687
FXUS66 KLOX 170603
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1003 PM PST THU JAN 16 2025
SYNOPSIS
16/809 PM.
COOLER TEMPERATURES ARE EXPECTED THROUGH THE WEEKEND AS ONSHORE
FLOW RETURNS. MORNING LOW CLOUDS AND FOG ARE POSSIBLE ACROSS
COAST AND VALLEY AREAS FRIDAY AND SATURDAY MORNINGS. ANOTHER SANTA
ANA WIND EVENT WILL BE POSSIBLE LATER MONDAY INTO TUESDAY. MUCH
BELOW NORMAL DAYTIME AND NIGHTTIME TEMPERATURES WILL CONTINUE
THROUGH THIS WEEK AND MOST OF NEXT WEEK.
SHORT TERM (THU-SUN)
16/953 PM.
***UPDATE***
TEMPERATURES TRENDED COOLER TODAY WITH WEAKENING OFFSHORE WINDS,
AND WESTERLY WINDS RETURNING IN THE LATE AFTERNOON. HIGHS STILL
TRENDED 4-7 DEGREES ABOVE NORMAL FOR INTERIOR VENTURA COUNTY AND
NORTH INTO SANTA BARBARA AND SAN LUIS OBISPO COUNTIES WITH
TEMPERATURES IN THE 60S TO LOW 70S. TONIGHT, CONFIDENCE IS ON THE
LOWER SIDE, AS GUIDANCE SUGGESTS THE RETURN OF MARINE LAYER CLOUDS
TO COASTS AND VALLEYS. CURRENT SATELLITE IMAGERY ONLY SHOWS A FEW
AREAS (SOUTH OF ORANGE COUNTY AND OFF THE SAN LUIS OBISPO COUNTY
COAST) WHERE LOW CLOUDS ARE BEGINNING TO DEVELOP. THIS MAY BE DUE
TO THE LACK OF AN INVERSION, BUT BUILDING HIGH PRESSURE SHOULD
HELP TO DEVELOP ONE OVERNIGHT. WITH THE CLEAR SKIES, LINGERING
DRY AIR AND LIGHT WINDS, TEMPERATURES WILL BE CHILLY TONIGHT.
CURRENT FROST AND FREEZE PRODUCTS LOOK ON TRACK. TEMPERATURES
COULD TREND 5-7 DEGREES COLDER IN AREAS THAT FAIL TO SEE MARINE
LAYER CLOUDS. HIGH PRESSURE BUILDS INTO THE AREA THROUGH THE
WEEKEND, WITH NIGHT TO MORNING MARINE LAYER CLOUDS EXPECTED TO
AFFECT THE COASTS TO THE VALLEYS. WILL LIKELY NEED FROST AND
FREEZE PRODUCTS FOR FRIDAY NIGHT AS WELL, AS OVERNIGHT LOW
TEMPERATURES SHOULD STILL BE QUITE COLD.
***FROM PREVIOUS DISCUSSION***
WINDS HAVE MORE OR LESS RETURNED TO NORMAL WITH ONSHORE BREEZES
NOW WELL INTO THE INTERIOR. HUMIDITIES HAVE BEEN SLOWER TO RECOVER
AND ARE STILL MOSTLY BELOW 30 PERCENT EXCEPT RIGHT AT THE
IMMEDIATE COAST. TEMPERATURES TODAY WERE 4-8 DEGREES COOLER
ACROSS COAST BUT NOT SO MUCH INLAND.
TONIGHT MODELS CONTINUE TO SHOW INCREASING ONSHORE FLOW AND THE
EVENTUAL RETURN OF MARINE LAYER STRATUS. CONFIDENCE IN THIS PART
OF THE FORECAST IS DEFINITELY ON THE LOWER SIDE GIVEN THE
HUNDREDS OF MILES OF MOSTLY CLEAR SKIES TO OUR WEST AND STILL VERY
LOW HUMIDITIES OVER THE MAINLAND. THE HREF INCREASED CHANCES OF
STRATUS DEVELOPMENT FROM 50 TO ALMOST 70 PERCENT TONIGHT AND
FORECAST SOUNDINGS INDICATE A RAPIDLY DEEPENING MARINE INVERSION
FROM BASICALLY THE SURFACE TO 3000 FEET SATURDAY MORNING. SO WILL
STICK WITH LOW CLOUDS AND FOG DEVELOPING AT LEAST BY EARLY
SATURDAY AND SPREADING INTO THE COASTAL VALLEYS. WOULD NOT BE ALL
THAT SURPRISED IF THIS DID NOT PAN OUT BUT CHANCES ARE HIGHER THAT
IT WILL.
