Re: Stormy Weather

AREA FORECAST DISCUSSION
FXUS66 KLOX 261318
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
359 AM PST SAT JAN 26 2008


...A DANGEROUS STORM SYSTEM WILL AFFECT SOUTHWESTERN CALIFORNIA TONIGHT THROUGH SUNDAY EVENING...

.SHORT TERM...A POWERFUL UPPER LOW WAS CENTERED NEAR 35N/132W EARLY
THIS MORNING. DURING THE PAST 12 HOURS THE LOW HAS SHIFTED
WESTWARD...PULLING ITS POTENT FRONTAL SYSTEM WELL OFF THE COAST.
IT WILL CONTINUE TO DROP A BIT SWD TODAY...WITH THE FRONTAL
BAND REMAINING OFF THE COAST. THEREFORE...EXPECT THE WEATHER
TO BE RELATIVELY BENIGN ACROSS THE AREA TODAY...WITH PARTLY CLOUDY
SKIES...ALTHOUGH CLOUDS WILL PROBABLY INCREASE LATE IN THE DAY.
IT IS POSSIBLE THAT A FEW SHOWERS COULD AFFECT THE REGION...MAINLY
N OF PT CONCEPTION...SO HAVE LEFT A CHANCE/SLIGHT CHANCE OF SHOWERS
TODAY THERE...BUT MOST...IF NOT ALL OF THE DAYLIGHT HOURS SHOULD BE
FREE OF RAIN. WITH STRONG SFC GRADS AND DECENT S TO SE WINDS AT 850
MB...WIND ADVISORIES ARE IN EFFECT FOR CSTL AND VLY AREAS OF SLO AND
SBA COUNTIES TODAY. IN THE MTNS OF SBA AND SLO COUNTIES...WINDS ARE
EXPECTED TO INCREASE TO WARNING LEVELS...SO HIGH WIND WARNINGS ARE
IN EFFECT THERE. AS WINDS ALOFT INCREASE OVER L.A. AND VTU
COUNTIES...GUSTY SE WINDS SHOULD DEVELOP...WITH WINDS PROBABLY
REACHING ADVISORY LEVELS IN THE MTNS (INCLUDING THE SANTA MONICAS)
THIS AFTERNOON...AS WELL AS IN THE SANTA CLARITA VLY.

WEATHER CONDITIONS WILL DETERIORATE QUICKLY TONIGHT. INCREASINGLY
STRONG SLY FLOW THROUGHOUT THE ATMOSPHERE WILL PULL SUBTROPICAL
MOISTURE NWD INTO SRN CA TONIGHT AND PRECIPITABLE WATER VALUES
WILL RISE TO ABOUT 1.2 INCHES BY LATE TONIGHT. A POTENT VORT
ROTATING AROUND THE SRN SIDE OF THE UPPER LOW WILL APCH THE COAST
TONIGHT...AS A STRONG SUBTROPICAL JET BECOMES ALIGNED JUST TO THE S
OF THE AREA. MID AND UPPER LEVEL DYNAMICS WILL IMPROVE GREATLY
TONIGHT...AND VERY DEEP MOISTURE AND LIFT WILL CAUSE RAIN TO DEVELOP
FROM S TO N ACROSS THE AREA THIS EVENING...INCREASING IN INTENSITY
TONIGHT.

