FXUS64 KLIX 011411
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
811 AM CST TUE DEC 1 2009
.UPDATE...
...SOUNDING DISCUSSION...
SECOND RELEASE REQUIRED DUE TO SIGNAL LOSS. OTHERWISE...NO
PROBLEMS WITH THE SECOND LAUNCH. MOISTURE INCREASING IN THE UPPER
LEVELS...HOWEVER VERY DRY AIR BELOW 600 MILLIBARS WITH A PW OF
1.05 INCHES. A VERY STRONG INVERSION AROUND 950 MILLIBARS WHERE
THE TEMPERATURE IS IN UPPER 50S VERSES TEMPERATURES IN THE MIDDLE
40S AT THE SURFACE. WINDS ARE BREEZY FROM THE NORTHEAST AT THE
SURFACE WITH A STRONG 124 KNOT WESTERLY JET AROUND 185 MILLIBARS.
&&
.PREV DISCUSSION... /ISSUED 447 AM CST TUE DEC 1 2009/
SHORT TERM...
COLD FRONT MOVED THROUGH THE FA AND INTO THE GULF MEXICO YESTERDAY
EVENING. THIS BOUNDARY IS NOW STALLED INTO THE NORTHERN GULF.
OVERRIDING MOISTURE FROM THE SW IS RESULTING IN GOOD RAINFALL
COVERAGE ACROSS LA COASTAL PARISHES. MOST OF THIS RAIN IS QUITE
LIGHT BUT THERE ARE A FEW EMBEDDED AREAS OF MODERATE RAIN JUST
OFFSHORE.
SFC ANALYSIS SHOWS ARE OF LOW PRESSURE HAS DEVELOPED IN THE WESTERN
GULF HAS IS BEGINNING TO DEEPEN. AS THE SURFACE RIDGE TO THE NE OF
THE AREA SHIFTS EASTWARD AND UPPER LOW OVER NORTHERN MEXICO MOVES
EASTWARD...THIS GULF LOW WILL TRACK NEWD TOWARDS THE LA COAST. THE
RAIN SHIELD WILL PROGRESSIVELY SPREAD NORTHWARD TODAY WITH THE BULK
OF THE SH/TS ACTIVITY ALONG THE SOUTHEASTERN HALF OF THE CWA. THE
TWO MAIN CONCERNS ARE HEAVY RAINFALL AND STRONG TO SEVERE
THUNDERSTORMS. FLASH FLOOD WATCH HAS BEEN EXPANDED SLIGHTLY
NORTHWARD TO ACCOUNT FOR A SLIGHTLY MORE NORTHERLY TRACK OF THE SFC
LOW. 2 TO 4 INCHES OF RAIN WILL BE POSSIBLE IN THIS AREA TODAY. AS
THE GULF LOW MOVES TOWARDS THE COAST...AN ASSOCIATED WARM FRONT WILL
ALSO BE LIFTING NORTHWARD IN THE EVENING AND OVERNIGHT HOURS.
INSTABILITY PARAMETERS ARE NOT EXPECTED TO BE VERY IMPRESSIVE BUT
SUFFICIENT. STRONG AND DEEP LAYER SHEAR IS EXPECTED TO BE IN PLACE
WHICH WILL ENHANCE THE POTENTIAL FOR SUPERCELLS TO FORM. THE MAIN
THREATS WILL BE TORNADOES/WATERSPOUTS AND DAMAGING WINDS. EXPECT
THIS THREAT TO BE ALONG AND SOUTHEAST OF A BTR TO MCB LINE WITH THE
GREATEST THREAT FROM HOU TO NEW TO ASD TO PQL AND SOUTHWARD INTO THE
COASTAL WATERS.
LONG TERM...
THE SURFACE LOW WILL BE INTO SOUTH CENTRAL MS BY DAY BREAK WED PER
ECMWF...THE MODEL PREFERENCE FOR THIS EVENT. A BAND OF MODERATE TO
HEAVY RAIN WILL LIKELY STILL EXIST ALONG THE EASTERN HALF OF THE
FORECAST AREA. THE LOW AND NOW ASSOCIATED COLD FRONT WILL QUICKLY
MOVE EASTWARD DURING THE DAY. TEMPS WILL REMAIN WELL BELOW NORMAL
WED AS NORTHERLY WINDS CONTINUE.
