001
FXUS66 KLOX 201324
AFDLOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
524 AM PST MON JAN 20 2025
SYNOPSIS
20/413 AM.
SANTA ANA WINDS WILL ARRIVE THIS MORNING AND CLEAR OUT THE LOW
CLOUDS. A MODERATE TO STRONG SANTA ANA WIND EVENT WILL AFFECT
VENTURA AND LOS ANGELES COUNTIES TODAY AND TUESDAY, WITH WEAKER
OFFSHORE FLOW WEDNESDAY AND THEN ANOTHER BUMP UP IN WINDS
THURSDAY. TEMPERATURES WILL BE BELOW NORMAL TODAY AND TUESDAY,
WITH A WARMING TREND LATER IN THE WEEK. HUMIDITY LEVELS WILL BE
LOW TO VERY LOW. FROST OR FREEZING TEMPERATURES ARE LIKELY IN
WIND SHELTERED AREAS EACH NIGHT TODAY THROUGH THURSDAY. THERE IS
A DEVELOPING CHANCE OF RAIN NEXT WEEKEND.
SHORT TERM (TDY-WED)
20/439 AM.
***HIGH WIND WARNINGS ARE IN EFFECT THIS MORNING THROUGH EARLY
TUESDAY AFTERNOON FOR MOST OF VENTURA COUNTY AND LOS ANGELES
COUNTY DUE TO LIKELIHOOD WIDESPREAD DAMAGING WINDS***
***DANGEROUS FIRE WEATHER CONDITIONS EXPECTED FOR MUCH OF VENTURA
AND LOS ANGELES COUNTIES THIS MORNING THROUGH TUESDAY EVENING
POSSIBLY CONTINUING THROUGH THURSDAY***
THE LATEST IN A SEEMINGLY ENDLESS SERIES OF SANTA ANA WIND EVENTS
WAS BEGINNING TO UNFOLD ACROSS THE REGION EARLY THIS MORNING. A
STRONG VORT MAX WAS DROPPING SOUTHWARD THROUGH NEVADA INTO EASTERN
CA THIS MORNING, AND THIS WILL HELP TO CARVE A TROUGH JUST TO THE
EAST OF THE REGION TODAY. UPPER LEVEL WINDS WILL BECOME NORTHERLY
AND INCREASE SHARPLY THIS MORNING.
WEST OF THE MOUNTAINS, A 3000 FOOT DEEP MARINE LAYER CAUSED CLOUDS
TO BECOME ENTRENCHED IN COASTAL AND VALLEY AREAS LAST EVENING,
WITH CLOUDS ALL THE WAY TO THE COASTAL SLOPES. DURING THE LAST
HOUR OR TWO, SATELLITE IMAGERY HAS BEGUN TO SHOW SOME EROSION OF
THE STRATUS FIELD IN THE FOOTHILLS AND INTERIOR VALLEYS. WHILE N-S
PRESSURE GRADIENTS HAVE REMAINED WEAKLY OFFSHORE OVER THE PAST TWO
DAYS, W-E GRADIENTS BETWEEN KLAX AND KDAG, WHICH WERE ONSHORE ON
SUN HAVE NOW FLIPPED WEAKLY OFFSHORE. GRADIENTS SHOULD BECOME
INCREASINGLY OFFSHORE TODAY, AS A VERY STRONG AND COLD SURFACE
HIGH PRESSURE SYSTEM BEGINS TO PUSH INTO THE GREAT BASIN.
STRONG SUBSIDENCE AND SIGNIFICANT COLD AIR ADVECTION WILL
OVERSPREAD THE REGION FROM TO NORTH AND EAST TODAY AS THE
TROUGH AXIS AND VORT ENERGY DROP SOUTHWARD JUST EAST OF THE
REGION. THIS WILL FORCE WINDS INTO LOWER LEVELS OF THE
ATMOSPHERE THIS MORNING, CAUSING LOW CLOUDS TO DISAPPEAR RAPIDLY,
AND ALLOWING STRONG NORTH TO NORTHEAST WINDS TO PUSH INTO L.A. AND
VTU COUNTIES WEST OF THE MOUNTAINS.
