SPC DAY-1 CONVECTIVE OUTLOOK

05 May 1999 - 16:29:41 UTC 
disclaimer  "for information regarding the availability and timeliness of 
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ZCZC MKCSWODY1 000
ACUS1 KMKC 051626
MKC AC 051626

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 051630Z - 061200Z

REF WW NUMBER 0213...VALID TIL 1900Z

THERE IS A HIGH RISK OF SVR TSTMS OVER NRN AND CENTRAL LA...SRN AND
EAST CENTRAL AR...PARTS OF WRN AND MIDDLE TN...NWRN AL...AND NRN
AND CENTRAL MS TO THE RIGHT OF A LINE FROM 45 ENE MKL 50 N HSV TCL
JAN ESF 40 W POE 30 NNW SHV 30 W PBF 50 ENE LIT 35 ESE JBR 45 ENE
MKL.

SURROUNDING THE HIGH RISK AREA...THERE IS A MDT RISK OF SVR TSTMS
OVER EXTREME ERN TX...SRN AND ERN AR...SERN MO...EXTREME SRN
IL...SWRN KY...WRN AND MIDDLE TN...NRN AND W CENTRAL AL...SRN
MS...AND SRN LA TO THE RIGHT OF A LINE FROM 20 NE MDH 20 SSE OWB 40
ESE BWG 30 NNW CHA 15 NE GAD CKL 10 SW LFT 30 NNE HOU GGG 30 WNW
LIT 30 NW P02 20 NE MDH.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM
20 ESE PSX 30 E CLL TYR 50 NNW FTW 50 E OKC JEF 10 W FSD FAR
25 ENE RHI 50 NE MKE 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... 50 NNW DAB 30 N PIE ...CONT...
10 S PSX CLL 40 WSW TYR 10 ESE FTW 15 SSW MWL 65 NW ABI TCC
10 NNW TAD PUB 35 WNW P28 15 SW EMP 40 NW OMA HON 65 ENE MOT.

...SEVERE THUNDERSTORM FORECAST DISCUSSION...
POTENTIAL FOR ACTIVE SEVERE WEATHER EPISODE IS EXPECTED THIS
AFTERNOON INTO TONIGHT AS STRONG SHORT WAVE TROUGH EVIDENT IN WATER
VAPOR IMAGERY ENTERING THE SRN PLAINS MOVES EWD ACROSS OK AND TX
TODAY THEN LIFTS NEWD TONIGHT TOWARD THE MID MS VALLEY. AT THE
SURFACE THE PRIMARY LOW OVER SERN SD IS FORECAST TO LIFT SLOWLY
NEWD INTO SWRN MN...AS A MOISTURE DISCONTINUITY/DRY LINE ARCING SWD
ACROSS ERN MO/SWRN AR/ERN TX REMAINS QUASI-STATIONARY TODAY IN
ADVANCE OF A COLD FRONT EXTENDING ACROSS EXTREME ERN KS/ERN OK W
CENTRAL TX. THE COLD FRONT IS EXPECTED TO SURGE EWD ACROSS THE
LOWER MO RIVER VALLEY AND SRN PLAINS LATER THIS AFTERNOON AND
TONIGHT IN ASSOCIATION WITH THE SRN PLAINS SHORT WAVE TROUGH. A
SECONDARY SURFACE LOW IS EXPECTED TO DEVELOP OVER ERN TX THIS
AFTERNOON AND MOVE NEWD INTO THE MID MS VALLEY BY THE END OF THE
PERIOD. FINALLY...SURFACE AND VISIBLE SATELLITE DATA SUGGEST E/W
ORIENTED SURFACE BOUNDARY EXTENDING ALONG THE LA/AR BORDER EWD INTO
NRN AL WHICH MAY PROVIDE AN ADDITIONAL FOCUS FOR CONVECTIVE
DEVELOPMENT.

