SPC AC 300600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1200 AM CST THU NOV 30 2006
VALID 301200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS AND TN
VALLEYS INTO THE SERN U.S. AND A SMALL PART OF THE OH VALLEY...
...SYNOPSIS...
STRONG SHORTWAVE TROUGH OVER NM WILL AMPLIFY ESEWD THROUGH THE SRN
PLAINS THURSDAY BEFORE EJECTING NEWD INTO THE LOWER-MID MS VALLEY
AND WRN TN VALLEY THURSDAY EVENING...REACHING THE OH VALLEY LATE
THURSDAY NIGHT. ARCTIC FRONT SHOULD EXTEND FROM THE GREAT LAKES SWWD
INTO AR AND SRN TX BY 12Z THURSDAY. CYCLOGENESIS WILL COMMENCE ALONG
LOWER MS VALLEY PORTION OF FRONT THURSDAY AFTERNOON AS ASCENT WITHIN
DIVERGENT EXIT REGION OF CYCLONIC UPPER JET BEGINS TO OVERTAKE WARM
SECTOR. THE LOW WILL SUBSEQUENTLY DEEPEN AND LIFT NEWD INTO THE OH
VALLEY OVERNIGHT. THIS SHOULD RESULT IN SRN PORTION OF THE COLD
FRONT ACCELERATING EWD THROUGH THE TN VALLEY AND SERN U.S. THURSDAY
EVENING AND NIGHT.
...SERN TX THROUGH THE LOWER MS AND TN VALLEYS AND SERN STATES...
MODIFIED CP AIR WITH BOUNDARY LAYER DEWPOINTS MOSTLY IN THE LOW TO
MID 60S WILL EXIST IN PRE-FRONTAL WARM SECTOR OVER THE LOWER MS
VALLEY AND PORTIONS OF THE SERN STATES WITH NEAR 60 FARTHER N INTO
THE TN AND OH VALLEYS. THIS MOISTURE WILL EXIST BELOW WEAK MID LEVEL
LAPSE RATES WITH 5.5 C/KM EXPECTED IN THE 850-500 MB LAYER. THE WEAK
LAPSE RATES AND LIMITED BOUNDARY LAYER HEATING SHOULD RESULT IN WEAK
INSTABILITY WITH MLCAPE GENERALLY AOB 500 J/KG.
BY 12Z THURSDAY STORMS WILL BE ONGOING MAINLY ON COLD SIDE OF ARCTIC
FRONT FROM SERN TX INTO THE LOWER-MID MS VALLEY. ANY SEVERE THREAT
WITH THIS ACTIVITY WILL BE MINIMAL DUE TO ELEVATED NATURE OF THE
STORMS AND WEAK INSTABILITY. THREAT FOR SEVERE STORMS MAY INCREASE
FARTHER EAST THURSDAY AFTERNOON INTO THURSDAY EVENING OVER PARTS OF
THE LOWER MS VALLEY INTO THE TN VALLEY. DEEP LAYER FORCING ALONG
FRONT WILL INCREASE IN THIS REGION AS THE SURFACE LOW DEEPENS AND
LOW LEVEL JET STRENGTHENS. THIS MAY CONTRIBUTE TO A LINE OF LOW
TOPPED CONVECTION...POSSIBLY WITH LITTLE OR NO
LIGHTNING...ESPECIALLY FROM ERN AR...MS INTO WRN TN AND KY. WITH THE
LOW LEVEL JET FORECAST TO STRENGTHEN TO 60+ KT...POTENTIAL WILL
EXIST FOR MAINLY ISOLATED DAMAGING WIND ALONG THE LINE.
SOME STORMS MAY BECOME UNDERCUT BY THE COLD AIR ACCOMPANYING EWD
MOVING FRONT. HOWEVER...FRONT WILL BECOME ORIENTED MORE N-S DURING
THE AFTERNOON S OF THE SURFACE LOW...AND THIS PORTION OF BOUNDARY
MAY TREND TOWARD A KATAFRONT. THIS MAY SUPPORT A FEW SURFACE BASED
STORMS BEING MAINTAINED ALONG THE SURFACE FRONT AS IT MOVES EWD
THROUGH THE TN VALLEY AND SRN PORTIONS OF THE OH VALLEY.
STRENGTHENING LOW-LEVEL AND CLOUD LAYER SHEAR PROFILES WOULD ALSO
SUPPORT A THREAT OF SUPERCELL STRUCTURES EMBEDDED WITHIN THE LINE.
ANY TORNADO THREAT WILL BE MAINLY LIMITED TO STORMS THAT CAN DEVELOP
IN WARM SECTOR E OF ADVANCING COLD FRONT. HOWEVER...IT MAY BE
DIFFICULT TO MAINTAIN DISCRETE UPRIGHT CONVECTION AWAY FROM THE
FRONT IN SUCH A STRONGLY SHEARED ENVIRONMENT...AND THIS MAY SERVE AS
A LIMITING FACTOR FOR A MORE ROBUST TORNADO THREAT.
..DIAL/GRAMS.. 11/30/2006
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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