Weather Service Report


231 
FXUS66 KLOX 281130
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
430 AM PDT MON JUL 28 2014

NEW AVIATION DISCUSSION

.SYNOPSIS...
MONSOONAL FLOW WILL BRING SCATTERED SHOWERS AND ISOLATED 
THUNDERSTORMS TO THE REGION THIS MORNING...WITH A SLIGHT CHANCE 
CONTINUING IN THE MOUNTAINS AND ANTELOPE VALLEY THROUGH THIS 
EVENING. A RATHER STRONG UPPER LEVEL HIGH JUST TO THE SOUTH OF THE 
FOUR CORNERS AREA WILL PERSIST THROUGH THE WEEKEND. TEMPERATURES 
WILL REMAIN ABOVE NORMAL ACROSS MOST OF THE REGION THROUGH THE 
PERIOD...WITH NIGHT THROUGH MORNING LOW CLOUDS AND FOG CONFINED 
MOSTLY TO THE COASTAL PLAIN.

&&

.SHORT TERM (TODAY-WED)...A DECENT VORT MAX ROTATING NORTHWESTWARD 
TOWARD THE REGION IN THE MOIST MONSOONAL FLOW ALOFT HAS CAUSED AN 
AREA OF SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP ACROSS 
SOUTHERN AND EASTERN LOS ANGELES COUNTY AND THE SOUTHERN COASTAL 
WATERS. SO FAR...RAINFALL TOTALS SINCE MIDNIGHT HAVE BEEN GENERALLY 
ONE TENTH OF AN INCH OR LESS...WITH ISOLATED HIGHER AMOUNTS. ANOTHER 
AREA OF SHOWERS HAS DEVELOPED ACROSS SLO AND WESTERN SANTA BARBARA 
COUNTIES...BUT NO LIGHTNING HAS YET BEEN DETECTED IN THIS REGION. 
SHOWER/TSTM ACTIVITY WILL PROBABLY DRIFT INTO AT LEAST EASTERN 
SECTIONS OF VTU COUNTY BY DAYBREAK. WILL JUST GO WITH AREAL 
SHWR/TSTM WORDING FOR ALL AREAS THIS MORNING...WITH THE BEST 
COVERAGE LIKELY REMAINING FOCUSED OVER L.A. AND ERN VTU COUNTIES.

AS THE VORT LIFTS NORTH OF THE REGION...THE MID LEVEL LIFT WILL 
WEAKEN...SO EXPECT SHOWER ACTIVITY TO DECREASE OR END IN MOST 
COASTAL AND VALLEY AREAS BY NOON OR SO. THEN...THERE SHOULD BE SOME 
PARTIAL CLEARING. THE WRF SHOWS SOME MARGINAL INSTABILITY IN THE 
MTNS AND THE ANTELOPE VALLEY THIS AFTERNOON AND EVENING...SO
THERE WILL BE A LINGERING SLIGHT CHANCE OF SHOWERS AND TSTMS THERE 
AS THE LIFTING MECHANISM FOR CONVECTION TRANSITIONS FROM 
SYNOPTICALLY INDUCED TO OROGRAPHICALLY INDUCED. A TSTM OR TWO COULD
DRIFT INTO THE CUYAMA VLY AND THE INTERIOR VLYS OF SERN SLO COUNTY 
AS WELL. WITH GOOD PRECIPITABLE WATER VALUES AND WEAK FLOW 
ALOFT...THERE IS A MODERATE THREAT OF FLASH FLOODING DUE TO 
SLOW STORM MOVEMENT. HOWEVER...CONFIDENCE IN FLASH FLOODING ISSUES 
IS NOT QUITE HIGH ENOUGH TO WARRANT FLASH FLOOD WATCHES AT THIS 
TIME...MAINLY BECAUSE THERE IS SOME QUESTION AS TO WHETHER OR NOT 
THERE WILL BE ENOUGH HEATING TO PRODUCE MORE THAN ISOLATED AFTERNOON 
TSTMS. THIS WILL HAVE TO BE MONITORED CLOSELY TODAY. MAX TEMPS WILL 
BE VERY TRICKY TODAY. THE AIR MASS IS QUITE WARM...AND TEMPS WILL 
RISE QUICKLY AS THEY DID LATE IN THE DAY ON SUNDAY IF SKIES BECOME 
PARTLY CLOUDY. 

