAYER CLOUDS AND FOG SLIGHTLY.
***FROM PREVIOUS DISCUSSION***
MODELS ARE IN GOOD AGREEMENT SHOWING ZONAL FLOW OVER THE AREA
THROUGH THIS WEEKEND BEFORE A BUILDING STRONG HIGH PRESSURE TO THE
EAST-SOUTHEAST OVER THE DESERT SOUTHWEST STARTS NUDGING INTO THE
AREA DURING THE START OF THE COMING WORKWEEK.
MODERATE TO STRONG ONSHORE FLOW IS FORECAST TO CONTINUE THROUGH
THE SHORT TERM, THROUGH THE TRANSITION FROM ZONAL FLOW TO
ANTICYCLONIC FLOW. HOWEVER, A SLIGHT LOWERING TREND OF THE MARINE
LAYER DEPTH IS ANTICIPATED AS ONSHORE PRESSURE GRADIENTS ARE
FORECAST TO SLOWLY WEAKEN. THERE WERE NOTABLY LESS MARINE LAYER
STRATUS THIS MORNING SOUTH OF POINT CONCEPTION, WHERE A NOTICEABLE
N-NW WIND IN THE CLOUD MOTIONS WAS PRESENT. HI-RES GUIDANCE
INDICATES SIMILAR CONDITIONS CAN BE EXPECTED AGAIN SUNDAY AND
MONDAY, BUT WITH THE WEAKENING ONSHORE FLOW, THE MARINE STRATUS
SHOULD EXHIBIT A DECREASE IN AREAL EXTENT TONIGHT THROUGH AT LEAST
MONDAY. OTHER THAN THE MARINE LAYER STRATUS, SKIES SHOULD REMAIN
MOSTLY CLEAR THROUGH MONDAY.
AS FOR TEMPERATURES TODAY, MIDDAY TEMPERATURES WERE RUNNING 5-10
DEGREES WARMER THAN THE SAME TIME YESTERDAY FOR MANY AREAS,
LARGELY DUE TO LESS MORNING STRATUS COVERAGE AND QUICKER
CLEARING. OVERALL THOUGH, HIGHS THIS AFTERNOON SHOULD BE WITHIN A
FEW DEGREES OF YESTERDAY. FOR SUNDAY, ALL AREAS WILL SEE A FEW
DEGREES OF WARMING, ESPECIALLY AWAY FROM THE COAST. THE AREA-WIDE
WARMING TREND WILL CONTINUE MONDAY AND TUESDAY, AS THE RIDGE
NOSES IN, WITH COASTAL TEMPERATURES IN THE 70S AND INLAND AREAS
TOPPING OUT IN THE 80S AND 90S.
AS FOR WINDS, THE STRONG ONSHORE PRESSURE GRADIENTS WILL CONTINUE
TO GENERATE GUSTY SOUTHWESTERLY WINDS ACROSS INTERIOR SECTIONS IN
THE AFTERNOON AND EVENING HOURS. HOWEVER, AT THIS TIME, EXPECT ANY
ADVISORY-LEVEL GUSTS TO REMAIN LOCALIZED IN THE ANTELOPE VALLEY
FOOTHILLS. SO, NO WIND PRODUCTS ARE EXPECTED AT THIS TIME.
LONG TERM (WED-SAT)
20/228 PM.
FOR THE EXTENDED, MODELS CONTINUE TO EXHIBIT GOOD SYNOPTIC
AGREEMENT. AT UPPER LEVELS, HIGH PRESSURE, OVER ARIZONA AND NEW
MEXICO, PEAKS IN STRENGTH ON TUESDAY THEN GRADUALLY WEAKENS
WEDNESDAY THROUGH FRIDAY. AT THE SURFACE, MODERATE TO STRONG
ONSHORE PRESSURE GRADIENTS WILL CONTINUE WITH SOME CONTINUED WEAK
NORTHERLY OFFSHORE GRADIENTS.
