000
FXUS64 KLIX 280943
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
343 AM CST TUE DEC 28 2010
.SHORT TERM...
DEEP LAYER RIDGING WILL DOMINATE THE REGION TODAY...ALLOWING FOR
SOME MODERATION IN TEMPERATURES AS THE DAY PROCEEDS.
HOWEVER...INITIALLY A VERY COLD AIRMASS WILL ALLOW FOR BELOW
FREEZING CONDITIONS EARLY THIS MORNING ACROSS THE ENTIRE FORECAST
AREA. LIGHTER WINDS TONIGHT HAVE ALLOWED FOR MORE RADIATIONAL
COOLING...WITH THE COLDEST READINGS OF THE YEAR IN SEVERAL
LOCATIONS BEING RECORDED TONIGHT. DUE TO THESE COLD CONDITIONS...A
FREEZE AND HARD FREEZE WARNING CONTINUE THROUGH THE MID-MORNING
HOURS. BY THE AFTERNOON HOURS...SOME WEAK WARM AIR ADVECTION WILL
BEGIN TO TAKE HOLD...ALLOWING TEMPERATURES TO CLIMB INTO THE
MIDDLE 50S. THESE READINGS ARE SIGNIFICANTLY WARMER...BUT STILL A
GOOD 5 TO 10 DEGREES BELOW NORMAL.
THE PATTERN WILL CONTINUE TO TRANSITION TO A WARMER AND MORE HUMID
SCENARIO FOR THE REGION AS THE WORK WEEK CONTINUES. A STRONG SHORT
WAVE TROUGH WILL SWING OUT OF THE FOUR CORNERS AND INTO THE
SOUTHERN PLAINS LATE TODAY INTO TONIGHT. AS THE SHORT WAVE PULLS
TO THE EAST...DEEPER SOUTHERLY FLOW OFF THE GULF OF MEXICO WILL
DEVELOP OVER TEXAS AND WESTERN LOUISIANA. THIS DEEPER MOISTURE
SHOULD BEGIN TO SPREAD INTO THE CWA LATER TONIGHT. IN ADDITION TO
THE MOISTURE...AN INCREASE IN PVA AND THUS OVERALL LIFT IN THE
UPPER LEVELS WILL ALSO SPREAD INTO THE REGION. THIS WILL MANIFEST
ITSELF IN THE FORM OF SCATTERED SHOWERS DEVELOPING OVER WESTERN
PORTIONS OF THE CWA BY WEDNESDAY AFTERNOON.
THE SHORT WAVE WILL TAKE ON A MORE NEGATIVE TILT HEADING INTO
WEDNESDAY NIGHT...ALLOWING FOR EVEN MORE FORCING ALOFT. IN
ADDITION...DYNAMICS BECOME A BIT MORE FAVORABLE TO SUPPORT DEEPER
CONVECTION...AS A 100 KNOT JET STREAK MOVES THROUGH THE GULF
SOUTH. WITH AN INCREASED SHEAR PROFILE IN PLACE...AND SOMEWHAT
BETTER THERMODYNAMIC SUPPORT...SOME ELEVATED STRONGER CONVECTION
CANNOT BE RULED OUT WEDNESDAY NIGHT. FORTUNATELY...THE CONVECTION
SHOULD NOT BE SURFACE BASED...AS A WEDGE OF COOLER AIR REMAINS IN
PLACE IN THE LOW LEVELS.
.LONG TERM...
A BRIEF PERIOD OF SUBSIDENCE ASSOCIATED WITH SOME WEAK NEGATIVE
VORTICITY ADVECTION IN THE WAKE OF THE EXITING SHORT WAVE TROUGH
AXIS WILL SPREAD INTO THE REGION THURSDAY INTO THURSDAY NIGHT.
