Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 282223
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
220 PM PST SAT FEB 28 2015

.SYNOPSIS...

A COLD LOW PRESSURE SYSTEM WILL BRING SHOWERS AND MOUNTAIN SNOW THIS
WEEKEND...ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS. ANOTHER LOW
PRESSURE SYSTEM WILL BRING SIMILAR CONDITIONS TO THE AREA MONDAY AND
MONDAY NIGHT. DRY WEATHER IS EXPECTED STARTING TUESDAY. A BUILDING
RIDGE OF HIGH PRESSURE WILL RESULT IN A WARMING TREND FOR THE
REMAINDER OF NEXT WEEK.

&&

.SHORT TERM (TODAY-TUE)...

UNSETTLED WEATHER EXPECTED THROUGH MONDAY NIGHT...AS A COUPLE OF
COLD UPPER-LEVEL LOW PRESSURE SYSTEMS MOVES THROUGH THE AREA. AS OF
100 PM...THE FIRST UPPER LOW WHICH IS ASSOCIATED WITH A POSITIVELY
TILTED TROUGH...WAS CENTERED OVER CENTRAL CA. THIS UPPER LOW WILL
MOVE SOUTHWARD AND BECOME CENTERED OVER PT CONCEPTION BY SUNDAY
MORNING. THE UPPER LOW WILL SLOWLY DRIFT SOUTHWARD THROUGH THE
CALIFORNIA BIGHT THROUGH SUNDAY NIGHT...THEN OPEN UP AND MOVE INLAND
ON MONDAY AS THE SECOND UPPER-LOW STARTS TO DIVES SOUTH.

SO FAR TODAY...MOST OF THE SHOWER ACTIVITY HAS REMAINED FROM THE
VENTURA AND SANTA BARBARA COUNTY MOUNTAINS AND POINTS N. SHOWER
ACTIVITY SHOULD INCREASE FOR THE COASTAL AND VALLEY AREAS S OF THE
MOUNTAINS LATER THIS AFTERNOON AND THIS EVENING...AS THE UPPER-LOW
CONTINUES TO MOVE S. WHILE IT IS DIFFICULT TO PIN DOWN EXACTLY WHEN
AND HOW MUCH IT WILL RAIN DUE TO THE CONVECTIVE NATURE OF THE PRECIP
EXPECTED...IT LOOKS LIKE THE BEST CHANCE FOR RAIN IN VENTURA AND LA
COUNTY WILL BE TONIGHT AND SUNDAY MORNING...WHEN THE BEST SYNOPTIC
SCALE LIFT WILL OCCUR AHEAD OF THE APPROACHING UPPER LOW. SHOWERS
WILL LIKELY CONTINUE THROUGH MONDAY MORNING...BUT WILL BECOME LESS
NUMEROUS SUNDAY NIGHT INTO MONDAY MORNING...AS THE FIRST UPPER LOW
MOVES EAST.

A SLIGHT CHANCE OF TSTORMS IS IN THE FORECAST FOR THE ENTIRE AREA
STARTING TONIGHT. SO FAR THERE HAVE ONLY BEEN A COUPLE LIGHTNING
STRIKES WELL TO THE N OF OUR CWA...WHERE THE NAM IS SHOWING SOME
WEAK INSTABILITY WITH OVER 500 J/KG OF CAPE. NOT OVERLY CONFIDENT IN
TSTORMS FOR OUR AREA TONIGHT WITH CAPE VALUES GENERALLY LESS THAN
200 J/KG...BUT WILL KEEP A SLIGHT CHANCE IN THE FORECAST WITH THE
UPPER LOW APPROACHING. TSTORMS COULD BE MORE OF A PROBLEM DURING THE
DAY TOMORROW AS THE UPPER LOW MOVES DIRECTLY OVERHEAD AND CAPE
VALUES EXCEED 500 J/KG OVER SOME OF THE MOUNTAINS WITH THE ADDED
DAYTIME HEATING. ANY TSTORMS THAT DEVELOP TOMORROW WILL ALSO BE
SLOWER MOVING THAN TODAY...WITH MUCH WEAKER STEARING WINDS...SO
FLASH FLOODING AND DEBRIS FLOWS NEAR RECENT BURN AREAS COULD BE MORE
OF A CONCERN TOMORROW.

AREA AVERAGE RAINFALL AMOUNTS THROUGH MONDAY MORNING WILL GENERALLY
BE 0.10-0.25" FOR THE COAST AND VALLEY AREAS...AND 0.50-1.00" IN THE
MOUNTAINS. HOWEVER...AMOUNTS WILL BE HIGHLY VARIABLE AS PREVIOUSLY
MENTIONED DUE TO THE SHOWERY NATURE.

