AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
410 PM CDT MON MAR 28 2011

.SHORT TERM...FRONT PUSHED DOWN TO THE COAST WHILE CLOUDS CLEARED
OUT OVER MUCH OF THE REGION TODAY. FURTHER ACROSS THE NORTHWEST IN
OUR CWA CLOUDS DID HANG AROUND A LITTLE LONGER AND THIS HAS DRASTIC
IMPACTS ON THE TEMPS AS BTR HAS ONLY REACHED THE MID 70S AND MCB MID
60S BY 20Z. ZONAL FLOW IS STILL IN PLACE ALOFT AND WV SHOWS A RATHER
DRY AIR MASS OVER THE REGION CURRENTLY. THAT SAID THINGS SHOULD
BEGIN TO CHANGE RATHER QUICKLY OVER THE NEXT 12/24HRS.

TONIGHT...MOSTLY A QUIET NIGHT IN STORE. THE FRONT OVER THE COAST
WILL BEGIN TO DRIFT BACK TO THE NORTH TONIGHT AND BECOME MORE
DIFFUSE. WINDS WILL BE RELATIVELY LIGHT OVER THE LAND AND COULD LEAD
TO SOME LIGHT RADIATIONAL FOG OVER INLAND AREAS. CLOSER TO THE COAST
WHERE ONSHORE WINDS START TO REDEVELOP WE MAY SEE MORE MODERATE FOG
AS THIS BECOMES MORE OF A MARINE TYPE ENVIRONMENT HOWEVER...WE ARE
NOT EXPECTING AREAS OF DENSE FOG TONIGHT.

TOMORROW...INITIALLY WE WILL START OFF QUIET. AGAIN WE ARE LOOKING
FOR A STRONG S/W TO DROP SE OUT OF THE CNTRL ROCKIES INTO THE CNTRL
PLAINS LEADING TO MORE OF A SW FLOW PATTERN ALOFT. THIS WILL TAP
INTO THE ERN PAC MOISTURE AND BRING IT INTO OUR REGION BY TUE NIGHT.
IN THE LL...BROAD LOW PRESSURE OVER TX ALONG WITH AN INVERTED SFC
TROUGH STRETCHING FROM SERN TX THROUGH CNTRL LA/MS AND INTO NRN
AL WILL LEAD TO MODERATE SERLY-SRLY LL FLOW. THIS WILL GREATLY
INCREASE THE LL MOISTURE AS WELL AS THE INSTABILITY OVER THE
REGION AND ALL OF THIS COULD END UP SETTING THE STAGE FOR A ROUND
OF SEVERE WEATHER ALONG WITH HEAVY RAINFALL. INSTABILITY
PARAMETERS LOOK RATHER IMPRESSIVE FOR TOMORROW AFTN WITH
SHOWALTERS OF -4 TO -5 AND MLCAPE VALUES OF NEAR 1500 J/KG WHILE
STEEP MID LVL LAPSE RATES OF 6.5 TO 7.5C/KM AND VT OF 28C WILL BE
IN PLACE. THAT SAID THERE ARE SOME UNCERTAINTIES AND CONFIDENCE IS
LOW IN THE FCST THROUGH TUE AFTN. FIRST OFF WITH NO WELL DEFINED
DISTURBANCE PROGGED TO COME THROUGH THE CAP THAT IS EXPECTED TO BE
IN PLACE TOMORROW MORNING MAY TAKE QUITE A WHILE TO GET RID OF.
SECOND IN ADDITION TO THE LACK OF A STRONG FOCUSING MECHANISM WE
MAY HAVE TO COMPLETELY RELY ON DAY TIME HEATING TO GET THINGS
GOING. THAT SAID ISLTD TSRA ARE POSSIBLE TOMORROW AFTN BUT LOOK
FOR A BETTER CHANCE TOMORROW EVN. AS FOR MODE...WITH THE LACK OF
STRONG SHEAR DAMAGING WINDS AND LARGE HAIL(MAY BE THE BIGGEST
ISSUE DUE TO STEEP LAPSE RATES) APPEAR TO BE THE MAIN CONCERN. ONE
CAVEAT WOULD BE IF THE INVERTED TROUGH/WARM FRONT IS SLIGHTLY
FURTHER SOUTH INTO THE CWA ANY STORM THAT CROSSES THE FRONT WOULD
GET SOME LOCALIZED ENHANCEMENT AND COULD QUICKLY DROP A TORNADO AS
IT MOVES TO THE NORTH AND ACROSS THE BNDRY.

