DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 280900
SWOD48
SPC AC 280859

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT MON OCT 28 2013

VALID 311200Z - 051200Z

...DISCUSSION...
A SEVERE RISK REMAINS APPARENT ESPECIALLY ON DAY 4/THURSDAY. THIS
WILL BE AS A CONSIDERABLE UPPER TROUGH AND ASSOCIATED
EASTWARD-ACCELERATING COLD FRONT SPREAD EASTWARD AND INTERCEPT A
SEASONALLY MOIST LOW-LEVEL AIRMASS FROM THE ARKLATEX/LOWER MS RIVER
VALLEY INTO THE TN/OH RIVER VALLEYS. WHILE EARLY-DAY CONVECTION IS
AN UNCERTAINTY FACTOR...CURRENT THINKING IS THAT THE MOST FAVORABLE
/OR CERTAIN/ COMBINATION OF MODEST INSTABILITY/STRONG VERTICAL SHEAR
WILL BE ACROSS PORTIONS OF THE ARKLAMISS/TN VALLEY...ALTHOUGH
MID-LEVEL LAPSE RATES WILL BE WEAKER WITH SOUTHERN EXTENT. GIVEN A
VERY MOIST LOW-LEVEL AIRMASS AND AMPLE LOW-LEVEL/DEEP-LAYER
SHEAR...DAMAGING WINDS AND SOME TORNADOES /POTENTIALLY A FEW STRONG/
WILL BE POSSIBLE.

FARTHER NORTH ON DAY 4/THURSDAY...ALTHOUGH THE EXACT DEGREE OF
DESTABILIZATION IS UNCERTAIN...A SEVERE /DAMAGING WIND AND PERHAPS
TORNADO/ RISK CANNOT BE DISCOUNTED FOR ADDITIONAL PORTIONS OF THE OH
VALLEY/NEARBY GREAT LAKES. THIS INCLUDES THE POSSIBILITY OF A
STRONGLY FORCED/LOW-TOPPED CONVECTIVE LINE IN ASSOCIATION WITH
ROBUST VERTICAL SHEAR/FORCING FOR ASCENT.

INTO DAY 5/FRIDAY...THE STRONGEST UPPER TROUGH-ASSOCIATED ASCENT
SHOULD SPREAD AWAY FROM THE RICHEST LOW-LEVEL MOISTURE. EVEN SO...A
MOIST AIRMASS/VERY STRONG SHEAR COULD ACCOUNT FOR SOME STRONGER
STORMS ACROSS PARTS OF THE SOUTHEAST STATES AND PERHAPS ADDITIONAL
PARTS OF THE EASTERN CONUS.

..GUYER.. 10/28/2013

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