SWODY3
SPC AC 130728
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT WED APR 13 2011
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER TO
MID-MS VALLEY...CNTRL GULF COAST...TN VALLEY AND OH VALLEY...
...LOWER TO MID-MS VALLEY/CNTRL GULF COAST/TN VALLEY/OH VALLEY...
A STRONG NEGATIVELY-TILED UPPER-LEVEL LOW IS FORECAST TO MOVE FROM
THE CNTRL PLAINS EWD INTO THE OZARKS ON FRIDAY. THE EXIT REGION OF A
WELL-DEVELOPED 80 TO 100 KT MID-LEVEL JET IS FORECAST TO SPREAD
ACROSS THE CNTRL GULF COAST STATES DURING THE DAY CREATING STRONG
DEEP LAYER SHEAR PROFILES FAVORABLE FOR SEVERE STORMS. THE
GFS...ECMWF AND NAM BEGIN THE DAY 3 PERIOD WITH AN MCS LOCATED IN
THE MID-MS VALLEY DRIVING THIS FEATURE EWD INTO WRN KY AND WRN TN BY
MIDDAY. SOUTH ACROSS THE WARM SECTOR...THE MODELS DEVELOP MODERATE
INSTABILITY ACROSS MUCH OF THE CNTRL GULF COAST STATES AND INITIATE
NUMEROUS THUNDERSTORMS FROM MIDDLE TN SWWD INTO NCNTRL AL...MS AND
SE LA DURING THE AFTERNOON. THE DEVELOPMENT OF A SEVERE MCS SEEMS
PROBABLE ACROSS THE CNTRL AND SRN PARTS OF THE SLIGHT RISK AREA
FRIDAY AFTERNOON AND EVENING.
FORECAST SOUNDINGS IN CNTRL MS AND WRN AL AT 21Z ON FRIDAY SHOW
IMPRESSIVE WIND SHEAR PROFILES WITH 50 TO 60 KT OF 0-6 KM SHEAR AND
0-3 KM STORM RELATIVE HELICITIES AROUND 400 M2/S2. THIS ENVIRONMENT
SHOULD SUPPORT SUPERCELL DEVELOPMENT WITH A THREAT FOR STRONG
TORNADOES POSSIBLE. HOWEVER...THE MAGNITUDE OF THE TORNADO THREAT
WILL BE CONDITIONAL UPON STORM MODE. IF A SQUALL-LINE WERE TO
DEVELOP INSTEAD OF MORE DISCRETE CONVECTION....THEN WIND DAMAGE
COULD BE THE GREATER THREAT. THE UPPER-LEVEL SYSTEM IS QUITE
IMPRESSIVE WITH A WELL-DEVELOPED LOW-LEVEL JET IN PLACE ACROSS THE
ECNTRL STATES. THE GFS AND NAM SOLUTIONS FOCUS THE LOW-LEVEL JET
FURTHER NORTH IN TN AND KY BY LATE AFTERNOON WHILE THE ECMWF SHOWS A
STRONG COMPONENT OF THE JET IN THE TN VALLEY AND CNTRL GULF COAST
STATES. IF THE ECMWF SOLUTION IS CORRECT AND MOISTURE RETURN ENDS UP
BEING STRONGER THAN FORECAST...THEN A TORNADO OUTBREAK COULD OCCUR
IN PARTS OF WRN TO MIDDLE TN...MS AND AL FRIDAY AFTERNOON. AT THIS
POINT...THE POTENTIAL FOR AN OUTBREAK REMAINS CONDITIONAL AND
DIFFERENCES IN THE MODEL SOLUTIONS RAISE UNCERTAINTIES CONCERNING
THE EXACT SCENARIO.
FURTHER NORTH ACROSS THE OH VALLEY...SEVERE STORMS WILL ALSO BE
POSSIBLE FRIDAY AFTERNOON AS THE UPPER-LEVEL LOW APPROACHES FROM THE
WEST. IN SPITE OF WEAKER INSTABILITY...A STRONG WIND FIELD IS
FORECAST WITH COLD TEMPS ALOFT. THIS WOULD RESULT IN A POTENTIAL FOR
HAIL AND WIND DAMAGE WITH THE MORE ORGANIZED CONVECTIVE CLUSTERS. A
TORNADO THREAT WILL ALSO BE POSSIBLE IN THE OH VALLEY DUE TO THE
STRONG LOW-LEVEL SHEAR FORECAST BUT THIS POTENTIAL SHOULD BE
DEPENDENT UPON MOISTURE RETURN.
..BROYLES.. 04/13/2011
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