Severe Thunderstorm Warning 34, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1005 AM CST WED MAR 29 2000

...SEVERE THUNDERSTORM THREAT STILL A GO...

WILL UPDATE ZONES TO REMOVE MORNING CONDITIONS ONLY BUT ALL ELSE IS
VERY MUCH ON TRACK.

12Z ANALYSES INDICATE SUB-TROPICAL JET ACROSS LA WITH A 110KT
MAXIMUM NEAR THE SABINE RIVER. THE POSITION OF THIS JET STRUCTURE
SHOULD PLACE S LA AND S MS IN THE RIGHT REAR QUADRANT BY THIS
AFTERNOON.  925MB THETAE RIDGE RUNNING WNW-ESE FROM TOLEDO BEND TO
NEW ORLEANS AREA. 850MB THETAE TROUGH IN PLACE FROM THE ATLANTIC
INTO SE LA WILL BE ERODING RAPIDLY WITH LOW LEVEL SLY FLOW OF
25-35KTS. EXPECTING LOW LEVEL THETAE VALUES TO RAMP QUICKLY TO ABOUT
335-337K RANGE. SURFACE DEWPOINTS ALREADY IN THE LOWER 70S ACROSS
THE COASTAL PARISHES.

12Z SOUNDING SHOWS STEEP LAPSE RATE WITH WET BULB ZERO AROUND 9KFT.
HODOGRAPH IS QUITE ALARMING WITH A SPLITTING SUPERCELL PROFILE AND
HELICITY VALUES IN THE 270 M2/S2 RANGE AND CAPES TO APPROACH 2500
J/KG THIS AFTERNOON. SOUNDING ALSO EXHIBITS DRY MICROBURST
CHARACTERISTICS WITH A MOIST MID-LAYER TOPPED BY VERY DRY AIR ALOFT.

USING PCPN CALCULATOR/RICKS INDEX TECHNIQUE ON MODIFIED SIL SOUNDING
FOR 337K LIFT FROM 900MB...POP = 92%...PCPN 3.88"...POTL PCPN
7.60"...FMAP 3.91"...RICKS INDEX 163...PROB OF SVR = 6% BUT AS HIGH
AS 20% IF 337K REACHES 850MB...FCST GUSTS 54 TO 64 KTS...HAIL POTL
UP TO 2" DIAMETER AND MODERATE TOR RISK TO F4 STRENGTH POSSIBLE.

WE HAVE BEEN AUTHORIZED FOR A SPECIAL 18Z BALLOON RELEASE. SOUNDING
DATA SHOULD BE AVAILABLE BY 1230 PM. ALSO...NCEP WILL BE OPERATING
GOES 8 IN RSO OPERATIONS WHICH MEANS GREATER TEMPORAL RESOLUTION ON z
SATELLITE IMAGERY DURING THE EVENT. THE THUNDERSTORM OUTLOOK WILL
FEATURE HEAVY WORDING TO HIGHLIGHT THE THREAT.

.NEW...NONE.
LA...NONE.
MS...NONE.
24

LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-292300-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1040 AM CST WED MAR 29 2000

...SEVERE THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND TONIGHT...

THERE IS A MODERATE RISK FOR SEVERE THUNDERSTORMS TO DEVELOP ACROSS
SOUTH LOUISIANA AND SOUTH MISSISSIPPI THROUGH TONIGHT. A LOW
PRESSURE SYSTEM IN NORTHEAST TEXAS WILL BE MOVING SOUTHEAST INTO
THE SOUTH-CENTRAL PARISHES EARLY THIS AFTERNOON. INCREASING
SOUTHERLY FLOW WITH HIGHER DEWPOINT AIR WILL DESTABILIZE THE AIRMASS
ACROSS THE FORECAST AREA THIS AFTERNOON. WITH DAYTIME TEMPERATURES
WARMING INTO THE LOWER AND MID 80S...THUNDERSTORMS WILL BE CAPABLE
OF DEVELOPING RAPIDLY. THE PREVAILING MOVEMENT OF THE THUNDERSTORMS
WILL BE TOWARDS THE EAST AT 40 TO 50 MPH.

THE PRIMARY SEVERE WEATHER THREAT WILL BE DAMAGING WIND GUSTS IN
EXCESS OF 60 MPH...LARGE HAIL POSSIBLY AS LARGE AS GOLFBALL TO
BASEBALL SIZE...AND ISOLATED TORNADOES. LOCALLY HEAVY RAINFALL AND
FREQUENT LIGHTNING WILL ALSO ACCOMPANY ANY THUNDERSTORMS. THE
ONSET OF THE THUNDERSTORMS IS EXPECTED TO OCCUR AROUND NOON ALONG THE
ATCHAFALAYA BASIN AND SPREAD EASTWARD INTO THE GREATER NEW ORLEANS
AREA BY 3 PM...CONTINUING INTO THE MISSISSIPPI COASTAL COUNTIES BY 5
PM. THE SEVERE WEATHER THREAT MAY CONTINUE THROUGH MIDNIGHT TONIGHT.

LAW ENFORCEMENT AND EMERGENCY PREPAREDNESS OFFICIALS ARE
URGED TO STAFF ACCORDINGLY FOR THIS POTENTIALLY HAZARDOUS
SITUATION. STORM SPOTTERS SHOULD BE ACTIVATED FOR THIS AFTERNOON
ALONG WITH HAM RADIO OPERATOR NETWORKS.

STAY TUNED TO LOCAL AND CABLE TV...RADIO AND NOAA WEATHER RADIO
BROADCAST FOR THE LATEST WATCHES AND WARNINGS THAT MAY BE ISSUED
THROUGHOUT THE DAY. PERSONS SHOULD TAKE THIS TIME TO REVIEW
EMERGENCY PLANS AND BE PREPARED TO PUT THE PLANS IN ACTION IF YOUR
AREA IS AFFECTED. PLEASE REPORT ANY STORM RELATED
INFORMATION TO YOUR LOCAL LAW ENFORCEMENT AGENCY FOR RELAY TO
THE NATIONAL WEATHER SERVICE.

NOTE: THE WEEKLY NOAA WEATHER RADIO ALERT TEST THAT IS NORMALLY
CONDUCTED ON WEDNESDAY HAS BEEN POSTPONED UNTIL THE NEXT CLEAR
WEATHER DAY.

FOR MORE INFORMATION...VISIT THE NEW ORLEANS/BATON ROUGE NATIONAL
WEATHER SERVICE FORECAST OFFICE WEB SITE AT WWW.SRH.NOAA.GOV/LIX (ALL
LOWER CASE LETTERS).