THE LATEST RUNS OF THE GFS AND THE WRF ARE ABOUT 3 HOURS SLOWER WITH
THE ONSET OF RAIN...BUT RAIN SHOULD STILL OVERSPREAD MUCH OF THE
AREA BY MIDNIGHT. WITH THE INCREASINGLY DIFFLUENT UPPER PATTERN...
XPCT SOME EMBEDDED THUNDERSTORMS TO DEVELOP ACROSS THE REGION
TONIGHT. INCREASINGLY STRONG SE TO SLY LOW LEVEL FLOW SHOULD PROVIDE
SIGNIFICANT OROGRAPHIC ENHANCEMENT...ESPECIALLY ON THE SOUTH FACING
SLOPES. IN FACT...THE LATEST RUN OF THE GFS SHOWS VERY IMPRESSIVE
SOUTHERLY 850 MB WINDS OF 60 TO 65 KNOTS FROM SBA TO L.A. COUNTIES
TONIGHT. WIND ADVISORIES ARE IN EFFECT FOR ALL COASTAL AND VLY AREAS
TONIGHT INTO SUNDAY MORNING. HIGH WIND WARNINGS WILL CONTINUE
FOR THE MTNS OF SLO AND SBA COUNTIES...AND WILL GO INTO EFFECT
ACROSS THE SANTA MONICA MTNS AND THE SANTA CLARITA VLY. PLEASE REFER
TO THE LATEST HIGH WIND WARNING/WIND ADVISORY PRODUCT FOR MORE
DETAILS ON THE WIND POTENTIAL. WINTER STORM WARNINGS HAVE BEEN
ISSUED FOR THE MTNS OF L.A. AND VTU COUNTIES...SO ALTHOUGH WINDS
WILL EXCEED HIGH WIND WARNING LEVELS THERE AS WELL...THEY ARE
COVERED BY THE WINTER STORM WARNING THERE.

AFTER THE MAIN FRONT MOVES THRU THE AREA EARLY SUNDAY MORNING... THE
STRONG COLD CORE OF THE UPPER SYSTEM WILL MOVE INTO THE REGION.
INCREASINGLY STRONG INSTABILITY AND DEEP MOISTURE WILL KEEP
HEAVY SHOWERS ACROSS THE REGION ON SUNDAY...WITH A GOOD CHANCE OF
THUNDERSTORMS...SOME WITH HAIL. CONVECTIVE PARAMETERS LOOK
FAVORABLE FOR STRONG THUNDERSTORMS ACROSS SOUTHERN CALIFORNIA ON
SUNDAY...WITH THE FCST AREA IN A FAVORABLE LOCATION WITH RESPECT TO
A VERY STRONG SUBTROPICAL JET...LIFTED INDEX VALUES DROPPING TO
BETWEEN 0 AND -3...500 MB TEMPERATURES AROUND -26 DEGREES
CELSIUS...AND CAPE VALUES AS HIGH AS 500 J/KG. ALSO...LOW LEVEL
SOUTHEAST FLOW TRANSITIONING TO STRONG SOUTHWEST FLOW ALOFT WILL
CREATE FAVORABLE SHEAR PROFILE FOR POSSIBLE ROTATING STORMS. AS A
RESULT...CONDITIONS LOOK FAVORABLE FOR LOW TOP SUPERCELL WHICH MAY
PRODUCE WATERSPOUTS AND ISOLATED SMALL TORNADOS ON SUNDAY. PLEASE
REFER TO THE LATEST SPECIAL WEATHER STATEMENT REGARDING THE
POTENTIAL SEVERE WEATHER RISK.