WINDS AT 850 MB AND 700 MB WINDS WILL INCREASE TO BETWEEN 50 AND
60 KNOTS LATER TODAY, THEN MAY BECOME A BIT STRONGER EARLY
TONIGHT. TEMPERATURES AT 850 MB WILL DROP FROM 4 C TO 0 C ACROSS
THE ANTELOPE VALLEY TODAY, THEN DOWN TO -5 C TONIGHT. THIS WILL
SET UP A VERY SHARP THERMAL GRADIENT OVER THE SAN GABRIEL
MOUNTAINS, WITH A 15 DEGREE C TEMPERATURE DIFFERENCE IN 25 MILES
OR SO BY LATE TONIGHT. OFFSHORE PRESSURE GRADIENTS WILL INCREASE
DURING THE DAY TODAY (GOING AGAINST TYPICAL DIURNAL TRENDS) INTO
TONIGHT, PEAKING IN THE -8 TO -10 MB RANGE BY EARLY TUE MORNING.
WINDS ARE EXPECTED TO INCREASE QUICKLY IN THE MOUNTAINS OF L.A.
AND VTU COUNTIES BEFORE SUNRISE, THEN OVERSPREAD THE VALLEYS
AROUND DAYBREAK, AND THE PUSH ACROSS COASTAL PLAIN LATER THIS
MORNING. WINDS ARE EXPECTED TO PEAK THIS AFTERNOON OR EARLY
TONIGHT, THEN REMAIN STRONG OVERNIGHT AND EARLY TUE, WINDS WILL
SLOWLY DIMINISH TUE AFTERNOON. MAX GUSTS ACROSS MANY WIND PRONE
COASTS AND VALLEYS WILL AVERAGE 50 TO 70 MPH. THE HIGHEST GUSTS
WILL LIKELY BE FOCUSED NEAR SANTA CLARITA VALLEY AND NEAR THE
HIGHWAY 118/126 CORRIDORS, AFFECTING CITIES INCLUDING SIMI VALLEY,
MOORPARK, PORTER RANCH, AND SANTA PAULA.
IN ADDITION, WITH THE STRONG UPPER LEVEL WIND SUPPORT EXTENDING
WELL UP TO 700 MB LEVEL, THERE IS POTENTIAL FOR LOCALLY
STRONG/DAMAGING MOUNTAIN WAVE WIND ACTIVITY ACROSS THE FOOTHILLS
OF THE SAN GABRIEL AND SAN FERNANDO VALLEYS, MAINLY FOCUSED NEAR
THE HIGHWAY 210/118 CORRIDORS FROM PORTER RANCH TO SAN FERNANDO,
EASTWARD TO LA CRESCENTA/ALTADENA, EXTENDING TO AZUSA/GLENDORA
AND MONROVIA. THE HIGHEST PROBABILITY OF ANY STRONGER MOUNTAIN
WAVE WIND ACTIVITY WOULD MOST LIKELY BE FROM 2 PM THIS
AFTERNOON TO 2 AM TUESDAY.
IN THE MOUNTAINS, MAX GUSTS WILL LIKELY AVERAGE 60 TO 80 MPH,
WITH ISOLATED GUSTS IN THE 80 TO 100 MPH RANGE POSSIBLE IN THE
MOST FAVORED MOUNTAIN LOCATIONS (MOST LIKELY IN THE SAN GABRIELS
AND SANTA SUSANAS).
WHILE OFFSHORE WINDS WILL LIKELY PEAK IN MANY AREAS LATE
THIS AFTERNOON INTO TONIGHT WHEN THERE IS THE STRONGEST UPPER
LEVEL WIND SUPPORT. HOWEVER, STRONG OFFSHORE WINDS WILL LIKELY
CONTINUE IN MANY AREAS INTO TUESDAY MORNING DUE TO THE STRONG
OFFSHORE PRESSURE GRADIENTS AND CONTINUED COLD AIR ADVECTION.
