Severe Thunderstorm Warning 85, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
330 AM CDT SAT MAY 13 2000

A MAINLY ZONAL FLOW PATTERN WILL CONTINUE ACROSS THE GULF COAST
STATES THROUGH SUNDAY. THE STRONGEST SHORTWAVE TROUGH WILL CONTINUE
TO MOVE ACROSS THE GREAT LAKES AND MID MISSISSIPPI VALLEY TODAY.
THE MAIN WEATHER MAKER FOR SE LA AND S MS IS THE COMBINATION OF A
SHORTWAVE TROUGH EXITING THROUGH THE TN VALLEY EARLY THIS MORNING...
AND THE MCS OVER MS/LA THAT THE SHORTWAVE HELPED INITIATE. A SQUALL
LINE EXTENDED ALONG THE MS RIVER FROM KTVR-KHEZ TO E OF KAEX AT 08Z
WITH A SE MOVEMENT OF 35 TO 40 KNOTS. SATELLITE AND LIGHTNING DATA
SHOW A WEAKENING OF THE CONVECTION THE LAST SEVERAL HOURS. SINCE
THIS SYSTEM IS NOW DRIVEN BY THE MESOSCALE AND ALREADY SE OF EARLIER
FORECASTS...THE ETA/NGM/AVN MODEL SUITE IS NOT HANDLING THE
SITUATION THAT WELL IN THE SHORT TERM. WOULD STILL EXPECT THE SOLID
LINE OF SHOWERS AND THUNDERSTORMS TO SCATTER OUT BY AROUND 12Z WITH
THE LINE VERY CLOSE TO A KMCB TO KBTR LINE AT THAT TIME.

LOW CONVECTIVE TEMPERATURES AND A TROPICAL AIRMASS ARE EVIDENT BY
THE ISOLATED SHOWERS THAT DEVELOPED THE LAST FEW HOURS FROM SE OF
KLFT TO NEAR KASD. THIS ACTIVITY COMBINED WITH THE APPROACHING LINE
OF SHOWERS AND THUNDERSTORMS JUSTIFIES HIGHER THAN GUIDANCE POPS
TODAY...40 TO 50 PERCENT. THE ASSOCIATED COLD FRONT...NOW HUNG UP
OVER SE AR AND EXTREME NW LA...SHOULD MAKE A SURGE SE INTO S MS AND
E CENTRAL LA THIS AFTERNOON. THE OUTFLOW BOUNDARY WILL LIKELY GET
INTO SE LA AND COASTAL MS BY LATE MORNING WHICH WILL PROVIDE A FOCUS
FOR AFTERNOON AND EARLY EVENING CONVECTION. WEAKENING DYNAMICS WITH
TIME TODAY SHOULD KEEP THE THUNDERSTORMS BELOW SEVERE LIMITS WITH
AVERAGE QPF PROBABLY IN THE .25 TO .50 INCH RANGE.

THE COLD FRONT SHOULD MOVE OFF THE COAST TONIGHT WITH DRY HIGH
PRESSURE BUILDING IN FROM THE NORTH. WILL ONLY CARRY SMALL POPS FOR
EVENING THEN THE REMAINDER OF THE FORECAST LOOKS DRY THROUGH AT
LEAST WEDNESDAY. LOWERED HUMIDITY WILL LEAD TO SOME COOLER NIGHTS
AND CLOSER TO SEASONAL HIGHS.

MCB 86/58/83/53 5200   BTR 86/61/84/57 5200
MSY 87/65/83/62 4300   GPT 86/63/84/57 4300

.NEW...NONE
LA...NONE
MS...NONE.

22

LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-131800-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1000 AM CDT SAT MAY 13 2000

THE FORECAST AREA COVERING SOUTHEAST LOUISIANA AND SOUTHERN
MISSISSIPPI REMAINS UNDER THE INFLUENCE OF A WARM AND UNSTABLE AIR
MASS.  AT THE SAME TIME...A COLD FRONT STRETCHING FROM SOUTHERN
TEXAS TOWARD NORTHWEST LOUISIANA AND NORTHWEST MISSISSIPPI IS
PUSHING TOWARD THE SOUTHEAST AND IS EXPECTED TO MOVE ACROSS THE
FORECAST AREA BY LATE THIS EVENING.  AS A RESULT...SCATTERED SHOWERS
AND THUNDERSTORMS ARE FORECAST TO BEGIN LATER THIS MORNING
LEADING INTO THE EARLY AFTERNOON HOURS AND CONTINUE THROUGH
TONIGHT.  THE PRIMARY THREAT FROM THESE THUNDERSTORMS SHOULD BE
BRIEF PERIODS OF HEAVY RAIN ALONG WITH GUSTY WINDS AND SMALL HAIL.
HOWEVER...THE THUNDERSTORM ACTIVITY IS NOT LIKELY TO REACH SEVERE
THRESHOLDS.

FOR MORE INFO PLEASE VISIT OUR WEB-SITE AT WWW.SRH.NOAA.GOV/LIX
(ALL LOWER CASE).