05 May 1999 - 12:54:08 UTC 
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ZCZC MKCSWODY1 000
ACUS1 KMKC 051254
MKC AC 051254

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 051300Z - 061200Z

REF WW NUMBER 0213...VALID TIL 1900Z

THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING FOR
EXTREME EASTERN ARKANSAS...NORTHERN MISSISSIPPI...SOUTHWEST
TENNESSEE...AND NORTHWEST ALABAMA TO THE RIGHT OF A LINE FROM
45 ENE MKL 50 N HSV 25 NE HSV 45 SW HSV 30 SW CBM 45 SE GLH
40 NE MLU 35 SSE PBF 60 E LIT 35 ESE JBR 45 ENE MKL.

SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS FOR
NORTHEAST LOUISIANA...EASTERN ARKANSAS...SOUTHEAST MISSOURI...
EXTREME SOUTH ILLINOIS...WESTERN KENTUCKY...NORTHWEST AND MIDDLE
TENNESSEE...PARTS OF WEST CENTRAL AND NORTHEAST ALABAMA...AND
CENTRAL MISSISSIPPI TO THE RIGHT OF A LINE FROM 20 NE MDH 20 SSE
OWB 40 ESE BWG 30 NNW CHA 15 NE GAD 25 SSW TCL 40 NNW LUL 15 N HEZ
30 WNW MLU 15 ENE LIT 30 NW P02 20 NE MDH.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM
20 NW BVE 25 NE LCH SHV 30 S HRO 10 E COU 30 ENE FOD 15 WSW STC
45 WSW DLH 25 ENE RHI 50 NE MKE 25 WSW IND 25 SSW LEX 10 ENE TYS
ATL 45 NE DHN 30 SSW CEW.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 10 NW ROC 15 W CXY
25 WNW NHK 35 S WAL ...CONT... 40 SW MYR 45 N SAV 35 NNW AYS
40 WNW CTY ...CONT... 25 SSW BPT 30 NW LFK 40 NNW GGG 45 ENE DAL
15 SSW MWL 65 NW ABI TCC 10 NNW TAD 25 SW LIC 35 WNW P28 15 SW EMP
40 NW OMA HON 65 ENE MOT.

...SYNOPSIS...

A DEEP OCCLUDED LOW OVER WESTERN MINNESOTA IS FORECAST TO MOVE VERY
LITTLE OVER THE NEXT 24 HOURS. A SHORT WAVE TROUGH/UPPER SPEED
MAXIMUM SHOULD ROTATE BENEATH OF THE UPPER LOW AND MOVE ACROSS
OKLAHOMA/NORTH TEXAS DURING THE DAY...EVENTUALLY CROSSING ARKANSAS
AND MISSOURI TONIGHT. THIS WILL LIKELY INDUCE A WEAK WAVE OF LOW
PRESSURE ALONG SURFACE FRONT IN THE VICINITY OF ARKANSAS THIS
AFTERNOON AND EVENING. EAST OF THE LOW PRESSURE WAVE ACROSS THE
MID-SOUTH...A WEST-EAST WARM FRONT IS FORECAST TO BECOME BETTER
DEFINED DURING THE AFTERNOON AND EVENING HOURS AS IT LIFTS SLOWLY
NORTH INTO THE TENNESSEE VALLEY.

...SEVERE THUNDERSTORM FORECAST DISCUSSION...

...LOWER MISSISSIPPI RIVER VALLEY...

---THE POTENTIAL FOR NUMEROUS SEVERE THUNDERSTORMS INCLUDING A FEW
STRONG TORNADIC SUPERCELLS IS RELATIVELY HIGH OVER PORTIONS OF THE
AREA THIS AFTERNOON AND EVENING---

LATEST SURFACE DATA SHOWS LOW LEVEL MOIST AXIS FROM SOUTHEAST TEXAS
AND LOUISIANA INTO THE MEMPHIS TN AREA...WITH DEWPOINTS MOSTLY IN
THE LOWER 70S F. PER 12Z SOUNDINGS...AIRMASS IS ALREADY VERY
UNSTABLE WITH MUCAPE OF 2000-3500 J/KG...AND ENVIRONMENT IS
ESSENTIAL UNDISTURBED BY SPARSE COVERAGE OF EXISTING CONVECTION. 
MID LEVEL LAPSE RATES ARE QUITE FAVORABLE FOR SEVERE CONVECTION...
WITH 700-500 MB VALUES RANGING FROM 7.3 C/KM AT BMX TO 9 C/KM
UPSTREAM AT CRP.  