EXPECT SOME LINGERING CONVECTION OVER THE EASTERN ZONES THURSDAY
MORNING...BUT CONDITIONS WILL SHOULD STABILIZE CONSIDERABLY BY
THURSDAY AFTERNOON. EVEN THOUGH SOME SUBSIDENCE WILL BE IN
PLACE...DO NOT EXPECT CLOUD COVER TO REDUCE MUCH THURSDAY INTO
THURSDAY...WITH PARTLY TO MOSTLY CLOUDY CONDITIONS CONTINUING.
THIS IS MAINLY DUE TO SOUTHERLY FLOW CONTINUING IN THE LOW TO MID
LEVELS OF THE ATMOSPHERE. IN ADDITION...WITH SINKING AIR IN PLACE
ALOFT AND WARMER AIR MOVING IN FROM THE GULF OF MEXICO...EXPECT
TEMPERATURES TO RISE ABOVE NORMAL ON THURSDAY AND REMAIN THAT WAY
THROUGH FRIDAY. HIGHS SHOULD RISE INTO THE LOWER TO MIDDLE 70S
EACH DAY...WITH LOWS ONLY DROPPING INTO THE UPPER 50S AND LOWER
60S. THESE READINGS WILL BE A GOOD 10 DEGREES ABOVE NORMAL.
OVERALL...THE ATMOSPHERE WILL BECOME PROGRESSIVELY MORE UNSTABLE
ON FRIDAY...AND THIS TREND WILL CONTINUE INTO SATURDAY. LIFTED
INDICES WILL RANGE FROM -2 TO -4 AND CAPE VALUES WILL INCREASE TO
AROUND 1500 J/KG FRIDAY AFTERNOON. IN ADDITION...MODEL SOUNDINGS
SHOW THAT MID-LEVEL LAPSE RATES BECOME MORE FAVORABLE FOR DEEPER
AND THUS STRONGER CONVECTION FRIDAY AFTERNOON INTO FRIDAY NIGHT.
DUE TO THESE IMPROVED THERMODYNAMIC VARIABLES...AND AN EXPECTED
INCREASE IN UPPER LEVEL FORCING ASSOCIATED WITH A DEEP LAYER
TROUGH EJECTING OUT OF THE ROCKIES AND INTO THE PLAINS
STATES...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL
IMPACT THE REGION FOR NEW YEARS EVE. A FEW OF THESE THUNDERSTORMS
COULD BE LOCALLY STRONG TO SEVERE...WITH THE MAIN CONVECTIVE MODE
LOOKING TO BE LINEAR IN NATURE...GIVEN THE UNIDIRECTIONAL NATURE
OF THE WIND FIELD IN THE MID-UPPER LEVELS.
SATURDAY NIGHT THROUGH MONDAY...THE MODELS BEGIN TO DIVERGE A BIT.
ALL OF THE MODELS SHOW A STRONG COLD FRONT ASSOCIATED WITH A
SURFACE LOW MOVING INTO THE MIDWEST AND NORTHEAST PULLING THROUGH
THE AREA SATURDAY MORNING. HOWEVER...THE EURO AND GEM BOTH PUSH
THE FRONT WELL OFFSHORE BY SATURDAY NIGHT...WHILE THE GFS STALLS
THE FRONT OVER THE COASTAL WATERS. THE REASON FOR THIS DIFFERENCE
IS THE EVOLUTION OF THE MAIN LONGWAVE TROUGH OVER THE PLAINS AND
WESTERN STATES. ALL OF THE MODELS KEEP A POSITIVELY TILTED TROUGH
AXIS IN PLACE...BUT THE EURO IS MUCH WEAKER WITH THE TROUGH AND
ACTUALLY HAS SOME RIDGING DEVELOPING OVER THE INTER-MOUNTAIN
REGION. THE GFS IS STRONGER WITH THE TROUGH AND HAS THE TROUGH
REMAINING IN PLACE THROUGH THE FOUR CORNERS AND CALIFORNIA. HAVE
DECIDED TO LEAN TOWARD THE GFS IN THE EXTENDED...BUT THE FORECAST
IS DEFINITELY A LOW CONFIDENCE ONE.