TUE NIGHT THROUGH WED...THIS IS GOING TO BE THE BUSIEST PART OF THE
FCST. FORCING REALLY INCREASES DURING THE EVN AS H5 HGHTS DROP 2DM
IN 6 HRS AND THEN DROP ANOTHER 3DM B/T 6Z AND 12Z WED. A WEAK SFC
WAVE/LOW WILL TRY TO DEVELOP OVER THE NRN GULF COAST/SRN LA AND
MOVE TO THE NE TWRDS SRN/CNTRL AL WED AFTN. THE INCREASE IN LIFT
ALOFT AND FORCING FROM THE SFC LOW SHOULD GET NUMEROUS TO
WIDESPREAD SHRA AND TSRA OVERNIGHT. INITIALLY TUE EVN THE SVR RISK
MAY STILL BE THE BIGGER ISSUE AS LIFT INCREASES A FEW MORE TSRA
WILL BE ABLE TO DEVELOP BUT AS MOISTURE INCREASES DURING THE EVN
AND HGHTS FALL EVEN FURTHER/FASTER THINGS COULD BECOME QUITE MESSY
AS WE MOVE INTO MORE OF A HEAVY RAIN THREAT. MOISTURE IS STILL
EXPECTED TO DRASTICALLY INCREASE WITH A LL JET HELPING TO
TRANSPORT H85 THETA E AIR AROUND 335K AND POSSIBLY HIGHER INTO THE
REGION. THE INCREASE IN SW FLOW ALOFT WILL ALSO AID IN THE PAC
MOISTURE TRANSPORT AND PWS COULD APPROACH 1.75 WHICH IS ALMOST 200
PERCENT OF NORMAL AFTER MIDNIGHT. AGAIN WITH THIS MUCH MOISTURE IN
PLACE AND INCREASING LIFT THINGS WILL TRANSFORM INTO MORE OF AN
MCS WITH LOCALLY HEAVY RAINFALL. IN ADDITION TO THE MOISTURE WE
WILL HAVE A COUPLED JET TO WORK WITH AND THE NOSE OF THE LL JET
RIGHT INTO OUR REGION SOME OF THESE TSRA WILL BE VERY EFFICIENT.
OVERALL WIDESPREAD 1.5 TO 2 INCHES OF RAIN STILL LOOKS LIKELY WITH
LOCALLY HIGHER AMOUNTS POSSIBLY EXCEEDING 3 INCHES AND WOULD NOT
BE SURPRISED TO SEE ISOLATED AREAS NEAR 5 INCHES.

THAT SAID THERE ARE SOME SIGNIFICANT DIFFERENCES IN THE MDLS. WE ARE
GOING CLOSER TO THE ECMWF SOLN WHICH HAS SUPPORT FROM THE
SREF/GFES/GEM. THE NAM AND GFS OPERATIONAL RUNS ARE MUCH LIGHTER
WITH THE PRECIP TUE NIGHT AND ARE HITTING A SECOND SFC LOW OVER
THE NERN GULF/SERN CONUS MUCH HARDER. THE GFS HAS BEEN ALL OVER
THE PLACE AND THE ECMWF HAS BEEN THE MORE CONSISTENT MDL ALONG
WITH INITIALIZING BETTER SO WE WILL STICK WITH IT. A LARGE AREA
OF SHRA AND TSRA WILL SLOWLY MOVE ACROSS THE CWA DURING THE
OVERNIGHT HRS AND THROUGH THE MORNING WED. THINGS SHOULD START TO
DRY OUT FROM NW TO SE WED AFTN BUT WITH MOSTLY ZONAL/SW FLOW ALOFT
THE BNDRY WILL NOT GET A STRONG PUSH SO SHRA AND ISLTD TSRA SHOULD
CONTINUE ACROSS COASTAL ZONES AND IN THE MARINE ZONES. AGAIN WITH
SOME OF THE PARAMETERS AND THE OVERALL PATTERN THAT MAY BE SETTING
UP WE COULD GET A FEW TSRA THAT COULD QUICKLY DROP QUITE A BIT OF
RAINFALL IN SHORT TIME AND LEAD TO SOME FLASH FLOODING CONCERNS.

.LONG TERM...NO CHANGES MADE TO THE EXTENDED. THE MEDIUM RANGE MDLS
REMAIN IN DECENT AGREEMENT WITH THE OVERALL PATTERN AFTER WED BUT
THERE ARE SOME MINOR DIFFERENCES IN THE SENSIBLE WEATHER FOR OUR
AREA WED NIGHT AND THU BUT OVERALL THINGS HAVEN`T CHANGED FOR
EARLIER THINKING WITH THE END OF THE WEEK AND INTO NEXT WEEKEND.
PREVIOUS LONG TERM PORTION HAS BEEN APPENDED. /CAB/

