000
FXUS64 KLIX 032137
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
337 PM CST WED DEC 3 2008
.SYNOPSIS...
MUCH WARMER TODAY THAN YESTERDAY. SOUTHERLY WINDS HAVE HELPED
BRING WARM AND MOIST AIR BACK TO THE REGION. GENERALLY SEEING
TEMPERATURES IN THE LOW TO MID 70S ACROSS THE AREA. A TIGHTENING
PRESSURE GRADIENT HAS RESULTED IN STRONGER WINDS OF 10 TO 15 MPH
AND OCCASIONAL GUSTS IN THE 20 TO 25 MPH RANGE.
A SURFACE LOW IS LOCATED NORTH OF MICHIGAN WITH A COLD FRONT
EXTENDING SOUTHWESTWARD THROUGH ILLINOIS...MISSOURI...ARKANSAS
AND TEXAS.
&&
.DISCUSSION...
THE AFOREMENTIONED COLD FRONT WILL CONTINUE TO MOVE
SLOWLY EASTWARD AND SHOULD BEGIN TO AFFECT THE NORTHWESTERN
PORTION OF THE LOCAL AREA OVERNIGHT TONIGHT. THE BEST CHANCES OF
RAIN TONIGHT WILL GENERALLY BE NORTHWEST OF A LINE FROM TYLERTOWN
TO DONALDSONVILLE. WINDS HAVE BEEN INCREASING THROUGH THE
AFTERNOON HOURS AS THE PRESSURE GRADIENT TIGHTENS...AND ARE
FORECAST TO REMAIN AT OR SLIGHTLY ABOVE 10 MPH OVERNIGHT. THIS
SHOULD KEEP THE AIRMASS WELL MIXED...SO WILL BE FORECASTING LOW
TEMPERATURES 3 TO 5 DEGREES HIGHER THAN GUIDANCE.
BY THURSDAY MORNING...THE FRONT SHOULD BE DRAPED ACROSS THE REGION
WITH RAIN LIKELY. SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS
TIME...HOWEVER...DECENT LAPSE RATES FORECAST ABOVE 850 MB SHOULD
SUPPORT THE DEVELOPMENT OF AT LEAST SOME ELEVATED THUNDERSTORMS.
THEREFORE HAVE CONTINUED TO CARRY A CHANCE OF TRW IN THE ZONES FOR
THURSDAY.
THE FRONT SHOULD CLEAR THE AREA AND MOVE INTO THE GULF BY LATE
AFTERNOON OR EARLY EVENING THURSDAY. AS A STRONG SURFACE HIGH
BUILDS INTO THE REGION BEHIND THE FRONT...A RETURN TO BELOW NORMAL
TEMPS CAN BE EXPECTED. FORECAST TEMPERATURES ARE GENERALLY IN THE
LOW 30 TO MID 30S NORTH OF THE LAKE AND LOW 40S SOUTH OF THE LAKE
FOR FRIDAY AND SATURDAY MORNINGS...WITH HIGHS GENERALLY FORECAST
IN THE 50S TO AROUND 60 FOR BOTH AFTERNOONS.
ON SUNDAY...A REINFORCING SHOT OF COOL AND DRY AIR WILL ARRIVE AS
A BROAD UPPER TROUGH MOVES ACROSS THE REGION. MOISTURE WILL BE
VERY LIMITED AND AM NOT FORECASTING ANY PRECIP AS THIS TROUGH
MOVES THROUGH. WILL CONTINUE TO SHOW A SLIGHT COOLING TREND FROM
SATURDAY TO SUNDAY.
BY MONDAY...THE MODELS BEGIN TO DIVERGE SIGNIFICANTLY. COMPARED TO
YESTERDAY/S MODEL RUNS...THE GFS AND ECMWF APPEAR TO HAVE TRADED
ROLES. THE 12Z GFS NOW DEPICTS A MORE AMPLIFIED UPPER TROUGH THAT
TAKES ON A SLIGHTLY NEGATIVE TILT OVER CENTRAL MISSISSIPPI AND
ALABAMA. THE SURFACE LOW ASSOCIATED WITH THIS SYSTEM IS ALSO MUCH
FARTHER SOUTH AND MUCH SLOWER THAN PREVIOUSLY FORECAST. THIS
SCENARIO IS VERY SIMILAR TO THE SOLUTION FROM THE 00Z ECMWF. ON
THE OTHER HAND...THE ECMWF NOW CARRIES A BROADER AND MUCH FASTER
MOVING UPPER TROUGH...BRINGING THE FRONT THROUGH THE AREA LATE
THURSDAY EVENING OR EARLY THURSDAY NIGHT...WHICH IS A SIMILAR
SOLUTION TO THE 00Z GFS.