RAINFALL AMOUNTS ARE EXPECTED TO RANGE FROM 2 TO 4 INCHES ACROSS
COASTAL AND VALLEY AREAS SOUTH OF POINT CONCEPTION...WITH 4 TO 8
INCHES POSSIBLE IN THE FOOTHILLS AND MOUNTAINS. SOUTH FACING SLOPES
WILL LIKELY RECEIVE THE HIGHEST RAINFALL TOTALS. DURING THE HEIGHT
OF THE STORM...RAINFALL INTENSITIES BETWEEN ONE HALF INCH AND ONE
INCH PER HOUR ARE LIKELY...WITH LOCALLY HIGHER RATES POSSIBLE NEAR
THUNDERSTORMS AND ALONG SOUTH FACING SLOPES. THIS ANTICIPATED HIGH
INTENSITY RAINFALL WILL BRING A HIGH RISK OF SIGNIFICANT AND
DANGEROUS DEBRIS FLOW CONDITIONS TO THE BURN AREAS. IN
ADDITION...NON BURN AREAS WILL ALSO BE AT RISK FOR FLASH FLOODING IN
THE FORM OF SIGNIFICANT AND DANGEROUS ROADWAY FLOODING...CREEKS
OVERFLOWING THEIR BANKS...AND SUBSTANTIAL MUD AND ROCK SLIDE
ACTIVITY. FLOODING POTENTIAL IS GREATLY INCREASED FOR ALL OF SANTA
BARBARA...VENTURA...AND LOS ANGELES COUNTIES DUE TO SATURATED GROUND
CONDITIONS AND SUBSTANTIAL SNOWMELT. WILL HAVE TO CLOSELY MONITOR
MAIN STEM RIVER FLOODING POTENTIAL AS WELL...SINCE NEXT ROUND OF
HEAVY RAINFALL COULD BRING SOME POINTS TO NEAR FLOOD
STAGE...ESPECIALLY THE VENTURA RIVER. PLEASE REFER TO THE LATEST
FLASH FLOOD WATCH PRODUCT FOR MORE DETAILS.

DEEP SOUTHERLY FLOW AND SUBTROPICAL FEED WILL CAUSE SNOW LEVELS TO
RISE TO BETWEEN 6500 AND 7000 FEET TONIGHT...AND POSSIBLY
EVEN A BIT HIGHER. BEHIND THE MAIN FRONT...AS THE COLD CORE
APPROACHES...SNOW LEVELS ARE THEN EXPECTED TO LOWER TO AROUND 5000
FEET SUNDAY AFTERNOON...AND LOCALLY DOWN TO 4000 FEET IN HEAVIER
SHOWERS OR THUNDERSTORMS. AN ADDITIONAL 1 TO 2 FEET OF SNOW CAN BE
EXPECTED AT THE SKI RESORTS...WITH SOME HIGHER PEAKS EXPECTED TO
RECEIVE OVER 3 FEET OF ADDITIONAL SNOW. SNOW COULD LOCALLY FALL
ALONG INTERSTATE 5 NEAR THE GRAPEVINE BY SUNDAY AFTERNOON. IN
ADDITION TO THE HEAVY SNOW POTENTIAL...THERE WILL BE VERY STRONG
WIND GUSTS OVER 70 MPH TONIGHT THAT WILL BRING THE POTENTIAL FOR
BLIZZARD CONDITIONS TO THE HIGHER ELEVATIONS. PLEASE REFER TO THE
LATEST WINTER STORM WATCH PRODUCT FOR MORE DETAILS ON WINTER WEATHER
CONDITIONS.

CONDITIONS WILL BE DANGEROUS ACROSS THE COASTAL WATERS THROUGH THE
WEEKEND DUE TO THE COMBINATION OF STRONG WINDS...POTENTIAL FOR
THUNDERSTORMS AND WATERSPOUTS...AND HIGH WIND WAVES. LARGE
WIND WAVES COULD CAUSE SOME OVERFLOW ON SOUTH FACING BEACHES
SUCH AS MALIBU LATE TONIGHT AND SUNDAY MORNING. PLEASE REFER TO THE
LATEST MARINE WEATHER STATEMENT FOR MORE DETAILS.

SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE ACROSS THE AREA
SUNDAY NIGHT...BUT WILL GRADUALLY DECREASE IN COVERAGE AND
INTENSITY. WITH PLENTY OF MSTR LINGERING ACROSS THE REGION...MONDAY
WILL BE MOSTLY CLOUDY AND COOL...AND A CHANCE OF SHOWERS WILL
CONTINUE ACROSS THE AREA.