PREVIOUS LONG TERM DISCUSSION...THE MODELS ARE IN BETTER AGREEMENT
SHOWING A MUCH WEAKER AND BROAD SHORTWAVE TROUGH MOVING ACROSS THE
CENTRAL GULF COAST WEDNESDAY NIGHT AND THURSDAY WITH LARGER SCALE
AMPLIFICATION OF THE UPPER TROUGH OVER THE EASTERN STATES THURSDAY
NIGHT INTO FRIDAY. THE COLD FRONT IS LIKELY TO BE NEAR THE COAST OR
JUST OFFSHORE BY MIDDAY ON WEDNESDAY AS THE BEST LIFT FROM UPPER
DYNAMICS MOVE QUICKLY EAST OF THE FORECAST AREA. IT NOW APPEARS ANY
LEFTOVER STRONG TO SEVERE THUNDERSTORM AND HEAVY RAIN THREAT WILL BE
IN MAINLY COASTAL SECTIONS WEDNESDAY MORNING BEFORE MOST OF THE RAIN
ENDS FROM THE NORTHWEST WEDNESDAY AFTERNOON. ANY SECONDARY SURFACE
LOW PRESSURE DEVELOPMENT IS NOW EXPECTED TO BE WEAK...BUT PVA FROM
THE SHORTWAVE TROUGH AND ISENTROPIC LIFT SHOULD CAUSE SCATTERED
SHOWERS AND ISOLATED ELEVATED THUNDERSTORMS TO DEVELOP BACK NORTH
ACROSS THE AREA WEDNESDAY NIGHT BEFORE QUICKLY MOVING EAST WITH THE
MID LEVEL TROUGH AXIS EARLY THURSDAY MORNING.

COOLER AND DRIER AIR WILL FINALLY REPLACE THE WARM AND MUGGY
CONDITIONS BY LATE WEDNESDAY INTO THURSDAY AS HIGH PRESSURE
GRADUALLY BUILDS INTO THE AREA...BUT THURSDAY LOOKS TO BE THE ONLY
BELOW NORMAL TEMPERATURE DAY. SURFACE HIGH PRESSURE AND NORTHWEST
FLOW ALOFT WILL MAINTAIN THE DRY AND MILD WEATHER FRIDAY...THEN
TEMPERATURES WILL RETURN ABOVE NORMAL FOR THE WEEKEND AS THE
AIRMASS MODIFIES AND WARMS. THE NEXT RAIN CHANCE LOOKS TO COME
ABOUT TUESDAY OF NEXT WEEK. 22/TD

&&

.AVIATION...
CURRENT VFR CONDITIONS SHOULD CONTINUE FOR THE REMAINDER OF THE
AFTERNOON. ISOLATED SHOWERS CURRENTLY ALONG THE STATIONARY FRONT
NEAR HAMMOND. HAVE TEMPO SHRA IN FORECAST...AND WILL HOLD OFF ON
CONVECTIVE MENTION UNTIL WE ACTUALLY SEE ENOUGH CONVECTIVE
DEVELOPMENT TO MERIT SUCH. AFTER SUNSET WITH THE BOUNDARY IN THE
AREA...ANTICIPATE REDEVELOPMENT OF MVFR CIGS BEFORE MIDNIGHT...AND
IFR CEILINGS AND/OR VSBYS AROUND 08-09Z. EXPECT IMPROVEMENT TO MVFR
CIGS BY MID MORNING MONDAY. /35/

&&

.MARINE...WINDS WILL BE LIGHT TONIGHT BUT LOOK FOR ONSHORE FLOW TO
REDEVELOP EARLY TOMORROW MORNING. THERE MAY EVEN BE SOME LIGHT FOG
ALONG THE COASTAL ZONES DURING THE MORNING HRS BUT OVERALL NOT
EXPECTING MUCH OF A FOG ISSUE. WINDS WILL BEGIN TO PICK UP OUT OF
THE SE AS LOW PRESSURE STARTS TO SLOWLY DEEPEN IN ERN TX AND MORE SO
TUE NIGHT WITH THE SFC LOW EXPECTED TO MOVE ACROSS SRN LA. THAT SAID
NOT LOOKING FOR SCY CONDITIONS WITH WINDS MOSTLY IN THE 15-20 KT
RANGE OVERNIGHT TUE AND INTO WED. SEAS ARE ONLY EXPECTED TO TOP OUT
AT 5 FT. WINDS WILL TEMPORARILY GO BACK TO OFFSHORE OVERNIGHT WED
AND EARLY THU BUT WINDS WILL ONCE AGAIN BECOME LIGHT AS ANOTHER SFC
LOW TRIES TO DEVELOP OVER THE NERN GULF SERN CONUS THU AND ONCE THIS
MOVES TO THE NE THU NIGHT THE FRONT WILL FINALLY PUSH ALL THE WAY
INTO THE GULF WITH NW FLOW OVER THE COASTAL WATERS OVERNIGHT THU.
SHRA AND TSRA WILL BE IN ISSUE WED AND THROUGH THU BUT THINGS SHOULD
QUIET DOWN THU NIGHT. /CAB/