MID LEVEL FLOW IS ALREADY QUITE STRONG FROM TEXAS INTO THE MIDDLE
MISSISSIPPI RIVER VALLEY...WITH 500 MB OBSERVED WINDS OF 70 KNOTS
AT SHV AND 85 KNOTS AT SGF. ASSOCIATED DEEP LAYER SHEAR VALUES ARE
SUPPORTIVE OF SUPERCELLS...WITH 12Z OBSERVED BRN SHEAR VALUES OF
70-100 M2/S2.    

STORMS NOW IN SOUTHERN ARKANSAS APPEAR TO BE DEVELOPING IN RESPONSE
TO ENHANCED ISENTROPIC ASCENT DOWNSTREAM FROM SOUTHERN BRANCH
IMPULSE NOW OVER CENTRAL TEXAS. ADDITIONAL DEVELOPMENT IS EXPECTED
AS UPPER SHORT WAVE TROUGH OVER WEST TEXAS APPROACHES THE AREA LATE
THIS AFTERNOON AND EVENING. INCREASING UPPER DIVERGENCE/UVVS IN
RIGHT ENTRANCE REGION OF UPPER JET STREAK OVER THE MIDDLE
MISSISSIPPI RIVER VALLEY WILL ENHANCE CONVECTIVE POTENTIAL. AS
DIURNAL HEATING DESTABILIZES BOUNDARY LAYER...THUNDERSTORMS ARE
EXPECTED TO INCREASE RAPIDLY IN COVERAGE/INTENSITY THIS AFTERNOON
AND SPREAD EAST ALONG WARM FRONT BY THE EVENING HOURS.  

DEGREE OF INSTABILITY AND VERTICAL WIND SHEAR SUGGEST THAT
SIGNIFICANT SUPERCELLS/TORNADOES ARE POSSIBLE...ESPECIALLY NEAR
WEST-EAST SURFACE BOUNDARY. ACTIVITY WILL BECOME WIDESPREAD DURING
THE LATE AFTERNOON/EVENING...POSSIBLY EVOLVING INTO A SQUALL LINE
ALONG ADVANCING COLD FRONT WITH DAMAGING WINDS BECOMING AN
INCREASING THREAT AS FAR SOUTH AS THE CENTRAL GULF COAST LATE IN
THE PERIOD.   

...UPPER MISSISSIPPI RIVER VALLEY...

MODERATE UVVS ARE LIKELY DUE TO COMBINATION OF BROAD CYCLONIC LOW
LEVEL FLOW AND LEFT EXIT REGION OF 80 KNOT MID LEVEL JET. 
RELATIVELY COOL MID LEVEL TEMPERATURES AROUND -16 C WILL LEAD TO
MODERATE LOW/MID LEVEL LAPSE RATES OF 6.5 TO 7 C/KM. ISOLATED
THUNDERSTORMS ARE ALREADY OCCURRING...BUT COVERAGE SHOULD INCREASE
BY THE EARLY AFTERNOON AS DIURNAL HEATING DESTABILIZES AIRMASS. 
MLCAPE OF 500-1000 J/KG SHOULD BE SUFFICIENT FOR SEVERE
THUNDERSTORMS WITH HAIL...ESPECIALLY GIVEN 12Z OBSERVED WET BULB
ZERO HEIGHT OF ABOUT 7000 FEET AGL AT MPX.  

...GENERAL THUNDERSTORM FORECAST DISCUSSION...

...OKLAHOMA AREA...

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED WITH DIURNAL
HEATING ON CYCLONIC SIDE OF MIDDLE/UPPER JET THIS AFTERNOON AND
EARLY EVENING. VERY STEEP LOW/MID LEVEL LAPSE RATES IN EXCESS OF
8 C/KM ARE EXPECTED BENEATH UPPER COLD POOL AS 500 MB TEMPERATURES
OF -20 TO -24 C SPREAD EAST FROM THE TEXAS PANHANDLE INTO OKLAHOMA.
MLCAPE OF 500-1000 J/KG AND WET BULB ZERO HEIGHTS OF ABOUT 5000
FEET AGL SHOULD BE SUFFICIENT FOR ISOLATED HAIL PRODUCTION. 
 
..CRAVEN.. 05/05/99

NNNN


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