.LONG TERM...BROAD CYCLONIC NWLY FLOW PATTERN WILL CONTINUE ACROSS
THE AREA TUE AND WED. A SHORT WAVE MOVING THRU THIS FLOW WILL
THREATEN THE AREA WITH SOME SHOWERS TUE NIGHT/WED...BUT WITH THE
NWLY FLOW...AMTS SHOULD BE LIGHT...WITH THE BEST THREAT OF PRECIP ON
THE CENTRAL CST AND IN THE MTNS. WEAK RIDGING SHOULD BUILD ACROSS
THE AREA WED NIGHT THRU THU NIGHT...THEN ANOTHER SHORTWAVE WILL
BRING A SLIGHT CHANCE OF SHOWERS ON FRI. IT WILL BE QUITE COOL
ACROSS THE AREA THRU THE WEEK...WITH MAX TEMPERATURES GENERALLY 5 TO
10 DEGREES BELOW SEASONAL NORMS.


&&

.AVIATION...26/1300Z...VFR CONDS WILL PREVAIL THROUGH MUCH OF THE
DAY...EXCEPT FOR PATCHY RADIATIONAL FOG ACROSS PORTIONS OF ALL
VALLEY/COASTAL AREAS. VERY SPOTTY IN NATURE. SPOTTER FROM KVNY
REPORTED LIFR VSBYS DUE TO GROUND FOG. VFR CIGS WILL GIVE WAY TO
MVFR CIGS AND RAIN THIS EVENING IN LA/VTU COUNTIES...THEN MOVE
NORTH OF POINT CONCEPTION THIS EVENING. CONDITIONS WILL BEGIN TO
DETERIORATE THIS EVENING AS HEAVY RAIN AND STRONG SOUTHEAST TO EAST
WINDS DEVELOP ACROSS THE FORECAST AREA. THESE SE TO E WINDS WILL
CONTINUE THIS DIRECTION THROUGH SUNDAY MORNING. HEAVY RAIN WILL
CONTINUE THROUGH SUNDAY. THE ATMOSPHERE WILL BE PRIMED FOR
POTENTIAL SEVERE WX...ESPECIALLY ACROSS THE COASTAL REGION OF
LA/VTU/SBA COUNTIES ON SUNDAY AS WATERSPOUTS WILL BE A DEFINITE
POSSIBILITY AND POSSIBLY WEAK TORNADOES AS WATERSPOUTS COULD MOVE
ASHORE.


FOR KLAX...VFR CONDITIONS ARE EXPECTED THRU 22Z THEN MVFR CONDITIONS
WILL DEVELOP AS SHOWERS DEVELOP LATE AFTERNOON OR EARLY EVENING.
SHOWERS WILL TURN TO RAIN...HEAVY AT TIMES WITH IFR CIGS OVERNIGHT.
E TO SE WINDS 10 TO 12 KT ARE EXPECTED THIS MORNING. WINDS WILL
CONTINUE OUT OF THE E TO SE THROUGH SUNDAY MORNING...BEFORE TURNING
SW. PEAK SUSTAINED SOUTHEAST WINDS AT KLAX WILL OCCUR BETWEEN
09Z-18Z AT 25 KT WITH GUSTS TO 35 KT. WINDS WILL CONTINUE TO BE
GUSTY AND SHIFT TO SW ON SUNDAY AND CONTINUE GUSTY TO 20 TO 25 MPH
THROUGH THE AFTERNOON. WATERSPOUTS COULD DEVELOP OFF THE COAST NEAR
KLAX SUNDAY AS AIR MASS BECOMES QUITE UNSTABLE.

FOR KBUR...VFR CONDITIONS ARE EXPECTED THRU 22Z THEN MVFR CONDITIONS
WILL DEVELOP. SE WINDS TO 10 KT WILL PREVAIL AFT 20Z SAT. RAIN WILL
DEVELOP THIS EVENING.





.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING (SEE LAXWSWLOX).
HIGH WIND WARNING (SEE LAXNPWLOX).
FLASH FLOOD WATCH (SEE LAXFFALOX).
COASTAL FLOOD STATEMENT (SEE LAXCFWLOX).
WIND ADVISORY (SEE LAXNPWLOX).
STORM WARNING (SEE LAXCWFLOX).
GALE WARNING (SEE LAXCWFLOX).
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&




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AVIATION...KAPLAN

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