AN UPPER HIGH JUST SOUTH OF THE FOUR CORNERS REGION WILL EXPAND INTO 
THE REGION ON TUE AND LINGER THROUGH WED...WHICH SHOULD DECREASE THE 
INFLUX OF MONSOONAL MOISTURE INTO THE FORECAST AREA. HAVE DECIDED TO 
KEEP POPS OUT OF THE FORECAST...ALTHOUGH IT IS POSSIBLE THAT THERE 
COULD BE ENOUGH LINGERING MOISTURE FOR A SLIGHT CHANCE OF 
SHOWERS/TSTMS TUE AFTERNOON AND EVENING...MAINLY IN THE MTNS OF L.A. 
AND VTU COUNTIES AND THE ANTELOPE VALLEY. WITH DECREASING MID LEVEL 
MOISTURE...EXPECT NIGHT/MORNING STRATUS TO BECOME BETTER 
ORGANIZED...BUT CONFINED TO LOCATIONS WITHIN A FEW MILES OF THE 
COAST TUE AND WED. MAX TEMPS WILL LIKELY EDGE UPWARD A BIT EACH 
DAY...REMAINING ABOVE NORMAL JUST ABOUT EVERYWHERE. 


.LONG TERM (THU-SUN)...VERY LITTLE CHANGE IN THE UPPER 
PATTERN...WITH A RATHER STRONG UPPER HIGH LINGERING OVER ARIZONA AND 
NEW MEXICO...WITH RIDGING EXTENDING WESTWARD INTO THE FORECAST AREA. 
EXPECT NIGHT THROUGH MORNING STRATUS TO REMAIN CONFINED TO LOCATIONS 
WITHIN A FEW MILES OF THE COAST. TEMPS WILL GENERALLY BE 4 TO 8  
DEGREES ABOVE NORMAL IN MOST AREAS THROUGH THE PERIOD. 

&&

.AVIATION...

27/1130Z

THERE IS A 20 TO 30 PERCENT CHANCE OF A THUNDERSTORM TODAY AT ANY 
LOCATION TODAY THROUGH EARLY AFTERNOON. THE CHANCE OF THUNDERSTORMS 
WILL PERSIST THROUGH THE AFTERNOON OVER THE MOUNTAINS. LOW 
CONFIDENCE IN ALL COASTAL TAFS AS CIGS MAY APPEAR OR DISAPPEAR AT 
RANDOM THROUGH 17Z. THE LOW CLOUDS COULD ARRIVE A FEW HOURS EARLIER 
THAN FCST TONIGHT.

KLAX...LOW CONFIDENCE IN TAF CIGS COULD DISSIPATE AT ANY TIME BUT IF 
THEY DOE THERE IS A 40 PERCENT CHANCE THAT THE IFR CIGS WILL REFORM. 
A 20 PERCENT CHC OF A SHOWER OR THUNDERSTORM THROUGH 20Z.

KBUR...GOOD CONFIDENCE IN TAF WITH A 20 PERCENT CHC OF A SHOWER OR 
THUNDERSTORM THROUGH 20Z.

&&

.MARINE...

28/300 AM

A SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE COASTAL WATERS THROUGH 
MIDDAY TODAY... WITH THE GREATEST PROBABILITY IN THE SOUTHERN 
WATERS. OTHER THAN NEAR SHOWERS AND THUNDERSTORMS...WEAK TO LOCALLY 
MODERATE WINDS ARE EXPECTED ACROSS THE COASTAL WATERS THROUGH MID 
WEEK.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

PUBLIC...DB
AVIATION/MARINE...ASR

WWW.WEATHER.GOV/LOSANGELES



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