MESO: Mesoscale Discussion 1680

ACUS11 KWNS 212225
SWOMCD
SPC MCD 212225
TNZ000-KYZ000-MSZ000-ARZ000-220030-

MESOSCALE DISCUSSION 1680
NWS STORM PREDICTION CENTER NORMAN OK
0525 PM CDT THU JUL 21 2011

AREAS AFFECTED...WRN TN...SWRN KY...FAR NRN MS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 212225Z - 220030Z

THE BROKEN SQUALL LINE OVER PORTIONS OF TN/KY COULD POSE A THREAT
FOR STRONG WIND GUSTS INTO THIS EVENING AS IT APPROACHES THE MS
RIVER. WHILE CONVECTIVE TRENDS WILL BE MONITORED...THE OVERALL LACK
OF CONVECTIVE ORGANIZATION WILL LIKELY PRECLUDE THE NEED FOR A WW.

A BROKEN CONVECTIVE LINE AND TRAILING STRATIFORM REGION ARE MOVING
WWD ACROSS PORTIONS OF THE TN VALLEY AND LOWER OHIO VALLEY
REGION...WITH MEAN STORM MOTIONS OF 15 TO 20 KT. SFC MESOANALYSIS
DEPICTS A WELL-DEFINED COLD POOL OVER MIDDLE TN WITH AN ATTENDANT
MESOHIGH AND SFC PRESSURE RISES AROUND 2 MB IN 2 HOURS. DOWNSTREAM
OF ONGOING CONVECTION...THE MESOSCALE ENVIRONMENT IS CHARACTERIZED
BY UNCAPPED MLCAPE VALUES OF 2000-2500 J/KG AND PWAT VALUES OF 2.0
TO 2.3 INCHES. CONVERGENCE AT THE LEADING EDGE OF THE WWD-EXPANDING
COLD POOL JUXTAPOSED WITH THE AFOREMENTIONED THERMODYNAMIC
PARAMETERS WILL FOSTER CONTINUED WWD CONVECTIVE PROPAGATION INTO THE
LATE AFTERNOON AND EARLY EVENING AS CONVECTION REGENERATES
DOWNSTREAM. DCAPE VALUES IN EXCESS OF 1000 J/KG IN MANY AREAS WILL
SUPPORT STRONG DOWNDRAFTS AND THE POTENTIAL FOR STRONG OR POSSIBLY
DMGG SFC WINDS...WITH THE THREAT ENHANCED BY THE MESOSCALE
CIRCULATION ATTENDANT TO THE CONVECTIVE SYSTEM. AFFIRMING THIS
POTENTIAL...AN EARLIER GUST TO 64 KT WAS MEASURED AT BOWLING GREEN
KY IN ASSOCIATION WITH MORE CELLULAR CONVECTION OVER THE NRN FLANK
OF THE SYSTEM. HOWEVER...MEMPHIS VWP DATA INDICATE WEAK VERTICAL
WIND SHEAR DOWNSTREAM OF ONGOING ACTIVITY...WHICH WILL LIKELY
INHIBIT THE POTENTIAL FOR SUSTENANCE OF A MORE ORGANIZED CONVECTIVE
SYSTEM AND ATTENDANT SVR THREAT. AFTER 01Z...STABILIZATION OWING TO
NOCTURNAL COOLING WITHIN THE BOUNDARY LAYER WILL LIKELY RESULT IN A
DECREASING TREND OF ANY ONGOING CONVECTION.

..COHEN.. 07/21/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...OHX...PAH...MEG...

LAT...LON 36408937 36898890 37058830 37108763 36808737 36338777
35838804 35128821 34668853 34508952 34869013 35568987
36408937

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