AREA FORECAST DISCUSSION
FXUS66 KLOX 162227
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
230 PM PST SAT JAN 16 2010

.SYNOPSIS...A WEAK LOW PRESSURE SYSTEM BROUGHT SOME CLOUDS AND
COOLER TEMPERATURES TO THE AREA TODAY. BEGINNING ON SUNDAY AND
CONTINUING THROUGH NEXT WEEK...A SERIES OF POWERFUL PACIFIC STORMS
WILL BRING SIGNIFICANT RAIN...SNOW AND PERIODS OF THUNDERSTORMS TO
THE AREA...ALONG WITH SOME VERY GUSTY WINDS.

&&

.SHORT TERM (TODAY-TUE)...
SEVERAL POWERFUL STORM SYSTEMS ARE LINING UP ACROSS THE PACIFIC THIS
AFTERNOON...BEING PUSHED BY A 200+ KT JET DIRECTLY TOWARDS
CALIFORNIA. TWO OF THESE SYSTEMS ARE EXPECTED TO IMPACT SOUTHERN
CALIFORNIA IN THE SHORT TERM. TODAYS FAIR WEATHER WILL PROBABLY THE
LAST DRY WEATHER FOR SOME TIME. TONIGHT AND EARLY ON SUNDAY...THE
CHANCE FOR SHOWERS BEGINS TO DEVELOP NORTH OF POINT CONCEPTION. THE
CHANCE OF PRECIPITATION WILL CONTINUE TO INCREASE ON SUNDAY AND MOVE
SOUTH AND EAST TO DURING THE DAY. WITH A SLIGHT CHANCE FOR LIGHT
RAIN TO REACH LA DURING THE AFTERNOON.

SUNDAY NIGHT AND MONDAY...THINGS BEGIN TO RAMP UP QUICKLY AND
SUBSTANTIALLY AS THE LEADING EDGE OF THE FIRST POWERFUL STORM BEGINS
TO MOVE ONSHORE NORTH OF POINT CONCEPTION EARLY MONDAY...MOVING
SOUTH OF POINT CONCEPTION AND INTO VENTURA AND LA COUNTIES DURING
THE AFTERNOON. THUNDERSTORMS WITH INTENSE DOWNPOURS WILL BE POSSIBLE
WITH THIS STORM MONDAY AFTERNOON AND EVENING. THIS WILL POSE A
SIGNIFICANT THREAT FOR DEBRIS FLOWS NEAR RECENT BURN AREAS...
INCLUDING THE STATION FIRE. IT IS IMPORTANT TO NOTE THAT RECENT
MODEL RUNS HAVE PROGRESSIVELY INCREASED THE STRENGTH OF MONDAYS
STORM DURING THE LAST TWO MODEL RUNS. AT THIS TIME...WE ARE
EXPECTING 1 TO 3 INCHES ALONG THE COAST WITH 3 TO 6 INCHES IN THE
FOOTHILLS AND MOUNTAINS. SNOW LEVELS WILL BE RUNNING IN THE 5000 TO
6000 FT RANGE. VERY HEAVY SNOW...POSSIBLY 1 TO 3 FEET...WILL BE
POSSIBLE AT ELEVATIONS ABOVE 6000 FEET. LOWER ACCUMULATIONS WILL BE
POSSIBLE DOWN TO AROUND 5000 FEET.

SOUTHERLY WINDS WILL ALSO BE ON THE INCREASE ON MONDAY ACROSS THE
MOUNTAINS AND SOME COASTAL AREAS. WIND GUSTS IN THE MOUNTAINS COULD
TOP 60 MPH ALONG WITH THE HEAVY SNOW. REFER TO THE WINTER STORM
WARNING FOR MORE DETAILS.

EARLY TUESDAY WE ARE LOOKING FOR A LITTLE BREAK BETWEEN STORM
SYSTEMS...BUT ANOTHER STORM SYSTEM IS EXPECT TO PASS THROUGH THE
REGION TUESDAY AFTERNOON AND EVENING. AT THIS TIME...THIS STORM
SYSTEM APPEARS TO BE NOT A STRONG AS THE MONDAY EVENT.

WITH MORE STORMS EXPECTED TO CONTINUE THROUGH MUCH OF THE WEEK...
THERE WILL BE OTHER THREATS THAT WE EXPECT TO DEVELOP. DUE TO THE
INSTABILITY EXPECTED WITH THESE STORMS...COASTAL AREAS MAY EXPECT TO
SEE THE THREAT FOR WATERSPOUTS. IN THE SHORT RANGE...THERE IS A
THREAT FOR WATERSPOUTS WITH THE STRONG SYSTEM ON MONDAY. BUT THE
THREAT SHOULD BE MORE SUBSTANTIAL WITH THE POWERFUL SYSTEM THAT IS
EXPECTED TO HIT THE REGION ON THURSDAY. IN ADDITION...SOME OF THE
HIGHEST SURF CONDITIONS WE HAVE SEEN IN YEARS IS EXPECTED TO DEVELOP
AROUND MID WEEK. EXPECT FURTHER DETAILS ON THESE THREATS TO BE
INCLUDED IN FUTURE FORECAST UPDATES.

