Hail and Damaging Wind in Louisiana, April 11, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
200 PM CDT SUN APR 10 2005

...A SEVERE WEATHER EVENT REMAINS LIKELY MONDAY THROUGH MONDAY
NIGHT...

.SHORT TERM...THE MAIN WEATHER STORY OVER THE NEXT 36 HOURS WILL BE
THE POWERFUL SPRINGTIME STORM SYSTEM EXPECTED TO MOVE ACROSS THE
FORECAST AREA.  TONIGHT THOUGH SHOULD REMAIN DRY AS MOST OF THE
ACTIVITY STAYS OFF TO OUR WEST.  SOUTH TO SOUTHEAST WINDS SHOULD
INCREASE ACROSS THE LOWER MISSISSIPPI VALLEY TONIGHT IN RESPONSE TO
THE STORM SYSTEM MOVING ACROSS THE SOUTHERN PLAINS.  THIS WILL
RESULT IN RISING DEWPOINTS ACROSS OUR AREA TONIGHT AS GULF MOISTURE
IS USHERED INTO THE REGION.  THIS RAPID INCREASE IN MOISTURE ON THE
NOSE OF THE LOW-LEVEL JET MAY RESULT IN THE DEVELOPMENT OF SOME
STRATOCUMULI AFTER MIDNIGHT.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP TONIGHT TO OUR
SOUTHWEST...THEN GRADUALLY SPREAD NORTHEAST THROUGH THE OVERNIGHT
HOURS AS MORE DEVELOPMENT OCCURS JUST TO THE WEST OF OUR FORECAST
AREA.  THERE IS SOME QUESTION AS TO THE STRENGTH AND TIMING OF THIS
CONVECTION BY THE TIME IT REACHES OUR WESTERN COUNTIES/PARISHES.
REGARDLESS OF THIS...THESE SHOWERS/STORMS ARE EXPECTED TO PLACE SOME
BOUNDARIES IN OUR FORECAST AREA.  WITH THE INITIAL UNCERTAINTY OF
THIS AREA OF PRECIPITATION...I WILL LEAVE THE CURRENT RAIN CHANCES
IN CHANCE TERRITORY.  CONSIDERING THE DYNAMICAL SUPPORT
UPSTREAM...MENTIONING OF THE POSSIBILITY OF SEVERE STORMS SEEMS
PRUDENT FOR AREAS WEST OF THE MISSISSIPPI RIVER OVERNIGHT.

BY THE TIME MONDAY MORNING ROLLS AROUND...THE CENTER OF THE
UPPER-LEVEL LOW IS EXPECTED TO MIGRATE INTO WESTERN KANSAS.  AN
INITIAL LOBE OF VORTICITY...NOW OVER THE CENTRAL PLAINS...IS
EXPECTED TO EJECT INTO THE MID-MISSISSIPPI VALLEY.  THIS VORTICITY
LOBE WILL BE PUSHED CLOSE TO THE AREA BY THE NOSE OF A ROUGHLY 100
KNOT UPPER-LEVEL JET.  WHEN THIS OCCURS...THE SHORTWAVE TROUGH IS
EXPECTED TO BECOME NEGATIVELY TILTED...AND RESULT IN AN
INCREASINGLY DIFFLUENT FLOW THROUGH A DEEP LAYER OF THE UPPER
ATMOSPHERE.  THE INCREASED DIFFLUENCE WILL PROVIDE ADDITIONAL
SUPPORT FOR UPWARD VERTICAL MOTION AS A DRYLINE MOVES TOWARD THE
SABINE RIVER.

THE LOW-LEVEL FLOW ASSOCIATED WITH THIS STORM SYSTEM IS QUITE
IMPRESSIVE...WITH A SOUTHERLY FLOW UPWARDS TO 60 KNOTS EXPECTED AT
850 MB.  LOW-LEVEL THETA-E VALUES ARE EXPECTED TO INCREASE
THROUGHOUT THE DAY...APPROACHING 340K OVER PARTS OF OUR REGION BY
MONDAY NIGHT.  WITH STRONG 0 TO 3 KM MOISTURE CONVERGENCE...AND
PRECIPITABLE WATER VALUES HOVERING AROUND 2 INCHES THROUGH THE
DAY...HEAVY RAINFALL/POSSIBLE FLOODING THANKS TO CELL TRAINING WILL
BE AN ADDITIONAL CONCERN WITH THE THUNDERSTORM ACTIVITY.  FOR
NOW...ILL CONTINUE MENTIONING THIS IN THE HAZARDOUS WEATHER
OUTLOOK...BUT WILL HOLD OFF ISSUING ANY SORT OF FLOOD OR FLASH FLOOD
WATCH AT THIS TIME.