DEEP TROUGH WILL DIG SOUTHWARD THROUGH THE END OF THIS WEEK. COLD AIR
ADVECTION WILL CONTINUE AND MID 50S HIGHS WILL PERSIST. GFS SHOWS A
SURFACE LOW DEVELOPING IN THE NORTHERN GULF FRIDAY NIGHT AT THE SAME
TIME THAT THE BASE OF THE TROUGH REACHES THE AREA. THIS SCENARIO IS
TYPICAL OF THE WINTRY PRECIP TYPE...ESP WITH SUCH LOW THICKNESSES.
AT THIS TIME...NOT HOLDING ANY MERIT TO THIS SOLUTION AS IT IS AN
OUTLIAR AMONG OTHERS AND QUITE UNLIKELY FOR THIS TIME OF YEAR. THE
ECMWF SOLUTION LOOKS MUCH MORE APPROPRIATE WITH CONTINUED RIDGING
WELL INTO THE GULF AND THE POTENTIAL FOR A COLD LIGHT RAIN.
A ZONAL PATTERN WILL THEN DEVELOP OVER THE AREA LATE THIS WEEKEND
AND INTO EARLY NEXT WEEK. RAIN CHANCES MAY RETURN AS THE SFC RIDGE
SLIDES EAST AND SOUTHERLY FLOW FINALLY RETURNS.
MEFFER
AVIATION...
MVFR CEILINGS...CURRENTLY OVER A COUPLE COASTAL LOCATIONS OF
SOUTHEAST LOUISIANA...WILL DEVELOP AS RAIN MOVES INTO KMSY THIS
MORNING...KBTR AND KGPT DURING THE EARLY TO MID AFTERNOON
HOURS...AND KMCB THIS EVENING. ALL TAF LOCATIONS ARE EXPECTED TO
DETERIORATE TO IFR TONIGHT AS CIGS CONTINUE TO LOWER AND RAIN
INTENSIFIES. THERE IS A CHANCE OF BRIEF THUNDERSTORMS MAINLY
TONIGHT...BUT WILL NOT INCLUDE MENTION IN THE FORECAST AT THIS TIME.
THE STRONGEST WINDS WILL BE AT KMSY AND KGPT WITH FREQUENT GUSTS
ABOVE 20 KNOTS TODAY AND ESPECIALLY TONIGHT AND WEDNESDAY AS LOW
PRESSURE PASSES THROUGH THE REGION. 22/TD
MARINE...
LOW PRESSURE IN THE NORTHWEST GULF OF MEXICO TONIGHT IS FORECAST TO
STRENGTHEN AND MOVE NORTHEAST INTO SOUTH LOUISIANA AND SOUTHEAST
MISSISSIPPI LATE TODAY THROUGH EARLY WEDNESDAY MORNING. WINDS ARE
EXPECTED TO CONTINUE TO GRADUALLY INCREASE AS THIS FEATURE
APPROACHES...AND CONFIDENCE IS HIGH THAT FREQUENT GUSTS ABOVE GALE
FORECAST /34 KNOTS/ WILL DEVELOP ACROSS THE COASTAL WATERS THIS
AFTERNOON AND CONTINUE THROUGH WEDNESDAY EVENING EVEN AS THE LOW
PULLS WELL AWAY FROM THE AREA. HAVE CONVERTED THE GALE WATCH TO A
GALE WARNING AND HAVE EXTENDED THE ENDING TIME TO 10 PM WEDNESDAY.
IN ADDITION TO STRONG WINDS...STRONG TO POSSIBLY SEVERE
THUNDERSTORMS ARE LIKELY TO DEVELOP OVER THE COASTAL WATERS THROUGH
WEDNESDAY MORNING.
OVER THE LAKES...OCCASIONAL GUSTS NEAR GALE FORCE MAY DEVELOP
TONIGHT...BUT IN GENERAL SUSTAINED WINDS WILL BE MOSTLY IN THE 20 TO
25 KNOTS RANGE THIS AFTERNOON THROUGH WEDNESDAY WHEN A SMALL CRAFT
ADVISORY WILL BE IN EFFECT. 22/TD
COASTAL FLOODING...