THE UNCERTAINTY IN THE MARINE LAYER HAS A SIGNIFICANT IMPACT ON
THE OVERNIGHT NIGHT LOWS. IT'S BEEN QUITE COLD AT NIGHT LATELY IN
WIND PROTECTED AREAS AND BUT THE SWITCH TO ONSHORE FLOW AND THE
LIKELY FORMATION OF A LOW CLOUD DECK COULD LEAD TO MUCH WARMER
OVERNIGHT LOWS, DEPENDING ON WHEN THE CLOUDS DEVELOP. GIVEN THAT
CLOUDS SHOULD FORM FAIRLY LATE AT NIGHT, WENT AHEAD AND ISSUED
ANOTHER ROUND OF FREEZE/FROST HAZARDS, BUT THIS MAY NOT PAN OUT IN
SOME OR EVEN MOST AREAS. ON THE OTHER HAND, IF A DEEP STRATUS
DEVELOPS AS THE HIGH RES MODELS ARE INDICATING, THERE IS ALSO A
CHANCE OF SOME MORNING DRIZZLE, ESPECIALLY IN UPSLOPE AREAS.
A SIMILAR SCENARIO IS POSSIBLE SATURDAY MORNING, HOWEVER MODELS
CONTINUE TO INDICATE A 5.1MB OFFSHORE TREND SO IT'S UNCERTAIN HOW
THIS WILL IMPACT THE STRATUS FORMATION. OVERALL, TEMPERATURES
EXPECTED TO BE QUITE COOL OVER THE WEEKEND WITH HIGHS TOPPING OUT
AROUND 60 FOR COAST AND VALLEYS.
LONG TERM (MON-THU)
16/233 PM.
THE ECMWF ENSEMBLES CONTINUE TO FAVOR LATE MONDAY INTO TUESDAY FOR
THE RETURN OF OFFSHORE WINDS FOLLOWING THE PASSAGE OF A VERY LARGE
AND VERY COLD LOW PRESSURE SYSTEM THAT WILL BRING MUCH COLDER THAN
NORMAL TEMPERATURES TO MOST OF THE US NEXT WEEK. DETERMINISTIC
SOLUTIONS ARE STILL BOUNCING AROUND QUITE A BIT, WITH THE 00Z
ECMWF LAST NIGHT PREDICTING A -9.7 LAX/DAG GRADIENT NEXT THURSDAY,
ONLY TO SHIFT GEARS AND MOVE THAT TUESDAY INSTEAD. SO AT LEAST
THAT LINES UP WITH WHAT THE ENSEMBLES HAVE BEEN FAVORING FOR THE
LAST SEVERAL DAYS. WITH INCREASING CONFIDENCE ON THE TIMING,
THERE'S STILL QUITE A RANGE OF WIND POSSIBILITIES, BUT MOST
INDICATIONS ARE IT WILL AT LEAST BE A MODERATE EVENT, AROUND A 60%
CHANCE WITH WINDS MOSTLY IN THE 30-50 MPH RANGE, WITH ONLY A 20%
CHANCE OF EITHER A STRONG OR WEAK EVENT. AFTER TUESDAY IT
APPEARS LIKELY OFFSHORE FLOW WILL CONTINUE THROUGH AT LEAST
THURSDAY BUT NOT AS STRONG.
ONE POSSIBLE DIFFERENCE WITH THIS NEXT EVENT IS WITH THE
HUMIDITIES. THEY HAVE BEEN LOW THROUGHOUT THE LAST COUPLE WEEKS
BUT NEXT WEEK THE EC ENSEMBLES ARE STRONGLY IN FAVOR OF AN EVEN
DRIER PATTERN, WITH PW'S AROUND A TENTH OF AN INCH. THIS COULD
MEAN WIDESPREAD HUMIDITIES OF 10% OR LESS, WITH SOME AREAS EVEN
BELOW 5%.
