Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 070033
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
535 PM PDT WED MAY 6 2015

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...

A COLD LOW PRESSURE SYSTEM WILL ARRIVE ON THURSDAY BRINGING A CHANCE
OF SHOWERS AND AND A SLIGHT CHANCE OF THUNDERSTORMS THROUGH FRIDAY
EVENING. TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH SATURDAY.
NEAR NORMAL TEMPERATURES ARE LIKELY BY SUNDAY AND EARLY NEXT WEEK.

&&

.SHORT TERM (TODAY-SAT)...

SOMEWHAT UNUSUAL MID-SPRING STORM SYSTEM IS STILL ON TRACK FOR
THURSDAY AND FRIDAY. NO MAJOR CHANGES TO THE PREVIOUS FORECAST
THINKING...BUT SOME MINOR CHANGES WERE MADE WITH THE AFTERNOON
UPDATE. MAIN CHANGE WAS TO INCREASE POPS SLIGHTLY OVER THE MOUNTAINS
AND SOME INTERIOR AREAS. POPS WERE INCREASED FROM SLIGHT CHANCE TO
CHANCE OVER INTERIOR SLO/SBA COUNTY TOMORROW AND FRIDAY. POPS WERE
ALSO INCREASED FROM SLIGHT CHANCE TO CHANCE ON FRIDAY FOR THE VTA/LA
MOUNTAINS...AS MODELS WERE ACTUALLY SHOWING MORE QPF ON FRIDAY THAN
TOMORROW.

THE COLD UPPER-LEVEL LOW THAT IS CURRENTLY OVER THE PACIFIC
NORTHWEST WILL MOVE SOUTHWARD TONIGHT AND BECOME CENTERED OVER
MONTEREY COUNTY BY TOMORROW EVENING. SEEMS LIKE THE BEST INSTABILITY
AND BEST CHANCE FOR T-STORMS TOMORROW WILL BE FROM THE VTA COUNTY
MOUNTAINS NORTH...BUT CAN`T RULE OUT AN ISOLATED T-STORM OVER THE LA
MOUNTAINS TOMORROW AFTERNOON. THERE WILL BE A BETTER CHANCE FOR
SHOWERS AND T-STORMS OVER LA COUNTY TOMORROW EVENING AS CYCLONIC
CURVATURE AND INSTABILITY INCREASE.

ON FRIDAY...THE UPPER LOW WILL BE OVER THE GREAT BASIN...BUT THERE
WILL STILL BE PLENTY OF INSTABILITY WITH COLD AIR ESTABLISHED ALOFT.
AS PREVIOUSLY MENTIONED...FRIDAY COULD ACTUALLY BE A BETTER DAY FOR
T-STORM ACTIVITY OVER VTA/LA THE MOUNTAINS...AND WITH STEERING WINDS
HAVING MORE OF A NORTHERLY COMPONENT...ANY T-STORMS THAT DEVELOP
OVER THE MOUNTAINS COULD DRIFT DOWN INTO THE COASTAL AND VALLEY
AREAS. SHOWER AND T-STORM ACTIVITY WILL CONTINUE INTO FRIDAY
EVENING...THEN DIMINISH OVERNIGHT AS THE UPPER LOW CONTINUES TO
DRIFT EAST AND INSTABILITY DIMINISHES.

FLASH FLOODING IS NOT EXPECTED TO BE A MAJOR ISSUE WITH THIS SYSTEM
AS T-STORMS WILL BE FAIRLY QUICK MOVING...WITH STEERING LEVEL WINDS
OF 20-35 KT. NONETHELESS...THOSE WITH INTERESTS NEAR BURN AREAS
SHOULD KEEP A CLOSE EYE ON THE WEATHER THURSDAY THROUGH FRIDAY
EVENING...AS A QUICK HALF AN INCH IN AN HOUR IS NOT OUT OF THE
QUESTION. PRECIP AMOUNTS WITH THIS SYSTEM WILL BE HIGHLY VARIABLE
DUE TO THE CONVECTIVE NATURE AND SOME VALLEY AND COASTAL AREAS MAY
NOT GET ANY RAIN AT ALL.

SNOW LEVELS WILL DROP TO AROUND 5000-6000 FEET TOMORROW AFTERNOON
AND REMAIN AROUND THERE THROUGH FRIDAY EVENING. BRIEFLY LOWER SNOW
LEVELS WILL BE POSSIBLE IN HEAVIER CONVECTIVE SHOWERS. SNOW
ACCUMULATIONS WILL BE SPARSE...BUT A COUPLE OF INCHES WILL BE
POSSIBLE ABOVE 6000-7000 FEET. DO NOT ANTICIPATE ANY WINTER WEATHER
ADVISORIES AT THIS TIME...AS CONFIDENCE IS TOO LOW IN 4 OR MORE
INCHES OF SNOW AND NO WINTER IMPACTS ARE EXPECTED ON MAJOR MOUNTAIN
PASSES.

GUSTY SOUTHWEST-WEST WINDS WILL CONTINUE FOR THE A.V. THROUGH
TOMORROW EVENING...WHERE A WIND ADVISORY IS IN PLACE. LOCAL GUSTS TO
45 MPH WILL ALSO BE POSSIBLE IN THE LA COUNTY MOUNTAINS
TOMORROW...BUT NO WIND ADVISORIES PLANNED.

