SWODY1
SPC AC 170558
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1158 PM CST SAT FEB 16 2008
VALID 171200Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN
LA...MS...AL..GA...SC...NC AND TN...
..TN VALLEY...
A NEGATIVELY-TILTED UPPER-LEVEL TROUGH IS FORECAST TO LIFT NNEWD
ACROSS THE MS VALLEY AS A PRE-FRONTAL TROUGH ADVANCES QUICKLY EWD
ACROSS THE LOWER MS VALLEY INTO THE TN VALLEY TODAY. AT 12Z...A
SQUALL-LINE NEAR THE SRN END OF THE MS VALLEY AHEAD OF THE
PRE-FRONTAL TROUGH WILL MOVE EWD ACROSS MS...AL INTO GA BY THIS
EVENING. ANOTHER BAND OF CONVECTION SHOULD DEVELOP ALONG THE
PRE-FRONTAL TROUGH ACROSS MIDDLE TN AND NRN AL LATE THIS AFTERNOON
INTO EARLY THIS EVENING.
CONCERNING THE SEVERE THREAT...A 100 KT MID-LEVEL JET OVER THE MID
MS VALLEY WILL MOVE NEWD ACROSS THE TN AND OH VALLEYS CREATING
STRONG VERTICAL SHEAR PROFILES ACROSS THE REGION. LIFT WILL BE
ENHANCED FROM THE RIGHT REAR QUADRANT OF THE JET ACROSS THE TN
VALLEY AND THIS ALONG WITH THE STRONG SHEAR WILL SUPPORT A SEVERE
THREAT WITH THE SQUALL-LINE. FORECAST SOUNDINGS AHEAD OF THE
SQUALL-LINE THIS AFTERNOON SHOW IMPRESSIVE LOW-LEVEL SHEAR PROFILES
WITH ABOUT 50 KT AT 850 MB AND RESULTANT 0-1 KM SHEAR VALUES AROUND
30 KT. THIS SHOULD BE FAVORABLE FOR TORNADOES WITH SUPERCELLS AHEAD
OF THE LINE AND PERSISTENT ROTATING STORMS EMBEDDED IN THE LINE. IF
SUPERCELLS INITIATE EAST OF THE SQUALL-LINE...THEN AN ISOLATED
STRONG TORNADO OR TWO MAY OCCUR ACROSS SRN AND CNTRL AL. A POTENTIAL
FOR WIND DAMAGE AND HAIL WILL LIKELY EXIST AT THE BEGINNING OF THE
PERIOD AND PERSIST THROUGH THIS EVENING AS THE SQUALL-LINE ADVANCES
EWD ACROSS THE REGION. THE SEVERE THREAT SHOULD BE GREATEST ACROSS
SRN AND CNTRL AL IN THE EARLY TO MID AFTERNOON WHEN INSTABILITY WILL
BE MAXIMIZED WITH THE THREAT CONTINUING EWD INTO WRN GA BY EARLY
THIS EVENING. CONVECTIVE DEVELOPMENT MAY ALSO OCCUR LATE THIS
AFTERNOON BEHIND THE SQUALL-LINE FROM MIDDLE TN SWD ACROSS NRN AL.
ALTHOUGH THIS CONVECTION SHOULD REMAIN SHORT-TOPPED...THE STORMS
WILL HAVE ACCESS STEEPER MID-LEVEL LAPSE RATES. AS A RESULT...LARGE
HAIL MAY OCCUR ACROSS THE NWRN PART OF THE SLIGHT RISK AREA. HAIL
WILL ALSO BE POSSIBLE NEWD ACROSS ERN KY INTO WV UNDER THE AXIS OF
THE MID-LEVEL JET WHERE VERTICAL SHEAR WILL BE VERY STRONG AND TEMPS
WILL ALSO BE COLD ALOFT.
..CAROLINAS...
A WARM FRONT IS FORECAST TO MOVE NWD ACROSS THE REGION TODAY AND SFC
DEWPOINTS SHOULD RISE INTO THE 60S F IN THE ERN CAROLINAS BY 06Z
TONIGHT. INCREASING LARGE-SCALE ASCENT ASSOCIATED WITH THE
APPROACHING UPPER-LEVEL TROUGH AND STRONG LIFT ALONG THE AXIS OF THE
LOW-LEVEL JET WILL LIKELY RESULT IN SCATTERED THUNDERSTORM
DEVELOPMENT AFTER MIDNIGHT. FORECAST SOUNDINGS ACROSS ERN NC AT 09Z
SUGGEST 0-6 KM SHEAR VALUES WILL RANGE FROM 50 TO 60 KT AND THIS
SHOULD BE SUFFICIENT FOR ORGANIZED SEVERE STORMS. ISOLATED WIND
DAMAGE AND HAIL WOULD LIKELY BE THE PRIMARY THREATS. THE EXTENT OF
THE SEVERE THREAT SHOULD DEPEND UPON HOW MUCH INSTABILITY IS
REALIZED ACROSS THE REGION BY LATE IN THE PERIOD.
.BROYLES.. 02/17/2008
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