Severe Thunderstorm Warning 4, NWS Los Angeles, CA

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
210 PM PDT MON SEP 10 2012

.SYNOPSIS...
ISOLATED THUNDERSTORMS WILL LIKELY REDEVELOP OVER THE LOS ANGELES
AND VENTURA COUNTY MOUNTAINS AND ANTELOPE VALLEY THROUGH THIS
EVENING...WITH A SLIGHT CHANCE AGAIN ON TUESDAY. TEMPERATURES SHOULD
LOWER TO NORMAL ON TUESDAY...THEN WARM UP THROUGH THE END OF THE
WEEK AS A RIDGE FROM THE SOUTHEAST BUILDS IN.

&&

.SHORT TERM (TODAY-THURSDAY)...
MONSOONAL MOISTURE CONTINUES TO BE THE BIG STORY TODAY...AS
THUNDERSTORMS ARE TRYING TO DEVELOP OVER THE LA/VTU MTNS. PLENTY OF
ACTION TO OUR EAST MAY RESULT IN OUTFLOW INTERACTIONS LEADING TO
DEEP CONVECTION OVER LA COUNTY AGAIN...SO WILL BE KEEPING A SHARP
EYE ON THAT. WILL KEEP CURRENT FLASH FLOOD WATCHES GOING UNTOUCHED AS
A RESULT. WITH LIGHT FLOW ALOFT...MOISTURE WILL LINGER AROUND
THROUGH TOMORROW...THOUGH WILL BE ON THE DOWNTURN. ADDED A SLIGHT
CHANCE TO EASTERN LA COUNTY AS A RESULT...BUT FLOODING CONCERNS
SHOULD BE LESS WITH DECREASING MOISTURE AND INCREASING STEERING FLOW.

TEMPERATURES RUNNING LOWER ALMOST EVERYWHERE TODAY THANKS TO A WEAK
TROUGH DROPPING INTO NORTHERN CALIFORNIA AND INCREASED ONSHORE
GRADIENTS. THIS TREND WILL CONTINUE TOMORROW...WHEN TEMPERATURES
SHOULD RETURN BACK TO NORMAL. LOW CLOUDS AND FOG WILL MAKE A RETURN
ALONG THE CENTRAL COAST BY TUESDAY...WITH A 30 PERCENT CHANCE OF
TOUCHING THE LA/VTU BEACHES.

A RIDGE CENTERED JUST SOUTH OF TEXAS WILL SLOWLY BUILD TO THE
NORTHWEST ON WEDNESDAY...THEN QUICKLY KNIFE NORTHWARD INTO OREGON ON
THURSDAY. THIS WILL BRING A NOTICEABLE WARMUP ONCE AGAIN...TO ABOVE
NORMAL BY THURSDAY. THE LOW CLOUDS AND FOG SHOULD STAY OFF THE COAST
WITH THE RIDGE AND WEAK OFFSHORE GRADS...BUT CANNOT DISMISS SOME FOG
NEAR THE IMMEDIATE BEACHES...ESPECIALLY ALONG THE CENTRAL COAST.
WHILE WED AND THU LOOKS DRY...EAST FLOW ALOFT WITH THE POSITION OF
THE RIDGE ON THU MAY BRING SOME MID-LEVEL MOISTURE.

.LONG TERM (FRIDAY-MONDAY)...
THE AFOREMENTIONED RIDGE WILL STRENGTHEN FRIDAY AND SATURDAY TO A
HEALTHY 591DM CORE. ANOTHER WARM UP IS ON TAP AS A RESULT...WITH
TRIPLE DIGIT TEMPERATURES IN MOST VALLEY AND LOWER MOUNTAIN
LOCATIONS. THE GFS AND ECMWF SHOW THE RIDGE WEAKENING ON
SUNDAY...BUT SOLUTIONS DIVERGE AFTER THAT...WITH THE GFS SHOWING A
BIG TROUGH OVER THE WEST COAST WHILE THE ECMWF BRINGS ANOTHER RIDGE.
WENT WITH THE GFS BASED ON CLIMOTOLOGY AND THE MAJORITY OF THE GFS
ENSEMBLE MEMBERS SUPPORTING THE OPERATIONAL MODEL.