ONCE AGAIN...WITH LITTLE CONFIDENCE IN EITHER SOLUTION...HAVE
MADE FEW CHANGES IN THE EXTENDED PERIOD. HOWEVER...DID BUMP UP THE
POPS SLIGHTLY ON TUESDAY AS BOTH SCENARIOS INDICATE A DECENT
CHANCE OF RAIN THAT AFTERNOON. THE TEMP FORECAST FOR THIS PERIOD
IS CLOSE TO HPC GUIDANCE AND IS AN ATTEMPT AT A CONSENSUS BETWEEN
THE TWO DIFFERENT SOLUTIONS.
&&
.AVIATION...
THE INCREASED PRESSURE GRADIENT OVER THE LOWER MISSISSIPPI VALLEY
WILL LEAD TO GUSTY SOUTHERLY WINDS ACROSS THE AREA...MAINLY FOR THIS
AFTERNOON. WINDS SHOULD DECOUPLE SOMEWHAT. VFR CONDITIONS ARE
EXPECTED THROUGH 06Z TONIGHT AT ALL FOUR SITES...THEN MVFR
CONDITIONS ARE LIKELY AT KMCB AND KBTR AFTER 06-09Z THURSDAY ALONG
WITH THE LIKELIHOOD OF SHRA AND A CHANCE OF TSRA AS A LOW PRESSURE
SYSTEM AND COLD FRONT APPROACH. KMSY-KGPT SHOULD REMAIN VFR THROUGH
12Z THURSDAY...THEN CONDITIONS WILL WORSEN THROUGH THE DAY THURSDAY
AS SHRA/TSRA AND THE COLD FRONT MOVE THROUGH. IFR WEATHER WILL BE
POSSIBLE AT ALL TAF SITES THURSDAY.
&&
.MARINE...
LATEST SURFACE MAP SHOWED A 1008MB LOW OVER NORTHWEST ARKANSAS WITH
THE TIGHTEST PRESSURE GRADIENT OVER THE LOWER MISSISSIPPI VALLEY...A
12MB CHANGE FROM MOBILE BAY TO NORTHWEST LOUISIANA. MANY LAND AND
SEA SITES WINDS ACROSS THE FORECAST AREA HAVE INCREASED WINDS UP TO
17 KNOTS WITH GUSTS UP TO 24 KNOTS. ALTHOUGH WINDS MAY WEAKEN OVER
LAND TONIGHT...THE THE TIGHT PRESSURE GRADIENT IN PLACE AND MID 70S
WATER TEMPS WILL YIELD STRONG WINDS NEAR SEA SURFACE ACROSS EXTREME
NORTH AND NORTHWEST GULF. WILL ISSUE A SMALL CRAFT ADVISORY FOR WEST
OF MS RIVER AFTER MIDNIGHT. GRADIENT WEAKENS A TAD THURSDAY AND WE
ARE NOT VERY CONFIDENT OF WINDS MEETING SCA CRITERIA. ANOTHER
FRONTAL PASSAGE IS EXPECTED SATURDAY AND POSSIBLY A SMALL CRAFT
ADVISORY SATURDAY NIGHT INTO EARLY SUNDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 52 58 33 53 / 60 60 10 0
BTR 56 60 35 55 / 60 60 10 0
MSY 61 66 42 56 / 30 60 10 0
GPT 58 67 37 56 / 30 60 20 0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS FROM MIDNIGHT TONIGHT TO 6 AM CST
THURSDAY FOR GMZ550-570.
MS...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS FROM MIDNIGHT TONIGHT TO 6 AM CST
THURSDAY FOR GMZ570.
&&
$$
AVIATION/MARINE...18
REST OF DISCUSSION...95/DM