WHILE THE OFFSHORE WINDS WILL LIKELY DIMINISH SOME BY TUESDAY
AFTERNOON, THERE WILL LIKELY CONTINUE TO BE A LONG DURATION OF
CRITICAL RED FLAG FIRE WEATHER CONDITIONS ACROSS MUCH OF
LA/VENTURA COUNTIES POTENTIALLY PERSISTING INTO THURSDAY DUE TO
THE LONG DURATION OF OFFSHORE WINDS COMBINING WITH WIDESPREAD
SINGLE DIGIT HUMIDITIES. IN FACT, THIS WILL LIKELY BE THE DRIEST
AIR MASS WE HAVE SEEN WITH ALL OFFSHORE WIND EVENTS THIS SEASON,
WITH MANY AREAS SEEING HUMIDITIES FALL TO BETWEEN 2 AND 5 PERCENT
TUESDAY THROUGH THURSDAY.
THESE STRONG OFFSHORE WINDS WILL BRING HAZARDOUS WINDS AND
DANGEROUS WIND WAVES TO CATALINA ISLAND, AVALON HARBOR AS WELL
AS THE CHANNEL ISLANDS. FOR ALL OF THE DETAILS ON THE WINDS AND
MARINE HAZARDS, PLEASE SEE THE LAXNPWLOX AND LAXCFWLOX PRODUCTS.
LIKE MOST SANTA ANAS, THERE WILL BE SOME COOLING TODAY ACROSS THE
INTERIOR DUE TO COOL AIR ADVECTION WHILE THE COASTS AND VLYS SEE
SOME WARMING DUE TO THE THE COMPRESSIONAL WARMING. MOST AREAS ARE
EXPECTED TO WARM ON TUESDAY.
GUSTY NE WINDS WILL LIKELY CONTINUE TUE NIGHT INTO WED, AND WIND
ADVISORIES MAY BE NEEDED FOR SOME AREAS. RISING HEIGHTS AND
WARMING AT 850/950 MB SHOULD LEAD TO WARMING IN MOST AREAS WED,
WITH MAX TEMPS APPROACHING 80 DEGREES IN THE WARMEST LOCATIONS.
WITH CLEAR SKIES AND VERY LOW HUMIDITY VALUES, IT WILL BECOME VERY
COLD IN WIND SHELTERED AREAS TONIGHT AND ESPECIALLY TUE NIGHT.
LOWS WILL DROP TO BETWEEN 10 AND 15 DEGREES IN THE ANTELOPE
VALLEY, AND INTO THE LOWER TO MID 20S IN INTERIOR PORTIONS OF THE
SLO VALLEYS AND THE CUYAMA VALLEY. FREEZING TEMPERATURES ARE
POSSIBLE EACH NIGHT IN WIND-SHELTERED PORTIONS OF COASTAL SLO AND
SBA COUNTIES. FREEZES ARE POSSIBLE IN THE COLDER VALLEYS OF L.A.
AND VTU COUNTY, ESPECIALLY TUE NIGHT WHEN THERE IS LESS WIND.
LONG TERM (THU-SUN)
20/523 AM.
THERE WILL BE ANOTHER BUMP UP IN OFFSHORE GRADIENTS WED NIGHT AND
THU. THOUGH UPPER SUPPORT WILL NOT BE SIGNIFICANT, GRADIENTS WILL
BE STEEP, WITH WIDESPREAD ADVISORY LEVEL WINDS LIKELY IN MOST OF
VENTURA COUNTY, IN THE MOUNTAINS OF L.A. COUNTY INCLUDING THE
SANTA MONICAS, AND IN THE NORTHERN AND WESTERN L.A. COUNTY
VALLEYS. WINDS COULD EVEN APPROACH HIGH WIND WARNING LEVELS
IN SOME AREAS.
HEIGHTS WILL RISE WED NIGHT AND THU AS A STRONG UPPER LEVEL HIGH
BUILDS INTO CA. MAX TEMPS WILL BE UP A FEW MORE DEGREES THU, WITH
HIGHS LIKELY RISING INTO AT LEAST THE LOWER 80S IN THE WARMEST
VALLEY AND INTERIOR COASTAL SECTIONS OF L.A. AND VTU COUNTIES.
THE UPPER HIGH WILL BREAK DOWN AND MOVE EAST ON FRIDAY. THERE
WILL BE ENOUGH OFFSHORE FLOW IN THE MORNING TO KEEP SKIES FREE OF
LOW CLOUDS, BUT HIGH CLOUDS WILL INCREASE DURING THE DAY AHEAD ON
AN UPPER LOW. THERE WILL BE A BIG SWITCH TO ONSHORE FLOW IN THE
AFTERNOON AND THIS WILL LEAD TO A BIG 4 TO 8 DEGREE COOL DOWN.