FAIR WEATHER WILL RETURN BY SATURDAY AS UPPER-LEVEL RIDGING STARTS
TO TAKE PLACE. SHOULD BE A MOSTLY SUNNY DAY WITH SOME WARMING...BUT
TEMPS WILL STILL BE SLIGHTLY BELOW NORMAL.

.LONG TERM (SUN-WED)...

TEMPERATURES WILL RETURN TO NEAR NORMAL SUNDAY AS AN UPPER-LEVEL
RIDGE MOVES OVERHEAD. LONG RANGE MODELS AGREE THAT THE UPPER RIDGE
WILL BE SHORT-LIVED AS ANOTHER TROUGH OF LOW PRESSURE DEVELOPS EARLY
NEXT WEEK AND PERSISTS THROUGH WEDNESDAY. DESPITE THE TROUGH...NEAR
NORMAL TEMPERATURES ARE EXPECTED MONDAY THROUGH
WEDNESDAY...HOWEVER...THERE IS A GOOD CHANCE THAT MAY GRAY
CONDITIONS WILL RETURN DURING THIS TIME.

&&

.AVIATION...07/0025Z...

MARINE LAYER AT LAX AT 2355Z WAS 4500 FEET DEEP AND THE INVERSION
TOP WAS AT 5900 FEET WITH A TEMP OF 10 DEGREES C.

GENERALLY HI CONFIDENCE IN THE 00Z TAFS. LOW CLOUDS WITH MVFR CIGS
ARE LIKELY AT THE COASTAL AND VLY AIRFIELDS STARTING AS EARLY AS TAF
ISSUANCE TIME AT KSBP TO AS LATE AS 10Z AT KSBA AND KLAX. ONCE THE
MVFR CIGS DEVELOP...THE LOW CIGS SHOULD PERSIST THRU THU AFTERNOON.
HOWEVER...THE TIMING OF THE ONSET OF MVFR CIGS MAY BE OFF PLUS/MINUS
ONE TO TWO HOURS AT A FEW OF THE AIRFIELDS. FOR KWJF AND KPMD...
GUSTY W TO SW WINDS THIS EVENING WILL DIMINISH SOME TONIGHT THEN
BECOME STRONG AND GUSTY AGAIN BY THU AFTERNOON. THERE IS ALSO A
SLIGHT CHANCE OF THUNDERSTORMS FOR THU AFTERNOON AT THE SLO/SBA
COUNTY AIRFIELDS AS WELL AS FOR KWJF AND KPMD.

KLAX...GENERALLY HI CONFIDENCE IN THE 00Z TAF. LOW CLOUDS WITH MVFR
CIGS ARE LIKELY TO DEVELOP AROUND 10Z. ONCE THE MVFR CIGS DEVELOP...
THE LOW CIGS SHOULD PERSIST THRU ABOUT 04Z THU EVENING. HOWEVER...
THE TIMING OF THE ONSET OF MVFR CIGS MAY BE OFF PLUS/MINUS ONE TO
TWO HOURS.

KBUR...GENERALLY HI CONFIDENCE IN THE 00Z TAF. LOW CLOUDS WITH MVFR
CIGS ARE LIKELY TO DEVELOP AROUND 08Z. ONCE THE MVFR CIGS DEVELOP...
THE LOW CIGS SHOULD PERSIST THRU THU AFTERNOON. HOWEVER...THE TIMING
OF THE ONSET OF MVFR CIGS MAY BE OFF PLUS/MINUS ONE TO TWO HOURS.

&&

.MARINE...06/200 PM.

FOR THE OUTER WATERS...HIGH CONFIDENCE IN NORTHWEST WINDS REMAINING
AT SMALL CRAFT ADVISORY LEVELS THROUGH THURSDAY EVENING. THE WINDS
WILL DIMINISH TO BELOW ADVISORY LEVELS ON FRIDAY AND SATURDAY BUT
WILL STRENGTHEN AGAIN ON SUNDAY WITH A CHANCE OF REACHING SMALL
CRAFT ADVISORY LEVELS.

FOR THE INNER WATERS...
NORTH OF POINT CONCEPTION THERE IS MODERATE CONFIDENCE IN NORTHWEST
WINDS REACHING SMALL CRAFT ADVISORY LEVELS BY LATE THIS AFTERNOON
AND CONTINUING THROUGH THE EVENING THEN THE WIND WILL DIMINISH
THROUGH THE WEEKEND.

SOUTH OF POINT CONCEPTION THERE IS HIGH CONFIDENCE IN WEST TO
NORTHWEST WINDS REMAINING BELOW SMALL CRAFT ADVISORY LEVELS THROUGH
THE WEEKEND ALTHOUGH THERE IS A 30% CHANCE OF PERIODIC SMALL CRAFT
LEVEL GUSTS ACROSS THE WESTERN HALF OF THE SANTA BARBARA CHANNEL.

OVERALL... THERE IS A SLIGHT CHANCE OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE COASTAL WATERS ON THURSDAY AND
FRIDAY MOVING DOWN FROM THE NORTH. ANY THUNDERSTORMS WOULD BE
CAPABLE OF PRODUCING BRIEF HEAVY RAIN... GUSTY AND ERRATIC WINDS...
ROUGH SEAS... AND A POSSIBLE WATERSPOUT.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

$$

PUBLIC...SUKUP
AVIATION...SIRARD
MARINE...KJ
SYNOPSIS...SETO

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