IT LOOKS LIKE THE DEWPOINT FIELDS ON SOME OF THE COMPUTER MODELS MAY
BE CONTAMINATED BY CONVECTION AND COULD BE UNDERCUTTING THIS
PARTICULAR FIELD.  OBSERVATIONALLY...DEWPOINTS IN THE GULF ARE
ALREADY AROUND 70 DEGREES...AND I SEE NO PROBLEM IN GETTING MIDDLE
TO UPPER 60 DEWPOINTS INTO OUR AREA BY MONDAY.  MORE THAN AMPLE
INSTABILITY...BUOYANCY...AND SHEAR ARE EXPECTED TO BE IN OUR NECK OF
THE WOODS THROUGH MONDAY NIGHT.  FOR WHAT THEYRE WORTH...
MODEL-DERIVED INSTABILITY...BUOYANCY...AND SHEAR PARAMETERS POINT
TOWARD A LIFTED INDEX AROUND -4 DEGREES... 0 TO 3 KM CAPE AROUND
1500 JOULES/KG...AND 0 TO 3 KM HELICITIES WELL OVER 150 M2/S2.

ALL THESE PARAMETERS POINT TOWARD THE POSSIBILITY OF TORNADOES...IN
ADDITION TO LARGE HAIL AND DAMAGING WINDS.  SUPERCELLS WILL BE
POSSIBLE...ESPECIALLY IF ANY CONVECTION DEVELOPS AHEAD OF THE SQUALL
LINE.

TIMING-WISE...WERE THINKING MOST OF THE ACTION FOR THE FORECAST
AREA WILL BEGIN SOMETIME BETWEEN 1000 AM AND 200 PM.  SHOWERS AND
THUNDERSTORMS...SOME LIKELY SEVERE...ARE EXPECTED TO CONTINUE PRETTY
MUCH OFF-AND-ON INTO MONDAY NIGHT UNTIL THE COLD FRONT SWINGS
THROUGH.

THIS MORNINGS RUN OF THE COMPUTER MODELS REMAIN REMARKABLY
CONSISTENT...BOTH WITHIN THEMSELVES AND BETWEEN EACH OTHER.  ALL
THINGS STILL APPEAR TO BE ON TARGET FOR A LARGE-SCALE SEVERE WEATHER
EVENT MONDAY.  CONSIDERING HOW THIS HAS EVOLVED OVER THE PAST COUPLE
OF DAYS...WE MUST URGE EVERYONE NOT TO TAKE THIS EVENT LIGHTLY.  WE
WILL ISSUE ANOTHER SPECIAL WEATHER STATEMENT LATE THIS AFTERNOON IN
ADDITION TO THE REGULARLY-SCHEDULED HAZARDOUS WEATHER OUTLOOK.

A BIG THANK YOU GOES OUT TO THE CREW AT THE STORM PREDICTION CENTER
FOR THEIR COLLABORATION TODAY.  /#10/

.LONG TERM...AFTER THE SIGNIFICANT SEVERE OUTBREAK ENDS LATE TUESDAY
NIGHT (WITH THE SYSTEM MOVING OFF TO THE NORTHEAST)...CLOUDS ARE
EXPECTED TO LINGER OVER THE AREA AS THE UPPER LOW LINGERS OVER THE
MIDDLE MISSISSIPPI RIVER VALLEY. SPOTTY SHOWERS WILL BE POSSIBLE ON
WEDNESDAY AND THURSDAY ACROSS THE NORTH AS THE UPPER LOW BEGINS TO
DIVE SOUTHEASTWARD TOWARD GEORGIA. SINCE THE CORE OF THE UPPER LOW
IS EXPECTED TO REMAIN WELL EAST OF THE AREA...THINKING THAT THE
BETTER LAPSE RATES...AND THUS THE CHANCES OF ELEVATED
THUNDERSTORMS...WILL ALSO REMAIN EAST OF THE AREA.

ON FRIDAY AND SATURDAY...RIDGING ( IN BOTH THE LOW AND MID LEVELS)
WILL BUILD INTO THE AREA FROM THE WEST. THIS SHOULD ALLOW FOR SOME
CLEARING OF THE SKIES AS DRIER AIR WORKS ITS WAY INTO THE REGION. A
FEW THUNDERSTORMS MAY BE POSSIBLE SUNDAY NIGHT AND MONDAY AS ANOTHER
SYSTEM APPROACHES THE REGION FROM THE WEST. HOWEVER...THE RUN TO RUN
CONSISTENCY HAS NOT BEEN VERY GOOD WITH THIS SYSTEM AND SUCCESSIVE
RUNS HAVE CONTINUED TO DELAY ITS ARRIVAL.