THINGS START TO GET INTERESTING FOR THE WEEKEND. THERE IS NOT
GREAT MDL OR ENSEMBLE AGREEMENT SO EXACT CONFIDENCE IN LOW BUT THE
GENERAL 48 HOUR CONFIDENCE HAS GROWN QUITE A BIT. THERE WILL BE A
COMPACT UPPER LOW OFF THE COAST AND A COLD POS TILT RETROGRADING
TROF MOVING OUT OF THE GREAT BASIN AND INTO THE STATE. AT SOME
POINT THESE TWO FEATURES WILL MERGE INTO ONE UPPER LOW. THE EXACT
PHASING, TIMING AND LOCATION OF THIS SYSTEM IS STILL VERY MUCH UP
IN THE AIR.
LOOKING AT THE ENTIRE 48 HOUR PERIOD...THERE IS A 60 TO 70 PERCENT
CHC OF RAIN SOMETIME DURING THIS PERIOD. ABOUT 40 PERCENT OF THE
ENSEMBLES SHOW RAINFALL AMOUNTS OF OVER HALF AN INCH FOR MOST
COAST AND VLYS. THIS COULD ALSO BE A SIGNIFICANT MTN SNOW EVENT
WITH SNOW LEVELS AT OR EVEN UNDER 4000 FT. ONCE LAST DETAIL IS
THAT THE MOST LIKELY (40 PERCENT) SET UP WOULD ALLOW FOR AN
ENHANCED CONVECTIVE POTENTIAL WITH DIFLUENT FLOW ALOFT AND -25
DEGREE C 500MB. EARLY ESTIMATES CALL FOR A 25 PERCENT CHC OF A
TSTM DURING THIS PERIOD.
PLEASE NOTE THE OFFICIAL FORECAST IS DICED INTO 6 HOUR BLOCKS AND
THE CHANCE OF RAIN IN EACH 6 HOUR PERIOD IS MUCH LESS AND THE CHC
OF A TSTM IS BELOW 15 PERCENT IN ANY ONE PERIOD WHICH TO LOW TO
MENTION IN THE FORECAST.
THIS WEEKEND SYSTEM IS EVOLVING AND HOPEFULLY WILL BE REFINED OVER
THE NEXT FEW DAYS.
AVIATION
20/1207Z.
AT 07Z AT KLAX, THE MARINE LAYER WAS 2800 FT DEEP. THE TOP OF THE
INVERSION WAS AT 4500 FT WITH A TEMPERATURE OF 9C.
OVERALL, MODERATE CONFIDENCE IN 12Z TAF PACKAGE. TIMING OF
CIGS/VSBY RESTRICTIONS MAY BE OFF +/- 2 HOURS. FLIGHT CATS COULD
BE OFF ONE OR TWO ESPECIALLY DURING WORST CONDITIONS. AFTER 18Z
MON, VFR CONDS ARE EXPECTED FOR AIRFIELDS. HOWEVER, LLWS AND
TURBULENCE WILL THEN BECOME PROBLEMATIC FOR AIRFIELDS ESPECIALLY
ACROSS LA/VTA COUNTIES. TIMING OF WIND SHIFT CHANGES MAY BE OFF A
COUPLE HOURS, AND WIND GUSTS COULD BE OFF 10-15 KTS.
KLAX...MODERATE CONFIDENCE IN 12Z TAF. THERE IS A 30% CHANCE OF
EAST WIND COMPONENT OF 6-8 KTS BEFORE 22Z MON, WITH AN INCREASE TO
70% + UNTIL 09Z TUE.
KBUR...MODERATE CONFIDENCE IN 12Z TAF. INCREASING NORTHEAST WINDS
BY MONDAY LATE MORNING INTO AFTERNOON. THERE IS A 30% CHANCE OF
BRIEF GUSTS OF 40+ KNOTS BY LATE MONDAY AFTERNOON. LGT-MDT TURBC
IS POSSIBLE TO LIKELY AFTER 16Z.
MARINE
20/138 AM.