.LONG TERM (TUE-FRI)...MEDIUM RANGE MODEL AGREEMENT IS PRETTY GOOD
THROUGH MID WEEK BEFORE THEY GET OUT OF PHASE. BOTH THE EC AND THE
GFS CALL FOR AT LEAST TWO MORE STRONG STORMS TO RAKE THE SOUTHLAND
IN THE EXTENDED PERIOD. THE GFS SEEMS TO PAINT THE MORE DOUR PICTURE
WITH BACK TO BACK POWERFUL STORMS ON BOTH WEDNESDAY AND THURSDAY...
WITH THE THURSDAY EVENT BEING PERHAPS THE MOST POWERFUL OF THE
WEEK...IN A WEEK OF STORMS. THE EC HAS THE SAME TWO STORMS...BUT
PERHAPS NOT QUITE AS POWERFUL...BUT STILL STRONG. ON FRIDAY...THE
GFS CALLS FOR A WET NORTHWESTERLY FLOW WITH SHOWERS CONTINUING
THROUGH FRIDAY WITH PERHAPS A BREAK ON SATURDAY. THE EC...HOWEVER...
KEEPS THE REGION UNDER MOIST SOUTHWEST TO WEST FLOW...WHICH LOOKS
WETTER THAN THE GFS. REGARDLESS...THE SIGNIFICANT TAKE AWAY FROM THE
EXTENDED IS THAT THE STORMS ARE EXPECTED TO CONTINUE THROUGH THE
WEEK AND INTO THE WEEKEND. THIS WILL LIKELY BE THE WETTEST WEEK WE
HAVE SEEN SINCE EARLY 2005 AND FAIRLY SIMILAR TO THE FIRST WEEK IN
FEB 1998. THIS WILL BRING THE POTENTIAL FOR WIDESPREAD ROCKSLIDES
AND DEBRIS FLOWS...EVEN OUTSIDE OF RECENT BURN AREAS. AND...BY WEEKS
END...WE WILL NEED TO KEEP AN EYE ON THE RIVERS.

&&

.AVIATION...16/1800Z.

A MID/UPPER LEVEL TROUGH OF LOW PRESSURE OVER THE AREA WILL CONTINUE
MOVING EAST. MODERATE MID LEVEL SOUTHWEST WINDS WILL BECOME LIGHT
WEST AND RELATIVELY MOIST AFTER 17/12Z WHILE MODERATE TO STRONG
UPPER LEVEL NORTHWEST WINDS MODERATE WEST AND MOIST AFTER 17/18Z
OVER THE AREA. FREEZING LEVEL WAS AROUND 10.5KFT AND WILL CONTINUE
TO DESCEND TO AROUND 8.5KFT THEN ASCEND TO 11KFT AFTER 17/12Z. WEAK
ONSHORE PRESSURE GRADIENT WILL BECOME WEAK TO MODERATE AFTER
17/18Z.

KLAX...IT IS LIKELY CIGS AROUND 150 WILL REDEVELOP AFTER 17/04Z AND
THERE IS A CHANCE DESCEND TO 060 AFTER 17/14Z AND 040 AFTER
17/20Z.

KBUR...IT IS LIKELY CIGS AROUND 150 WILL REDEVELOP AFTER 17/04Z AND
THERE IS A CHANCE DESCEND TO 060 AFTER 17/14Z.

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

&&

.MARINE...A SERIES OF STORMS WILL DEVELOP OVER THE CENTRAL AND
EASTERN PACIFIC THROUGH NEXT WEEK. IT IS VERY LIKELY GALES FORCE
WIND CONDITIONS WILL DEVELOP NEAR SHORE AS APPROACHING STORMS
STRENGTHEN AS THEY MOVE EAST OVER THE EASTERN PACIFIC. THERE IS A
CHANCE GALES WILL DEVELOP MONDAY AFTERNOON FROM POINT CONCEPTION TO
POINT PIEDRAS BLANCAS AND WEDNESDAY OVER THE ENTIRE AREA. STORMS
WILL LIKELY MOVE EAST OVER THE CENTRAL AND EASTERN PACIFIC ALONG
LATITUDE 35N WITHIN STORM FORCE WIND CONDITIONS. THE PERSISTENT
FETCH WILL LIKELY GENERATE SEAS TO 40 FEET WEST OF THE AREA. WHILE
IN ROUTE TO THE AREA THE SEAS WILL DECAY TO AROUND 25 TO 30 FEET AND
LIKELY ARRIVE WEDNESDAY NIGHT.

&&