&&

.LONG TERM...AFTER THE SIGNIFICANT SEVERE OUTBREAK ENDS LATE TUESDAY
NIGHT (WITH THE SYSTEM MOVING OFF TO THE NORTHEAST)...CLOUDS ARE
EXPECTED TO LINGER OVER THE AREA AS THE UPPER LOW LINGERS OVER THE
MIDDLE MISSISSIPPI RIVER VALLEY. SPOTTY SHOWERS WILL BE POSSIBLE ON
WEDNESDAY AND THURSDAY ACROSS THE NORTH AS THE UPPER LOW BEGINS TO
DIVE SOUTHEASTWARD TOWARD GEORGIA. SINCE THE CORE OF THE UPPER LOW
IS EXPECTED TO REMAIN WELL EAST OF THE AREA...THINKING THAT THE
BETTER LAPSE RATES...AND THUS THE CHANCES OF ELEVATED
THUNDERSTORMS...WILL ALSO REMAIN EAST OF THE AREA.

ON FRIDAY AND SATURDAY...RIDGING (IN BOTH THE LOW AND MID LEVELS)
WILL BUILD INTO THE AREA FROM THE WEST. THIS SHOULD ALLOW FOR SOME
CLEARING OF THE SKIES AS DRIER AIR WORKS ITS WAY INTO THE REGION. A
FEW THUNDERSTORMS MAY BE POSSIBLE SUNDAY NIGHT AND MONDAY AS ANOTHER
SYSTEM APPROACHES THE REGION FROM THE WEST. HOWEVER...THE RUN TO RUN
CONSISTENCY HAS NOT BEEN VERY GOOD WITH THIS SYSTEM AND SUCCESSIVE
RUNS HAVE CONTINUED TO DELAY ITS ARRIVAL.

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       63  78  58  75 /  10  80  80  20
MERIDIAN      60  81  58  78 /  10  70  90  30

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

BUTTS/HENRY

HAZARDOUS WEATHER OUTLOOK...CORRECTED TIMES
NATIONAL WEATHER SERVICE JACKSON MS
722 PM CDT SUN APR 10 2005

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
120022-
ADAMS-ASHLEY-ATTALA-BOLIVAR-CARROLL-CATAHOULA-CHICOT-CHOCTAW-
CLAIBORNE-CLARKE-CLAY-CONCORDIA-COPIAH-COVINGTON-EAST CARROLL-
FORREST-FRANKLIN LA-FRANKLIN MS-GRENADA-HINDS-HOLMES-HUMPHREYS-
ISSAQUENA-JASPER-JEFFERSON-JEFFERSON DAVIS-JONES-KEMPER-LAMAR-
LAUDERDALE-LAWRENCE-LEAKE-LEFLORE-LINCOLN-LOWNDES-MADISON LA-
MADISON MS-MARION-MONTGOMERY-MOREHOUSE-NESHOBA-NEWTON-NOXUBEE-
OKTIBBEHA-RANKIN-RICHLAND-SCOTT-SHARKEY-SIMPSON-SMITH-SUNFLOWER-
TENSAS-WARREN-WASHINGTON-WEBSTER-WEST CARROLL-WINSTON-YAZOO-
722 PM CDT SUN APR 10 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...
NORTHEAST LOUISIANA...AND EXTREME SOUTHEAST ARKANSAS

.DAY ONE...TONIGHT AND MONDAY...

...THUNDERSTORMS...
ISOLATED SEVERE THUNDERSTORMS WILL BE POSSIBLE BETWEEN MIDNIGHT
AND 600 AM WEST OF A JONESVILLE LOUISIANA TO LAKE VILLAGE
ARKANSAS LINE.	THE MAIN SEVERE WEATHER RISKS WILL BE LARGE HAIL
AND DAMAGING WINDS...ALTHOUGH ISOLATED TORNADOES CANNOT BE RULED
OUT.

NUMEROUS SEVERE THUNDERSTORMS WILL BE POSSIBLE MONDAY AND MONDAY
EVENING GENERALLY ALONG AND WEST OF INTERSTATE 55.  THIS AREA
INCLUDES LAKE VILLAGE AND CROSSETT
ARKANSAS...TALLULAH...WINNSBORO...AND VIDALIA LOUISIANA...AND
NATCHEZ...GREENVILLE...AND JACKSON.

