MESOSCALE DISCUSSION 2202
   NWS STORM PREDICTION CENTER NORMAN OK
   0749 PM CDT SUN SEP 25 2011
   
   AREAS AFFECTED...NWRN TN...WRN KY...CNTRL/SRN IND...FAR SWRN OH
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 260049Z - 260315Z
   
   A MARGINAL SVR THREAT WILL EXTEND NNEWD INTO THE OHIO VALLEY REGION
   DURING THE EVENING INTO THE OVERNIGHT HOURS...AND THE ISSUANCE OF A
   WW IS UNLIKELY.
   
   LATEST SFC ANALYSIS DEPICTS A WAVY FRONT EXTENDING FROM SWRN OH INTO
   CNTRL/SWRN KY TO A 1004-MB SUBSYNOPTIC LOW OVER NWRN TN AND
   EXTENDING FARTHER SWWD INTO ERN AR. STRONG SFC PRESSURE FALLS...ON
   THE ORDER OF 2-3 MB PER 2 HRS...LIE WITHIN A NNE-SSW-ELONGATED ZONE
   FROM CNTRL IND INTO WRN KY. THESE PRESSURE FALLS ARE IN RESPONSE TO
   ASCENT OFFERED BY AN APPROACHING MID-LEVEL IMPULSE PIVOTING AROUND
   THE SRN PERIPHERY OF THE LARGER CYCLONIC GYRE OVER THE MID-MS
   VALLEY. THIS ASCENT IS BEING AUGMENTED BY MASS CONVERGENCE AT THE
   EXIT REGION OF AN INTENSE SSWLY LOW-LEVEL JET /50 KT AT 1.5-KM-AGL
   PER HOPKINSVILLE KY VWP DATA/...ENHANCED BY UPPER-LEVEL DIVERGENCE
   WITHIN THE RIGHT-ENTRANCE REGION OF A JET MAX OVER NRN IND. AS THE
   SFC LOW DEVELOPS TOWARD THE REGION OF MAXIMUM PRESSURE FALLS...AND
   SFC WINDS ENE OF THE LOW CENTER VEER FROM ELY TO SLY/SSELY IN
   RESPONSE TO ISALLOBARIC FORCING...THE FRONT WILL RETREAT NWD THROUGH
   THE COURSE OF THE EVENING AND OVERNIGHT HOURS. THIS WILL ADVECT
   MODESTLY RICHER BOUNDARY-LAYER MOISTURE /SFC DEWPOINTS IN THE MIDDLE
   60S/ INTO THE OH VALLEY...POTENTIALLY RESULTING IN VERY WEAK
   DESTABILIZATION. REGARDLESS...WIDESPREAD STRATIFORM
   PRECIPITATION...ALONG WITH NOCTURNAL COOLING...WILL LARGELY SUPPRESS
   ANY APPRECIABLE IN SITU DESTABILIZATION CONTRIBUTED BY MOISTURE
   ADVECTION IN THE ABSENCE OF WEAKER MID-LEVEL LAPSE RATES.
   FURTHERMORE...THE BULK OF DEEP-LAYER FORCING FOR ASCENT AND
   CONVECTION WILL LIKELY BE CONFINED TO THE COOL SIDE OF THE
   AFOREMENTIONED FRONT OWING TO THE STATIONARY NATURE OF THE MID-LEVEL
   GYRE.
   
   GIVEN THESE FACTORS...AN UPTICK IN ELEVATED/FORCED CONVECTION WILL
   LIKELY PROGRESS NNEWD DURING THE NEXT SEVERAL HRS...POTENTIALLY
   REACHING AS FAR NORTH AS THE I-70 CORRIDOR BY 03Z PER THE LATEST RUN
   OF THE EXPERIMENTAL HRRR. STORM-SCALE ROTATION WILL BE POSSIBLE WITH
   THE MORE VIGOROUS UPDRAFTS...OWING TO LONG/CLOCKWISE-CURVED
   HODOGRAPHS PER AREA OBSERVED SOUNDINGS AND RUC FORECAST SOUNDINGS
   /0-3 KM SRH VALUES EXCEEDING 300 M2 S-2/. STORMS WILL LIKELY REMAIN
   ROOTED ABOVE THE STABLE BOUNDARY LAYER...OFFERING A VERY MINIMAL SVR
   THREAT. HOWEVER...SHOULD A SUSTAINED STORM MANAGE TO INTERACT WITH
   THE RETREATING FRONT AND BECOME ROOTED AT THE SFC...A BRIEF/WEAK
   TORNADO OR SVR WIND GUST CANNOT BE ENTIRELY RULED OUT. WHILE
   CONVECTIVE TRENDS WILL BE MONITORED...THE MARGINAL NATURE OF THE
   THREAT WILL LIKELY PRECLUDE THE ISSUANCE OF A WW.
   
   ..COHEN.. 09/26/2011
   
   
   ATTN...WFO...ILN...LMK...OHX...IND...PAH...MEG...
   
   LAT...LON   39988462 38978489 37568600 36248719 36378850 37728793
               39558692 40188583 39988462