TIDES REMAIN NEAR NORMAL/PREDICTED VALUES AT THIS TIME...BUT THAT
WILL CHANGE AS WINDS BECOME MORE EAST AND SOUTHEAST AND INCREASE
THROUGH THIS EVENING. SINCE THIS WILL BE A SHORT DURATION OF STRONG
ONSHORE WINDS...TIDES SHOULD NOT BE MORE THAN ABOUT 2 FEET ABOVE
NORMAL/PREDICTED VALUES. STILL...WITH THE 2 TO 3 FOOT ASTRONOMICAL
TIDE RANGES...THE WATER LEVELS SHOULD RISE TO LEVELS THAT CAUSE
NUISANCE FLOODING OF THE TYPICAL FLOOD PRONE LOW LYING AREAS AND
ROADS OUTSIDE OF HURRICANE PROTECTION LEVEES TONIGHT. HAVE CANCELLED
THE COASTAL FLOOD WATCH AND REPLACED IT WITH A COASTAL FLOOD
ADVISORY LATE THIS AFTERNOON THROUGH TONIGHT. ALSO REMOVED A FEW OF
THE SOUTH SHORE LAKE PONTCHARTRAIN PARISHES SINCE THE EAST WINDS
WILL BECOME SOUTH AND PUSH ANY HIGHER WATER TOWARDS THE NORTH SHORE
TONIGHT. 22/TD
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 53 47 55 36 / 70 80 40 10
BTR 55 48 58 39 / 70 80 40 10
MSY 58 53 64 44 / 90 90 40 10
GPT 58 54 63 41 / 90 100 70 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...COASTAL FLOOD ADVISORY FROM 3 PM TUESDAY TO 6 AM WEDNESDAY FOR
THE FOLLOWING ZONES: LOWER JEFFERSON...LOWER
LAFOURCHE...LOWER PLAQUEMINES...LOWER ST. BERNARD...LOWER
TERREBONNE...ORLEANS...ST. TAMMANY...AND UPPER ST. BERNARD.
FLASH FLOOD WATCH FROM 6 PM TUESDAY TO NOON WEDNESDAY FOR THE
FOLLOWING ZONES: ASSUMPTION...LOWER JEFFERSON...LOWER
LAFOURCHE...LOWER PLAQUEMINES...LOWER ST. BERNARD...LOWER
TERREBONNE...ORLEANS...ST. CHARLES...ST. JAMES...ST. JOHN
THE BAPTIST...ST. TAMMANY...UPPER JEFFERSON...UPPER
LAFOURCHE...UPPER PLAQUEMINES...UPPER ST. BERNARD...AND
UPPER TERREBONNE.
GM...SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 9 PM WEDNESDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
GALE WARNING FROM NOON TUESDAY TO 9 PM WEDNESDAY FOR THE
FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO THE
SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
NM...COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST
PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA FROM 20 TO 60 NM...AND COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL NOON TUESDAY FOR THE FOLLOWING ZONES:
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL WATERS
FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE MISSISSIPPI
RIVER OUT 20 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER TO LOWER ATCHAFALAYA RIVER LA FROM 20
TO 60 NM...AND COASTAL WATERS FROM THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER TO LOWER ATCHAFALAYA RIVER LA OUT 20
NM.
MS...FLASH FLOOD WATCH FROM 6 PM TUESDAY TO NOON WEDNESDAY FOR THE
FOLLOWING ZONES: HANCOCK...HARRISON...JACKSON...AND PEARL
RIVER.
COASTAL FLOOD ADVISORY FROM 3 PM TUESDAY TO 6 AM WEDNESDAY FOR
THE FOLLOWING ZONES: HANCOCK...HARRISON...AND JACKSON.
GM...SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 9 PM WEDNESDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
GALE WARNING FROM NOON TUESDAY TO 9 PM WEDNESDAY FOR THE
FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO THE
SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
NM...COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST
PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA FROM 20 TO 60 NM...AND COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL NOON TUESDAY FOR THE FOLLOWING ZONES:
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL WATERS
FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE MISSISSIPPI
RIVER OUT 20 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER TO LOWER ATCHAFALAYA RIVER LA FROM 20
TO 60 NM...AND COASTAL WATERS FROM THE SOUTHWEST PASS OF
THE MISSISSIPPI RIVER TO LOWER ATCHAFALAYA RIVER LA OUT 20
NM.
&&
$$
