New SPC mesoscale update:
"A REGIONAL OUTBREAK OF SEVERE THUNDERSTORMS WILL CONTINUE TONIGHT
ACROSS PARTS OF THE MID MISSISSIPPI, OHIO AND TENNESSEE VALLEYS.
THIS WILL INCLUDE INTENSE SUPERCELLS WITH STRONG, POTENTIALLY
LONG-TRACK TORNADOES AND VERY LARGE HAIL. THE THREAT FOR DAMAGING
WINDS IN EXCESS OF 75 MPH WILL INCREASE THIS EVENING AS STORMS GROW
INTO LARGER CLUSTERS.
..01Z UPDATE
SEASONALLY DEEP CYCLONE IS SHIFTING EAST ACROSS THE UPPER MS VALLEY
TOWARD THE UPPER GREAT LAKES REGION. EARLY-EVENING SATELLITE IMAGERY
SUPPORTS THIS WITH THE CENTER OF THE UPPER LOW CURRENTLY OVER
NORTHERN MN. MULTIPLE SHORT-WAVE TROUGHS ARE ROTATING INTO/THROUGH
THE BASE OF THE TROUGH, BUT THE PRIMARY ZONE OF NOTEWORTHY ASCENT IS
CURRENTLY AIDING AN ELONGATED CORRIDOR OF DEEP CONVECTION FROM
CENTRAL INDIANA, SOUTHWEST ACROSS NORTHERN ARKANSAS INTO CENTRAL TX,
WHERE ONLY THE SOUTHERN INFLUENCE OF THIS UPPER TROUGH IS EVIDENT.
MULTIPLE LONG-LIVED SUPERCELLS HAVE EVOLVED ALONG THIS CORRIDOR,
ESPECIALLY FROM SOUTHERN INDIANA INTO NORTHEAST ARKANSAS. THIS ZONE
IS STRONGLY SHEARED, STRONGLY BUOYANT, AND ADEQUATELY FORCED FOR THE
CONTINUATION OF SEVERE SUPERCELLS. ENVIRONMENTAL CONDITIONS REMAIN
FAVORABLE FOR INTENSE UPDRAFTS, ALONG WITH THE POTENTIAL FOR
LONG-TRACK TORNADOES. VERY LARGE HAIL AND SEVERE WINDS ARE ALSO
LIKELY WITH THIS ACTIVITY. THROUGH LATE EVENING, THE PRIMARY
CORRIDOR FOR THE MOST CONCENTRATED SEVERE WILL EXTEND FROM NORTHEAST
ARKANSAS INTO CENTRAL KENTUCKY. LATER TONIGHT, SOME POTENTIAL FOR
UPSCALE GROWTH MAY YIELD A FORWARD PROPAGATING MCS. THIS ACTIVITY
WILL MOVE TOWARD THE CENTRAL/SOUTHERN APPALACHIANS WITH AN ATTENDANT
SEVERE RISK, INCLUDING ALL SEVERE HAZARDS."