EAST OF INTERSTATE 55...SCATTERED SEVERE THUNDERSTORMS ARE
EXPECTED.  THIS AREA INCLUDES THE CITIES OF
COLUMBUS...PHILADELPHIA...MERIDIAN...AND HATTIESBURG.

TORNADOES...HAIL GREATER THAN THREE QUARTERS OF AN INCH...AND
DAMAGING WINDS IN EXCESS OF 60 MILES AN HOUR WILL BE POSSIBLE.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP TONIGHT ACROSS
THE ARKLATEX...THEN BEGIN TO MOVE EAST.  SOME OF THESE STORMS MAY
BE SEVERE AS THEY APPROACH AREAS WEST OF A JONESBORO LOUISIANA TO
LAKE VILLAGE ARKANSAS LINE PRIOR TO SUNRISE.

A POTENT SPRINGTIME STORM WILL MOVE INTO THE LOWER MISSISSIPPI
VALLEY MONDAY.	MOISTURE...LIFT...AND INSTABILITY IS EXPECTED TO
INCREASE AS LOW PRESSURE DEVELOPS TO OUR WEST.	WITH POWERFUL JET
STREAM DYNAMICS POISED TO MOVE INTO THE REGION...AND STRONG WIND
SHEAR (OR THE CHANG IN WIND DIRECTION AND/OR SPEED WITH HEIGHT)
IN PLACE...MANY OF THESE STORMS WILL LIKELY BECOME SEVERE.
TOGETHER...THESE FEATURES RESEMBLE A CLASSIC SEVERE WEATHER SETUP
FOR THE LOWER MISSISSIPPI VALLEY. A GREATER RISK FOR SIGNIFICANT
SEVERE WEATHER...INCLUDING ISOLATED STRONG TORNADOES...SEEMS TO
BE POINTED AT THE AREA ALONG AND WEST OF THE MISSISSIPPI
RIVER...WHERE THE STRONGEST COMBINATION OF SEVERE WEATHER
PARAMETERS WILL EXIST.

...FLOODING...
HEAVY RAINFALL WILL BE POSSIBLE ACROSS EXTREME SOUTHEAST
ARKANSAS...EAST LOUISIANA...AND MUCH OF MISSISSIPPI MONDAY AND
MONDAY NIGHT.

A POWERFUL SPRINGTIME STORM SYSTEM WILL AFFECT THE LOWER
MISSISSIPPI VALLEY MONDAY AND MONDAY NIGHT.  WITH COPIOUS AMOUNTS
OF MOISTURE IN PLACE...HEAVY RAINFALL WILL BE POSSIBLE WITH ANY
OF THE THUNDERSTORMS.

BETWEEN TWO AND FOUR INCHES OF RAIN MAY BE SEEN OVER PARTS OF THE
REGION.  RAINFALL AMOUNTS SUCH AS THESE MAY RESULT IN THE PONDING
OF WATER ON AREA ROADWAYS...AND LOCALIZED FLOODING OF LOW-LYING
AND OTHER FLOOD-PRONE AREAS.  THIS AMOUNT OF RAIN WILL ONLY
EXASPERATE ANY ONGOING RIVER FLOODING.

.DAYS TWO THROUGH SEVEN...MONDAY NIGHT THROUGH SUNDAY...

...DAYS TWO AND THREE...MONDAY NIGHT THROUGH WEDNESDAY...THE
POTENTIAL FOR SEVERE WEATHER WILL CONTINUE INTO MONDAY NIGHT FOR
MOST OF THE OUTLOOK AREA...ESPECIALLY IN THE AREA EAST OF THE
MISSISSIPPI RIVER. AT THIS TIME...IT APPEARS THE GREATEST POTENTIAL
FOR SEVERE WEATHER WILL BE IN THE EARLY EVENING WHEN INSTABILITY
SHOULD BE GREATER.

LATER IN THE NIGHT...THE COLD FRONT WILL SWEEP THROUGH	AND BRING
AN END TO THUNDERSTORM ACTIVITY...PROBABLY SHORTLY AFTER
MIDNIGHT.

...DAYS FOUR THROUGH SEVEN...WEDNESDAY NIGHT THROUGH SUNDAY...
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTER GROUPS...HAM RADIO
OPERATORS...AND EMERGENCY MANAGEMENT PERSONNEL...IN SUPPORT OF
SEVERE WEATHER OPERATIONS...WILL LIKELY BE NEEDED MONDAY AND
MONDAY NIGHT.  OTHERWISE...ACTIVATION IS NOT EXPECTED THROUGH THE
EVENING OF SUNDAY APRIL 17.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.