FXUS64 KLIX 081329
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
729 AM CST TUE DEC 8 2009
.UPDATE...
.SOUNDING DISCUSSION...
HEAVY RAIN OCCURRED AT LAUNCH THIS MORNING...THERE WERE SEVERAL
AREAS OF EXTREME LAPSE RATES IN THE SOUNDING...UP TO 6 MINUTES OF
DATA WAS DELETED DUE TO CONTAMINATION. THE ATMOSPHERE IS VERY
SATURATED UP TO 650 MB WITH A SMALL AMOUNT OF DRY AIR
ALOFT...PRECIPITABLE WATER VALUE IS 1.90 INCHES. SEVERAL
INVERSIONS ARE PRESENT ALOFT ALONG WITH SIGNIFICANT DIRECTIONAL
AND SPEED SHEAR UP TO 500 MB...WINDS ARE OUT OF THE EAST AT THE
SURFACE AND SOUTHWEST AND WEST ALOFT.
&&
.PREV DISCUSSION... /ISSUED 540 AM CST TUE DEC 8 2009/
SHORT TERM...
..SEVERE THUNDERSTORMS WITH POSSIBLY STRONG TORNADOES POSSIBLE
AND WIDESPREAD HEAVY RAINFALL EXPECTED...
HAD A COUPLE SEVERE THUNDERSTORMS AND MANY AREAS OF WIDESPREAD
STREET FLOODING WITH LOCALIZED MORE SERIOUS FLASH FLOODING EARLIER
THIS MORNING. REFER TO THE NUMEROUS LOCAL STORM REPORTS THAT WERE
SENT. HEAVY RAIN APPEARS TO BE THE MAIN THREAT EARLY THIS
MORNING...THEN BOTH HEAVY RAIN AND SEVERE THUNDERSTORMS WILL BE
CONCERN AS WE HEAD THROUGH THE MORNING INTO THE AFTERNOON.
NUMEROUS UPPER DISTURBANCES WILL MOVE THROUGH IN THE VERY STRONG
WINDS IN THE MID AND UPPER LEVELS OF THE ATMOSPHERE. STRONG WARM
AIR ADVECTION WILL CONTINUE TO PRODUCE WIDESPREAD MODERATE TO
HEAVY RAIN WITH EMBEDDED SHOWERS AND THUNDERSTORMS WITH VERY HEAVY
RAIN. A WELL DEFINED FRONTAL BOUNDARY IS IN PLACE OVER COASTAL
SECTIONS OF SOUTH CENTRAL AND SOUTHEAST LOUISIANA. THIS BOUNDARY
SHOULD SLOWLY PUSH AND REFORM TO THE NORTH TODAY....BUT THE
WIDESPREAD RAIN TO THE NORTH OF THE BOUNDARY WILL INITIALLY RETARD
THE NORTHWARD PROGRESS. STORMS THAT DEVELOP LATER THIS MORNING
ALONG AND SOUTH OF THE BOUNDARY WILL HAVE ADEQUATE INSTABILITY AND
STRONG SHEAR TO SUPPORT A THREAT OF SEVERE THUNDERSTORMS WITH
DAMAGING WINDS AND ISOLATED TORNADOES...A FEW OF WHICH COULD BE
STRONG /EF2 OR GREATER/.
KLIX STORM TOTAL RAINFALL SHOWS WIDESPREAD VERY HEAVY AMOUNTS OF
1.5 INCHES TO 3 INCHES ALONG AND SOUTH OF I-12 FROM BATON ROUGE TO
SLIDELL...AND NORTH OF A LINE FROM MORGAN CITY TO THIBODAUX TO
JEAN LAFITTE TO YSCLOSKEY...INCLUDING THE SOUTHERN HALF OF BATON
ROUGE METRO AND ALL OF NEW ORLEANS METRO. WITHIN THIS AREA...AN
EXTENSIVE AREA OF 4 TO JUST OVER 5 INCHES IS INDICATED ACROSS
ASSUMPTION...SOUTHERN ASCENSION...ST. JAMES...ST. JOHN...AND
EXTREME NORTHWEST LAFOURCHE PARISHES. THESE AREAS WILL TAKE THE
LEAST AMOUNT OF ADDITIONAL RAIN TO PRODUCE ADDITIONAL FLOODING.
ISSUED A FLASH FLOOD WATCH TODAY FOR THE ENTIRE FORECAST AREA
EXCEPT THE LOWER SECTIONS OF THE COASTAL PARISHES.
THE COLD FRONT WILL SWEEP THROUGH THE FORECAST AREA TONIGHT AS THE
PARENT STRONG SURFACE LOW MOVES FROM THE CENTRAL PLAINS ACROSS
THE MID MISSISSIPPI VALLEY AND UPPER MIDWEST. ANYONE TRAVELING
NORTH AND WEST OF THE SURFACE LOW TRACK ACROSS WESTERN...CENTRAL
AND NORTHERN STATES TODAY AND TONIGHT SHOULD BE AWARE THERE WILL
BE A MAJOR SNOWSTORM WITH BLIZZARD CONDITIONS IN SOME AREAS.
