FXUS64 KLIX 032154
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
354 PM CST THU DEC 3 2009
.SHORT TERM...
A SNOW EVENT FOR PORTIONS OF SOUTHEAST LOUISIANA AND SOUTHERN
MISSISSIPPI IS LOOKING MORE LIKELY FOR FRIDAY NIGHT. AS A
RESULT...HAVE DECIDED TO ISSUE A WINTER WEATHER WATCH FOR MOST OF
SOUTHEAST LOUISIANA NORTH OF THE I-12 CORRIDOR. THIS WATCH ALSO
EXTENDS INTO SOUTHERN MISSISSIPPI. A WINTER WEATHER ADVISORY HAS
BEEN POSTED FOR AREAS ALONG THE MISSISSIPPI COAST...DUE TO A BIT
WARMER SURFACE TEMPERATURE AND LATER START TIME FOR THE SNOW.
AFTER REVIEWING THE LATEST FORECAST GUIDANCE...SUBSTANTIAL UPPER
LEVEL FORCING IS EXPECTED TO SWEEP THROUGH THE AREA FRIDAY
NIGHT...AS A STRONG UPPER LEVEL TROUGH AXIS LIFTS TO THE NORTHEAST
THROUGH THE REGION. THIS STRONG UPPER LEVEL LIFT...COMBINED WITH
EVAPORATIVE COOLING IN THE MID-LEVELS...AS INDICATED BY THE LATEST
MODEL SOUNDINGS WILL CREATE A FAVORABLE ENVIRONMENT FOR
PRECIPITATION DEVELOPMENT STARTING TOMORROW AFTERNOON AND LASTING
THROUGH EARLY SATURDAY MORNING. THE PRECIPITATION WILL INITIALLY
FALL AS RAIN...BUT WILL BEGIN TO TRANSITION TO A WINTRY MIX OVER
NORTHWEST PORTIONS OF THE FORECAST AREA AFTER 3 PM. A SOUTHWARD
AND EASTWARD PROGRESSION OF THIS TRANSITION FROM RAIN TO A WINTRY
MIX WILL CONTINUE THROUGH THE EVENING HOURS. BY 9PM...EXPECT AN
AREA OF LIGHT TO MODERATE SNOW TO DEVELOP FROM THE BATON ROUGE
METRO AREA EASTWARD THROUGH THE NORTHERN PART OF THE FLORIDA
PARISHES. THE CHANGE OVER WILL BE DUE TO SOME STRONG MID- LEVEL
COLD AIR ADVECTION TAKING HOLD. THE 850MB ZERO DEGREE ISOTHERM
WILL DROP FROM THE NATCHEZ AREA TO THE I-10 CORRIDOR BY FRIDAY
EVENING AND REMAIN PARKED OVER THE SAME SPOT THROUGH SATURDAY
MORNING. AS A RESULT...1000-500MB THICKNESS VALUES WILL DROP TO
5400 METERS OR LOWER ACROSS THE NORTHERN HALF OF THE CWA FOR
FRIDAY EVENING AND FRIDAY NIGHT. AT THIS TIME...LEANING TOWARD A 1
TO 3 INCH ACCUMULATION...BUT AMOUNTS COULD BE HIGHER IF THE UPPER
FORCING IS STRONGER...THE AMOUNT OF MOISTURE IS GREATER...OR MORE
COOLING TAKES PLACE THAN EXPECTED.
FARTHER TO THE SOUTH...IN THE HOUMA AND SOUTHSHORE AREA...A WINTRY
MIX OF RAIN...SLEET...AND SNOW IS EXPECTED TO DEVELOP LATE FRIDAY
EVENING AND LAST THROUGH EARLY SATURDAY MORNING. AT THIS
TIME...TEMPERATURE PROFILES DO NOT SUPPORT ANY ACCUMULATING SNOW.
HOWEVER...BRIDGES AND OVERPASSES MAY DEVELOP A FEW SLICK SPOTS.
COASTAL LOUISIANA WILL SEE A COLD RAIN THROUGH THE NIGHT...BUT THE
LOW LEVEL ATMOSPHERE WILL BE TOO WARM FOR ANY WINTRY PRECIPITATION
DEVELOPMENT.
IN THE WAKE OF THIS LOW...STRONG DRY AIR ADVECTION AND SUBSIDENCE
WILL TAKE HOLD. RAPIDLY CLEARING SKIES AND COLD TEMPERATURES WILL
BE RULE SATURDAY INTO SATURDAY NIGHT.
.LONG TERM...