NO CHANGES ARE PLANNED FOR THE SNOWFALL AMOUNTS OR TIMING WITH THE
WINTER WEATHER ADVISORY...WHICH IS IN EFFECT FROM 4PM THIS AFTERNOON
THROUGH 4AM MONDAY FOR THE VENTURA AND LA COUNTY MOUNTAINS...AND 4PM
THIS AFTERNOON THROUGH 10PM SUNDAY FOR THE SANTA BARBARA COUNTY
MOUNTAINS. PLEASE SEE LAXWSWLOX FOR MORE DETAILS.

AFTER A LULL IN THE SHOWER ACTIVITY ON MONDAY MORNING...THE THREAT
OF SHOWERS AND ISOLATED TSTORMS WILL INCREASE AGAIN MONDAY AFTERNOON
THROUGH MONDAY EVENING...AS THE SECOND UPPER-LOW QUICKLY DIVES DOWN
FROM THE N. SHOWERS SHOULD QUICKLY TAPER OFF BY TUESAY MORNING. RAIN
AND SNOW AMOUNTS WILL LIKELY BE LOWER WITH THE SECOND SYSTEM AS IT
WILL BE FASTER MOVING...BUT SNOW LEVELS WILL REMAIN AROUND 4000
FEET. SHOULD SEE MORE SUN THAN CLOUDS ON TUESDAY...BUT TEMPERATURES
WILL REMAIN SLIGHTLY BELOW NORMAL.

.LONG TERM (WED-SAT)...

MODELS ARE IN GOOD AGREEMENT THAT A BUILDING RIDGE OF HIGH PRESSURE
WILL BRING SOME VERY NICE WEATHER IN THE LONG TERM. SKIES SHOULD
REMAIN MOSTLY CLEAR/SUNNY INTO THE WEEKEND. TEMPERATURES WILL CLIMB
ABOVE NORMAL BY THURSDAY AND REACH THE MID 70S TO LOW 80S FOR THE
COASTAL AND VALLEY AREAS BY FRIDAY AND SATURDAY.

&&

.AVIATION...28/1800Z...

MID/UPPER LEVEL TROUGH CENTER OVER CENTRAL/NORTHERN CALIFORNIA WILL
SHIFT SOUTH. UPPER LEVEL STRONG WEST-SOUTHWEST WINDS WILL BECOME
STRONG SOUTHWEST WHILE MID LEVEL MODERATE WEST WINDS BECOME LIGHT TO
MODERATE SOUTHWEST AFTER 01/05Z OVER THE AREA. FREEZING LEVEL WAS
APPROXIMATELY 6KFT THIS MORNING AND WILL DIFFER BY MINUS 1KFT SUNDAY
MORNING. ISOLATED THUNDERSTORMS WITH TOPS APPROXIMATELY 30KFT ARE
EXPECTED TO MOVE EAST-NORTHEAST AFTER 01/05Z.

MARINE LAYER AT LAX AT 1715Z IS NONE.

KLAX...CHANCE CIGS 030 AT TIMES THROUGH 28/20Z THEN CHANCE CIGS 030
AND -SHRA BETWEEN 01/03-01/11Z. CHANCE CIGS 030-035 AND -TSRA
BETWEEN 01/11-01/15Z THEN CHANCE CIGS 035-040 THEREAFTER.

KBUR...CHANCE CIGS 025 THROUGH 28/19Z THEN CHANCE CIGS 035 BETWEEN
29/19-01/11Z. CHANCE -TSRA CIGS 030 BETWEEN 01/11-01/15Z.

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS


&&

.MARINE...28/200 PM...

SMALL CRAFT ADVISORY CONDITIONS ARE NOT EXPECTED THROUGH THE PERIOD.
OTHERWISE ISOLATED THUNDERSTORMS ARE EXPECTED THROUGH MONDAY
MORNING. THE THUNDERSTORMS WILL MOVE WEST-SOUTHWEST AROUND 28 KT
TODAY THROUGH THIS AFTERNOON THEN AS THE TROUGH AXIS SETTLES OVER
THE AREA TONIGHT THROUGH SUNDAY NIGHT THE STORMS SOUTH OF POINT
CONCEPTION WILL MOVE NORTHEAST 25 KT AND MOVE SOUTHWEST AROUND 15 KT
NORTH OF POINT CONCEPTION. A SWELL GENERATED IN THE SOUTHERN
HEMISPHERE WITHIN 190-210 DEGREES RELATIVE TO VENTURA COUNTY LAST
TUESDAY IS EXPECTED TO ARRIVE NEXT WEEK TUE THROUGH WEDNESDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY (SEE LAXWSWLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).

&&

$$

PUBLIC...SUKUP
AVIATION/MARINE...30
SYNOPSIS...SMITH

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