THERE WILL BE FAIRLY LARGE TEMPERATURE GRADIENT WITH REGARDS TO
HIGHS ON WEDNESDAY DUE TO THE PROXIMITY OF THE COLD FRONT EXITING
THE SOUTHEAST AREAS. WEDNESDAY NIGHT WILL SEE COLD
TEMPERATURES...BUT CLOUD COVER SHOULD KEEP THE LOWS ABOVE FREEZING.
LONG TERM...
THE NEXT SURFACE LOW PRESSURE SYSTEM WILL COME THROUGH DURING THE
FRIDAY THROUGH SATURDAY TIME FRAME. THERE ARE SOME LOCATION AND
TIMING ISSUES TO DEAL WITH...BUT IT APPEARS THIS SYSTEM WILL ALSO
HAVE THE POTENTIAL TO PRODUCE MODERATE TO HEAVY RAINFALL. SUNDAY
SHOULD BE DRY AND BETWEEN SYSTEMS...THEN THE NEXT STORM SYSTEM IN
THIS ACTIVE PATTERN SHOULD COME THROUGH NEXT MONDAY AND
TUESDAY...AND FORECAST MODELS ARE SHOWING HEAVY PRECIPITATION AND
SOME POTENTIAL FOR SEVERE THUNDERSTORMS WITH THAT SYSTEM. 22/TD
AVIATION...
..12Z AVIATION DISCUSSION...
STRONG ISENTROPIC LIFTING OVER A STALLED OUT FRONTAL BOUNDARY WILL
CONTINUE TO BRING PERIODS OF RAIN AND THUNDERSTORMS TO THE TERMINALS
THROUGH AROUND 15Z. AS A RESULT...EXPECT PERIODS OF IFR AND
POSSIBLY LIFR CEILINGS AND VISIBILITIES WHEN BANDS OF HEAVIER SHOWERS
AND THUNDERSTORMS PULL THROUGH. WINDS WILL ALSO BE QUITE STRONG AT
15 KNOTS ARE GREAT FROM THE EAST SOUTHEAST. AFTER 15Z...THE FRONTAL
BOUNDARY IS EXPECTED TO SLIDE TO THE NORTH...ALLOWING FOR A BREAK
FROM THE HEAVIER RAINS. HOWEVER...THIS BREAK WILL BE
SHORT-LIVED...AS CONVECTION REDEVELOPS AFTER 18Z AND CONTINUES
THROUGH THE EVENING HOURS. THIS CONVECTION WILL BE DRIVEN BY AN
APPROACHING COLD FRONT. EXPECT IFR CEILINGS AND VISIBILITIES TO
CONTINUE THROUGH THE FORECAST PERIOD. 32
MARINE...
STRONG SOUTHERLY FLOW OF 20 TO 25 KNOTS AND HIGH SEAS WILL IMPACT
THE COASTAL WATERS AND TIDAL LAKES THROUGH EARLY TONIGHT. AS A
RESULT...SMALL CRAFT ADVISORIES HAVE BEEN POSTED FOR ALL AREAS. A
COLD FRONT WILL SWEEP THROUGH LATE TONIGHT...ALLOWING FOR A BRIEF
BREAK FROM THE SMALL CRAFT CONDITIONS. HOWEVER...GRADIENT FLOW IS
EXPECTED TO INCREASE BY WEDNESDAY NIGHT...WITH PERSISTENT SMALL
CRAFT CONDITIONS IN PLACE THROUGH FRIDAY NIGHT. WINDS AND SEAS
SHOULD SUBSIDE OVER THE WEEKEND...AS HIGH PRESSURE SETTLES INTO
THE REGION. 32
HYDROLOGY...
NO SPECIFICS YET ON THIS HEAVY RAINFALLS IMPACTS ON
RIVERS...HOWEVER...THERE WILL LIKELY BE SIGINIFICANT RISES ON MANY
AREA RIVERS FROM THE BATON ROUGE AREA ACROSS THE NORTHSHORE OF
LAKE PONTCHARTRAIN TO THE MISSISSIPPI GULF COAST. WILL HAVE MORE
INFORMATION ON THIS DURING THE NEXT COUPLE HOURS. 22/TD
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 73 52 59 33 / 100 70 10 10
BTR 74 56 64 36 / 90 60 10 10
MSY 74 63 69 44 / 90 70 10 10
GPT 71 61 71 39 / 100 80 20 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR LAZ034>040-
046>050-056>065-070.
GM...SMALL CRAFT ADVISORY UNTIL 3 AM CST WEDNESDAY FOR GMZ530-550-570.
SMALL CRAFT ADVISORY UNTIL 6 AM CST WEDNESDAY FOR GMZ555-575.
MS...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR MSZ068>071-077-
080>082.
GM...SMALL CRAFT ADVISORY UNTIL 3 AM CST WEDNESDAY FOR GMZ550-570.
SMALL CRAFT ADVISORY UNTIL 6 AM CST WEDNESDAY FOR GMZ575.
&&
$$