...ERN TX INTO THE LOWER MS VALLEY/TN VALLEY...
AIR MASS FROM ERN TX INTO MS AND WRN TN HAS BECOME VERY MOIST WITH
SURFACE DEW POINTS IN THE LOW 70S...AND STEEP MID LEVEL LAPSE RATES
SPREADING EWD ACROSS THIS AREA ARE RESULTING IN VERY UNSTABLE
ENVIRONMENT WITH LIFTED INDEX OF -6 TO -11 AND MUCAPE OF 2000-3500
J/KG. VISIBLE IMAGERY SHOWS REGIONS OF MINIMAL CLOUDS FROM ERN TX
ACROSS NRN LA INTO MS WHERE STRONGER HEATING WILL OCCUR...WHICH
SHOULD CONTRIBUTE TO ADDITIONAL DESTABILIZATION THIS AFTERNOON.  

A CLUSTER OF STRONG/SEVERE THUNDERSTORMS MOVING ACROSS NRN MS THIS
MORNING IS EXPECTED TO PROGRESS EWD INTO AL EARLY THIS AFTERNOON...
WEAKENING AS IT MOVES INTO LESSOR INSTABILITY. REDEVELOPMENT OF
STORMS IS EXPECTED THIS AFTERNOON OVER PARTS OF ERN TX/WRN LA/SWRN
AR AS LOW LEVEL CONVERGENCE INCREASES IN ASSOCIATION WITH THE
DEVELOPING SURFACE LOW AND DYNAMIC FORCING ALOFT ASSOCIATED WITH
THE APPROACHING 80 KT MID LEVEL JET STREAK INCREASES THE LARGE
SCALE ASCENT. OTHER CELLS MAY DEVELOP EWD INTO PARTS OF NRN MS/NRN
AL AND TN AS CONVERGENCE AND WARM ADVECTION STRENGTHENS ALONG AND
NORTH OF THE E/W CONVECTIVE BOUNDARY IN RESPONSE TO THE
INTENSIFYING LOW LEVEL JET OVER THE LOWER MS VALLEY.  

THE STRONG INSTABILITY AND DRY AIR ALOFT FAVOR SEVERE STORM
DEVELOPMENT WITH LARGE HAIL AND DAMAGING WIND POTENTIAL. IN
ADDITION...MODERATE HELICITY OF 150-300 M2/S2...STRONG 0-6 KM SHEAR
OF 20-30 M/S AND FAVORABLE STORM-RELATIVE MID LEVEL WINDS INDICATE
THE THREAT FOR TORNADIC SUPERCELLS TO FORM...ESPECIALLY DURING THE
LATE AFTERNOON AND EVENING HOURS. LATER IN THE EVENING A LINE OF
STRONG/SEVERE THUNDERSTORMS IS EXPECTED TO DEVELOP ALONG/AHEAD OF
THE ADVANCING COLD FRONT WHICH SHOULD CONTINUE ACROSS THE LOWER MS
VALLEY/TN VALLEY DURING THE OVERNIGHT HOURS.

...ERN OK/EXTREME NERN TX/WRN AR...
COLD TROUGH ALOFT ACCOMPANYING SHORT WAVE TROUGH ACROSS THE SRN
PLAINS IS CREATING VERY STEEP LAPSE RATES ACROSS WRN/CENTRAL OK
WHICH WILL SPREAD EWD THIS AFTERNOON AND EVENING. THIS INSTABILITY
IS EVIDENT IN MID LEVEL CONVECTION MOVING INTO CENTRAL OK AT THIS
TIME. STRONG HEATING AHEAD OF THIS ACTIVITY WILL PERMIT
DESTABILIZATION WITH LIFTED INDEX NEAR -5 THIS AFTERNOON AND
EVENING. A FEW HAIL PRODUCING THUNDERSTORMS ARE POSSIBLE THROUGH
THE EVENING. 

...UPPER AND MIDDLE MS VALLEY...
LARGE SCALE ASCENT AND COLD AIR ALOFT ASSOCIATED WITH THE UPPER LOW
OVER SERN SD WILL AID CONTINUED DEVELOPMENT OF THUNDERSTORMS WITHIN
LOW LEVEL MOISTURE AXIS FROM MN INTO PARTS OF IL. DIURNAL HEATING
WILL RESULT IN DESTABILIZATION WITH LIFTED INDEX AROUND -4
EXPECTED. A FEW THUNDERSTORMS CAPABLE OF PRODUCING LARGE HAIL ARE
POSSIBLE DURING THE AFTERNOON AND EVENING.          

...A PUBLIC SEVERE WEATHER OUTLOOK WILL BE ISSUED BY 1730Z...
 
..WEISS.. 05/05/99

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