FOR THE OUTER WATERS, SMALL CRAFT ADVISORY (SCA) LEVEL WINDS ARE
EXPECTED TO CONTINUE THRU MONDAY MORNING. THESE CONDITIONS ARE
FAVORED FROM POINT CONCEPTION TO SAN NICOLAS ISLAND WHICH
INCLUDES THE WATERS AROUND AND TO THE WEST OF THE CHANNEL ISLANDS
(PZZ676/673). THERE IS A 40-60% CHANCE OF GALE FORCE LEVEL NE
WINDS FOR THE WATERS AROUND AND TO THE SOUTH OF THE CHANNEL
ISLANDS (PZZ673 AND PZZ676) MONDAY AFTERNOON THRU TUESDAY MORNING,
WITH A 20% CHANCE OF GALES LINGERING INTO THE AFTERNOON.
OTHERWISE, SUB-ADVISORY CONDS ARE EXPECTED THRU THURSDAY NIGHT.
FOR THE INNER WATERS NORTH OF PT SAL (PZZ645), THERE IS A 10-20%
CHANCE OF SCA LEVEL WIND GUSTS MON EVENING AND TUESDAY MORNING.
OTHERWISE, SUB-ADVISORY CONDS ARE EXPECTED THRU LATE IN THE WEEK.
FOR THE INNER WATERS SOUTH OF POINT CONCEPTION, FROM VENTURA
HARBOR TO MALIBU AND OUT PAST THE CHANNEL ISLANDS, THERE IS A
80-90% CHANCE OF GALE FORCE E/NE WIND GUSTS THROUGH EARLY TUESDAY
AFTERNOON. FOR THE NEARSHORE WATERS FROM CHANNEL ISLANDS HARBOR TO
MALIBU AND OUT TO SANTA CRUZ ISLAND, THERE IS A 50-60% CHANCE OF
STORM FORCE WIND GUSTS MONDAY AFTERNOON INTO TUESDAY MORNING. FROM
THE ORANGE COUNTY SHORES THROUGH THE SAN PEDRO CHANNEL, THERE IS
A 60-80% CHANCE OF GALE FORCE WIND GUSTS MONDAY EVENING THROUGH
TUESDAY MORNING, WITH A 80% CHANCE OF 25-35 KT WINDS IMPACTING
AVALON HARBOR. STEEP, CHOPPY SEAS OF 5 TO 8 FEET WILL BE POSSIBLE
DURING THIS TIME FRAME.
BREEZY OFFSHORE WINDS MAY CONTINUE AT TIMES FOR THE INNER WATERS
THROUGH THURSDAY OR FRIDAY.
LOX WATCHES/WARNINGS/ADVISORIES
CA...HIGH SURF WARNING IN EFFECT UNTIL 2 PM PST TUESDAY FOR ZONE
87. (SEE LAXCFWLOX).
COASTAL FLOOD ADVISORY IN EFFECT UNTIL 2 PM PST TUESDAY FOR
ZONE 87. (SEE LAXCFWLOX).
WIND ADVISORY REMAINS IN EFFECT UNTIL 2 PM PST TUESDAY FOR
ZONES 87-367-370-381>383-548. (SEE LAXNPWLOX).
HIGH WIND WARNING REMAINS IN EFFECT UNTIL 2 PM PST TUESDAY
FOR ZONES 88-354-355-358-362-369-371>380-549-550. (SEE LAXNPWLOX).
RED FLAG WARNING IN EFFECT UNTIL 10 PM PST TUESDAY FOR ZONES
288-354-355-358-362-369-371>380-548. (SEE LAXRFWLOX).
FIRE WEATHER WATCH IN EFFECT FROM TUESDAY EVENING THROUGH
THURSDAY EVENING FOR ZONES 288-354-355-358-362-369>380. (SEE LAXRFWLOX).
RED FLAG WARNING IN EFFECT UNTIL 2 PM PST TUESDAY FOR ZONES
367-370-381-382. (SEE LAXRFWLOX).
PZ...GALE WARNING IN EFFECT FROM NOON TODAY TO 2 PM PST TUESDAY
FOR ZONES 650-655-676. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM PST THIS MORNING
FOR ZONES 673-676. (SEE LAXMWWLOX).
PUBLIC...DB/RORKE/DB
AVIATION...BLACK
MARINE...SMITH/BLACK/RM
SYNOPSIS...DB/RM/DMB
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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