WARMING TEMPERATURES EXPECTED FOR THE END OF THE WEEK AS HIGH
PRESSURE STARTS TO BUILD IN FROM THE WEST. MAY STILL BE DEALING
WITH AT LEAST MODERATE OFFSHORE WINDS THURSDAY/FRIDAY AS THE
ECMWF SHOWS A SECONDARY, BUT SLIGHTLY WEAKER PEAK IN OFFSHORE
FLOW.
AVIATION
17/0602Z.
AT 05Z AT KLAX, THERE WAS NO MARINE LAYER NOR AN INVERSION.
OVERALL, LOW TO MODERATE CONFIDENCE IN 06Z TAF PACKAGE. LOWEST
CONFIDENCE FOR LOW CLOUDS/FOG DEVELOPMENT, WITH BEST CHANCES FOR
LA COASTAL AREAS. THERE IS A 30% CHANCE FOR SUB-VFR CONDS FOR KPRB
FROM 12Z TO 18Z. THERE IS A 30% CHANCE FOR IFR CONDS AT KSMO FROM
12Z TO 18Z. TIMING OF FLIGHT CIG/VSBY RESTRICTIONS MAY BE OFF +/-
2 HOURS AND FLIGHT CAT COULD BE OFF ONE OR TWO.
KLAX...HIGH CONFIDENCE IN VFR CONDS THRU 08Z, THEN LOW CONFIDENCE
DUE TO AN INCREASING CHANCE OF STRATUS. THERE IS A 30% CHANCE THAT
CIGS NEVER FALL BELOW BKN/OVC010. GOOD CONFIDENCE THAT EAST WIND
COMPONENT WILL STAY UNDER 8 KT.
KBUR...HIGH CONFIDENCE IN VFR CONDS THRU 08Z, THEN LOW CONFIDENCE
DUE TO AN INCREASING CHANCE OF STRATUS. THERE IS A 30% CHANCE
OF CIGS FALLING BELOW BKN/OVC010 (IFR CONDS) FROM 10Z TO 18Z.
MARINE
16/833 PM.
IN THE OUTER WATERS, THERE IS A 30% CHANCE OF SMALL CRAFT
ADVISORY (SCA) LEVEL WINDS FROM PT. CONCEPTION TO SAN NICOLAS
ISLAND FRI AFTERNOON THRU FRI NIGHT, AND AGAIN SUN NIGHT/MON.
THERE IS ALSO A 30% CHANCE OF SCA WIND GUSTS OUT OF THE NE FOR MON
NIGHT AND TUE MORNING FOR THE SOUTHERN OUTER WATERS (PZZ676).
OTHERWISE, SUB-ADVISORY CONDITIONS ARE EXPECTED THROUGH TUE NIGHT.
FOR THE INNER WATERS NORTH OF PT SAL, SUB-ADVISORY CONDS ARE
EXPECTED THRU TUE NIGHT.
IN THE SANTA BARBARA CHANNEL, THERE IS A 20%-30% CHANCE OF SCA
LEVEL W WINDS OVER WESTERN PORTIONS FRI AFTERNOON AND EVENING.
THERE IS ALSO A 30%-40% CHANCE OF SCA EASTERLY WIND GUSTS OVER
EASTERN PORTIONS MON NIGHT AND TUESDAY. OTHERWISE, FAIRLY BENIGN
CONDITIONS ARE EXPECTED THRU TUE NIGHT.
IN THE SOUTHERN INNER WATERS, EXCEPT FOR A 30%-40% CHANCE OF
SCA LEVEL NE WINDS MON NIGHT AND TUE MAINLY NEARSHORE FROM MALIBU
TO SANTA MONICA, SCA CONDS ARE NOT EXPECTED THRU TUE NIGHT.
LOX WATCHES/WARNINGS/ADVISORIES
CA...FROST ADVISORY IN EFFECT UNTIL 9 AM PST FRIDAY FOR ZONES
340-341-358-372-374. (SEE LAXNPWLOX).
FREEZE WARNING IN EFFECT UNTIL 9 AM PST FRIDAY FOR ZONES
343-344-346>348-357-371-381>383. (SEE LAXNPWLOX).
PZ...NONE.
PUBLIC...PHILLIPS/MW
AVIATION...BLACK
MARINE...SIRARD/SMITH
SYNOPSIS...MW/SMITH
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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