WITH THE GFS AS A BASELINE...KEEP CLOUDS AND SHOWERS IN PLACE OVER
THE COASTAL WATERS AND COASTAL PARISHES ON SUNDAY. HOWEVER...A
WEAK IMPULSE WILL SLIDE OUT OF THE FOUR CORNERS AND INSTIGATE SOME
CYCLOGENESIS IN A REGION OF ENHANCED BAROCLINICITY OVER THE
WESTERN GULF OF MEXICO SUNDAY NIGHT INTO MONDAY. A SURFACE LOW
WILL PASS ALONG THE FRONT AND SWEEP THROUGH THE REGION ON MONDAY.
ISENTROPICALLY INDUCED PRECIPITATION SHOULD DEVELOP ACROSS THE CWA
ON MONDAY AND LINGER INTO TUESDAY AS THE LOW MOVES THROUGH THE
GULF OF MEXICO AND INTO THE SOUTHEAST. HAVE WENT WITH CHANCE POPS
FOR MONDAY AND TUESDAY TO REFLECT THIS.
&&
.AVIATION...
VFR CONDITIONS THIS MORNING WITH SOME INVADING ALTOSTRATUS FROM THE
WEST LIKELY TO MOVE INTO KBTR AND KMCB LATER THIS MORNING. LEADING
EDGE IS BASED AROUND 4KFT-5KFT...LOWERING TO MVFR CEILINGS IN EAST
TEXAS. 24/RR
&&
.MARINE...
LIGHT WINDS AND LOW SEAS EXPECTED FOR THE NEXT 24 HOURS BEFORE AN
ABRUPT INCREASE IN CONDITIONS DUE TO LONG FETCHED RETURN FLOW
WEDNESDAY FROM WEST TO EAST. AN UPPER LEVEL DISTURBANCE ALSO
EXPECTING TO INCREASE GUSTINESS OVER THE COASTAL WATERS AND PROVIDE
SOME ELEVATED BASES CONVECTION WEDNESDAY NIGHT INTO EARLY THURSDAY.
NEXT COLD FRONT WILL BE SLOWING FORWARD PROGRESS UPON ARRIVING INTO
SE LA COASTAL WATERS THIS WEEKEND...BUT BE CLOSE ENOUGH TO ENHANCE
SOUTHWEST WINDS AT EXERCISE CAUTION TO ADVISORY LEVELS FROM FRIDAY
THROUGH SUNDAY. LONG PERIOD SWELLS FROM LOWER GULF AND FLORIDA
STRAITS WILL ALSO BE A CONCERN WEDNESDAY ONWARD. 24/RR
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 57 35 62 52 / 10 10 40 70
BTR 59 38 66 56 / 10 10 40 70
ASD 57 36 63 54 / 0 10 30 70
MSY 57 42 66 58 / 0 10 30 70
GPT 56 34 62 55 / 0 10 20 70
PQL 56 32 63 52 / 0 10 20 70
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FREEZE WARNING UNTIL 9 AM TUESDAY 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...UPPER JEFFERSON...UPPER LAFOURCHE...UPPER
PLAQUEMINES...UPPER ST. BERNARD...AND UPPER TERREBONNE.
HARD FREEZE WARNING UNTIL 9 AM TUESDAY FOR THE FOLLOWING ZONES:
ASCENSION...EAST BATON ROUGE...EAST
FELICIANA...IBERVILLE...LIVINGSTON...POINTE COUPEE...ST.
HELENA...ST. TAMMANY...TANGIPAHOA...WASHINGTON...WEST BATON
ROUGE...AND WEST FELICIANA.
GM...NONE.
MS...HARD FREEZE WARNING UNTIL 9 AM TUESDAY FOR THE FOLLOWING ZONES:
AMITE...HANCOCK...HARRISON...JACKSON...PEARL
RIVER...PIKE...WALTHALL...AND WILKINSON.
GM...NONE.
&&
$$
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