&&

.AVIATION...10/1800Z.
ASIDE FROM THE THUNDERSTORM THREAT OVER THE ANTELOPE VALLEY...MOST
TAF SITES ARE EXPECTED TO REMAIN VFR THROUGH LATE THIS EVENING. THE
CENTRAL COAST IS EXPECTED TO SEE SOME IFR CONDITIONS IN FOG LATER
TONIGHT. THERE IS ONLY A SLIGHT CHANCE OF IFR CONDITIONS IN COASTAL
SECTIONS SOUTH OF POINT CONCEPTION.

KLAX...GOOD CONFIDENCE IN VFR CONDITIONS THROUGH TUESDAY. THERE
IS A 20 PERCENT CHANCE OF IFR CONDITIONS OVERNIGHT.

KBUR...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH TUESDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH (SEE LAXFFALOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

PUBLIC...KITTELL
AVIATION...SWEET
SYNOPSIS...RK

WWW.WEATHER.GOV/LOSANGELES

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
600 AM PDT MON SEP 10 2012

CAZ034>041-044>046-051>054-059-087-088-547-548-111300-
SAN LUIS OBISPO COUNTY CENTRAL COAST-
SANTA BARBARA COUNTY CENTRAL COAST-SANTA YNEZ VALLEY-
SAN LUIS OBISPO COUNTY INTERIOR VALLEYS-CUYAMA VALLEY-
SANTA BARBARA COUNTY SOUTH COAST-VENTURA COUNTY COAST-
LOS ANGELES COUNTY COAST INCLUDING DOWNTOWN LOS ANGELES-
VENTURA COUNTY INTERIOR VALLEYS-VENTURA COUNTY COASTAL VALLEYS-
SANTA MONICA MOUNTAINS RECREATIONAL AREA-
SAN LUIS OBISPO COUNTY MOUNTAINS-
SANTA BARBARA COUNTY MOUNTAINS-VENTURA COUNTY MOUNTAINS-
LOS ANGELES COUNTY MOUNTAINS EXCLUDING THE SANTA MONICA RANGE-
ANTELOPE VALLEY-CATALINA ISLAND-SANTA CLARITA VALLEY-
LOS ANGELES COUNTY SAN FERNANDO VALLEY-
LOS ANGELES COUNTY SAN GABRIEL VALLEY-
600 AM PDT MON SEP 10 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA.

.DAY ONE... TODAY AND TONIGHT

THERE IS A CHANCE OF THUNDERSTORMS IN THE ANTELOPE VALLEY AND THE
MOUNTAINS OF VENTURA AND LOS ANGELES COUNTIES THIS AFTERNOON
AND EVENING. SOME THUNDERSTORMS THIS AFTERNOON AND EVENING MAY
PRODUCE GUSTY WINDS...VERY HEAVY RAINFALL...AND FLASH FLOODING.
A FLASH FLOOD WATCH IS IN EFFECT FOR THESE AREAS.

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE LOS ANGELES
COUNTY VALLEYS THIS AFTERNOON AND EVENING. ANY THUNDERSTORM COULD
PRODUCE BRIEFLY HEAVY RAIN AND GUSTY WINDS.

LIGHTNING FROM ANY THUNDERSTORM MAY SPARK FIRES IN AREAS THAT DO NOT
RECEIVE MUCH RAINFALL.

* FLOOD WATCH................SEE WGUS66 KLOX - FFALOX FOR DETAILS *

.DAYS TWO THROUGH SEVEN... TUESDAY THROUGH SUNDAY

HOT WEATHER IS EXPECTED ACROSS INTERIOR SECTIONS OF SOUTHWESTERN
CALIFORNIA THURSDAY THROUGH AT LEAST SATURDAY. HIGHS TEMPERATURES
COULD REACH OR EXCEED 100 DEGREES EACH DAY IN THE ANTELOPE
VALLEY...ACROSS LOWER ELEVATIONS IN THE MOUNTAINS...AND IN THE WARMER
VALLEY LOCATIONS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

DB