HEADING INTO SUNDAY AND EARLY NEXT WEEK...THE ECMWF AND GFS BOTH
ARE IN GOOD AGREEMENT THAT A MORE ZONAL AND PROGRESSIVE PATTERN
WILL DEVELOP. A FAST MOVING SHORT WAVE TROUGH WILL SWEEP THROUGH
THE AREA SUNDAY NIGHT INTO MONDAY MORNING...AND HAVE KEPT IN A
CHANCE OF RAIN FOR THIS PERIOD. A BRIEF PERIOD OF RIDGING WILL
BUILD IN BEHIND THE SYSTEM WILL DEVELOP FOR MONDAY NIGHT...BUT
ANOTHER MUCH STRONGER TROUGH WILL BEGIN TO AFFECT THE REGION ON
TUESDAY. THIS TROUGH WILL DIVE SOUTHWARD ACROSS THE
ROCKIES...CREATING A MORE AMPLIFIED PATTERN ACROSS THE CONUS BY
MID-WEEK. THIS BROAD POSITIVELY TILTED TROUGH WILL KEEP A BROAD
REGION OF LIFT IN PLACE ACROSS THE GULF COAST. IN ADDITION...DEEP
SOUTHERLY FLOW WILL DEVELOP OFF THE GULF OF MEXICO MONDAY NIGHT
AND REMAIN IN PLACE THROUGH WEDNESDAY. WARM AND HUMID
CONDITIONS...AND POSSIBLY A FEW THUNDERSTORMS ARE EXPECTED FOR
TUESDAY AND TUESDAY NIGHT. THE TROUGH AXIS WILL FINALLY BEGIN TO
LIFT OUT ON WEDNESDAY...DRIVING A STRONG COLD FRONT THROUGH THE
AREA. BOTH THE EURO AND GFS SHOW THE FRONT SLIDING THROUGH
WEDNESDAY AFTERNOON...WITH A COLD AND DRY HIGH RIDGE SETTLING IN
FOR THE END OF THE WEEK.
&&
.AVIATION...
VISIBLE SATELLITE SHOWED ERODED CLOUDS LAYER ACROSS SOUTHERN
MISSISSIPPI AND SOUTHEAST LOUISIANA. SOUTHWEST FLOW IS EXPECTED TO
LOWERS AND MIX OUT SOME OF THE LOWER LEVEL MOISTURE. AS A
RESULT...LOW CEILINGS SHOULD THIN THROUGH 21Z THIS AFTERNOON AND
CLOUD DECKS MAY DEVELOP BETWEEN 15 AND 20KFT OVERNIGHT WITH THE
FAST-MOVING SOUTHWEST FLOW. NORTH DRY FLOW MAINTAIN VFR CONDITIONS
WITH VISIBILITY OVERNIGHT AND VFR CONDITIONS WILL EXIST AT ALL TAF
SITES BETWEEN 12Z AND 18Z FRIDAY AT ALL TAF SITES. 18/FZ
&&
.MARINE...THE LOWER WIND SPEEDS IN PLACE WILL BE SHORT LIVED AS HIGH
PRESSURE STARTS TO INTERACT WITH DEVELOPING LOW PRESSURE EARLY
FRIDAY. SMALL CRAFT EXERCISE CAUTION CONDITIONS OVER THE COASTAL
WATERS TONIGHT. SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TO
DEVELOP FRIDAY AFTERNOON ACROSS COASTAL WATERS AND FRIDAY NIGHT
TIDAL LAKES AND COASTAL WATERS AS THE LOW PRESSURE AREA MOVES ACROSS
THE NORTHERN/CENTRAL GULF OF MEXICO. SUSTAINED WINDS APPROACHING 30
KNOTS FRIDAY NIGHT AND SATURDAY MORNING MAY PRODUCE WIND GUSTS TO
GALE FORCE /34 KNOTS/...BUT HAVE OPTED NOT TO ISSUE A GALE WATCH AT
THIS TIME. WINDS AND SEAS WILL LOWER BELOW SMALL CRAFT CRITERIA
AGAIN SATURDAY AFTERNOON WITH LIGHTER WINDS EXPECTED ON SUNDAY. 18/FZ
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 36 49 31 49 / 0 40 80 10
BTR 38 52 32 51 / 0 50 80 10
MSY 44 54 37 51 / 0 40 80 10
GPT 40 55 34 52 / 0 30 80 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...WINTER WEATHER ADVISORY FROM 6 PM FRIDAY TO 6 AM SATURDAY FOR
THE FOLLOWING ZONES: AND ST. TAMMANY.
WINTER STORM WATCH FROM 6 PM FRIDAY TO 6 AM SATURDAY FOR THE
FOLLOWING ZONES: ASCENSION...EAST BATON ROUGE...EAST
FELICIANA...IBERVILLE...LIVINGSTON...POINTE COUPEE...ST.
HELENA...TANGIPAHOA...WASHINGTON...WEST BATON ROUGE...AND
WEST FELICIANA.
GM...SMALL CRAFT ADVISORY FROM 9 PM FRIDAY TO 9 AM SATURDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
SMALL CRAFT ADVISORY FROM NOON FRIDAY TO NOON SATURDAY 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...WINTER STORM WATCH FROM 6 PM FRIDAY TO 6 AM SATURDAY FOR THE
FOLLOWING ZONES: AMITE...PEARL
RIVER...PIKE...WALTHALL...AND WILKINSON.
WINTER WEATHER ADVISORY FROM 6 PM FRIDAY TO 6 AM SATURDAY FOR
THE FOLLOWING ZONES: HANCOCK...HARRISON...AND JACKSON.
GM...SMALL CRAFT ADVISORY FROM 9 PM FRIDAY TO 9 AM SATURDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
SMALL CRAFT ADVISORY FROM NOON FRIDAY TO NOON SATURDAY 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.
&&
$$
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