FORECAST-WISE, MAIN CONCERN IN THE EXTENDED WILL BE THE HEAT. WITH
H5 HEIGHTS PEAKING TUESDAY AND 925MB TEMPS PEAKING WEDNESDAY, THE
WARMEST TEMPERATURES IN THE FORECAST ARE EXPECTED TO BE ON TUESDAY
AND WEDNESDAY, WITH GUIDANCE STILL CONTINUING THE HEAT THROUGH
THURSDAY. HIGH TEMPERATURES TUESDAY THROUGH THURSDAY ARE FORECAST
AROUND 3-6 DEGREES ABOVE SEASONAL NORMALS FOR COASTAL AREAS AND
5-10 DEGREES ABOVE NORMAL FOR VALLEYS/INTERIOR SECTIONS. FOR
WEDNESDAY, THERE WILL ALSO BE AN INCREASE IN MID-LEVEL MOISTURE
WHICH MAY ADD TO THE HEAT IMPACT AND STRESS. A GRADUAL COOLING
TREND IS LIKELY TO BEGIN ON THURSDAY OR FRIDAY. WIDESPREAD MINOR
AND AREAS OF MODERATE HEAT RISK IS EXPECTED WITH THE FORECAST
TEMPERATURES MIDWEEK WITH A SLIGHT IMPROVEMENT INTO THE END OF THE
WEEK. GIVEN THE INFLUX OF VISITORS TO THE AREA AND PLENTY OF
OUTDOOR ACTIVITIES, WILL CONTINUE WITH THE EXTREME HEAT WATCH FOR
THE LOS ANGELES COUNTY VALLEYS AND MOUNTAINS.
SECONDARY CONCERN FOR THE EXTENDED FORECAST WILL BE THE POTENTIAL
FOR SOME PRECIPITATION ON WEDNESDAY. ENSEMBLES INDICATE
INCREASING PWATS (100-150% OF NORMAL) MOVING INTO THE AREA ON
WEDNESDAY, WITH HIGH CHANCES OF PWATS GREATER THAN 1.00 INCH.
HOWEVER, MOST OF THIS MOISTURE LOOKS TO BE CONFINED TO 700 MB AND
ABOVE AND THE BEST MOISTURE MAY STAY JUST EAST AND SOUTHEAST OF
THE AREA. SO, AT THIS TIME, THERE IS A 5-15% CHANCE OF
SHOWERS/HIGH BASED THUNDERSTORMS ON WEDNESDAY JUST ABOUT ANYWHERE,
BUT WITH BEST CHANCES OVER THE HIGHER TERRAIN. THIS WILL NEED TO
BE MONITORED CLOSELY OVER THE COMING DAYS.
AVIATION
21/0410Z.
AT 0400Z AT KLAX, THE MARINE LAYER WAS 1200 FEET DEEP. THE TOP
OF THE INVERSION WAS 5000 FEET WITH A TEMPERATURE OF 19 DEGREES
CELSIUS.
FOR THE 06Z TAF PACKAGE, HIGH CONFIDENCE IN KSBA, KBUR, KVNY, KPMD
AND KWJF.
FOR ALL OTHER SITES, LOW TO MODERATE CONFIDENCE IN 06Z TAF. THERE
IS A 40-50% CHANCE THAT CIG RESTRICTIONS DO NOT DEVELOP OVERNIGHT.
ADDITIONALLY, IF CIGS DO DEVELOP, EQUAL CHANCES OF IFR OR MVFR
LEVELS.
KLAX...LOW CONFIDENCE IN 06Z TAF. THERE IS A 40% CHANCE THAT CIGS
DO NOT DEVELOP SUNDAY MORNING. IF CIGS DO DEVELOP, THERE ARE EQUAL
CHANCES OF IFR OR MVFR CIGS. NO SIGNIFICANT EASTERLY WIND
COMPONENT IS EXPECTED.
KBUR...HIGH CONFIDENCE IN 06Z TAF AS CAVU CONDITIONS ARE EXPECTED
THROUGH THE PERIOD.
MARINE
20/914 PM.
HIGH CONFIDENCE IN THE WINDS AND SEAS REMAINING BELOW SMALL CRAFT
ADVISORY (SCA) CRITERIA INTO THE MIDDLE OF THE WEEK. LOCALIZED
GUSTY WINDS UP TO 25 KTS ARE POSSIBLE IN THE WESTERN SANTA BARBARA
CHANNEL TONIGHT. THE TYPICALLY GUSTY WINDS OF 15 TO 20 KTS ARE
EXPECTED EACH AFTERNOON AND EVENING OVER PORTIONS OF THE WATERS
SUNDAY AND MONDAY, MAINLY BETWEEN POINT CONCEPTION TO SAN NICOLAS
ISLAND AND INTO THE WESTERN SBA CHANNEL. THERE IS A 40% CHANCE
THEY BECOME WIDESPREAD ENOUGH TO WARRANT A SCA.
LOX WATCHES/WARNINGS/ADVISORIES
CA...EXTREME HEAT WATCH IN EFFECT FROM TUESDAY MORNING THROUGH
THURSDAY EVENING FOR ZONES 88-368-372-373-379-380-548. (SEE LAXNPWLOX).
PZ...NONE.
PUBLIC...PHILLIPS/THOMPSON/SB
AVIATION...RAT
MARINE...BATZ/CILIBERTI
SYNOPSIS...RK
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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