Weather Service Report


347 
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

WWW.WEATHER.GOV/LOSANGELES



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