[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 050132
SWOMCD
SPC MCD 050132
TNZ000-KYZ000-ALZ000-MSZ000-ILZ000-MOZ000-ARZ000-OKZ000-KSZ000-050300-

MESOSCALE DISCUSSION 1780
NWS STORM PREDICTION CENTER NORMAN OK
0832 PM CDT TUE AUG 04 2009

AREAS AFFECTED...PORTIONS MIDDLE-WRN TN...WRN KY...SERN MO...NERN
AR...EXTREME NERN OK...EXTREME SERN KS.

CONCERNING...SEVERE THUNDERSTORM WATCH 658...659...661...

VALID 050132Z - 050300Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
658...659...661...CONTINUES.

CONCERN FOR ORGANIZED SVR POTENTIAL CONTINUES WITH MCS MOVING SEWD
35-40 KT FROM WRN KY INTO PORTIONS WRN/MIDDLE TN.  COUNTIES IN
POTENTIALLY AFFECTED PORTIONS WW 659 MAY BE EXTENDED BEYOND
SCHEDULED 02Z EXPIRATION.

SEVERAL REPORTS OF DAMAGING GUSTS HAVE BEEN RECEIVED DURING PAST 1-2
HOURS INVOF TN/KY BORDER...ALTHOUGH MEASURED WINDS HAVE BEEN
SUBSEVERE AT SFC OBS SITES SUCH AS HOP AND CKV.  APEX OF THIS SYSTEM
WILL MOVE SEWD TOWARD BNA AREA AND ACROSS WRN/SRN PORTIONS MIDDLE TN
WITH POTENTIAL FOR OCCASIONAL DAMAGING GUSTS.  OUTFLOW BOUNDARY FROM
EARLIER/EASTERN MCS IS EVIDENT AT 01Z FROM NEAR CHA NWWD CROSS
WILLIAMSON COUNTY TO ERN DICKSON COUNTY TN.  00Z BNA RAOB MEASURED
ABOUT 2 KFT DEPTH OF STABLE LAYER ASSOCIATED WITH COLD POOL...AND
EFFECTIVE LIFTED PARCELS WERE ROOTED ABOUT 1/2 KM AGL.  OLDER
OUTFLOW BOUNDARY IS MOVING SWWD 10-15 KT ACROSS THIS REGION AND
AHEAD OF MCS.  RELATED COLD POOL SHOULD BECOME SHALLOWER WITH
WESTWARD EXTENT AND WITH TIME...INCREASING POTENTIAL FOR DAMAGING
GUSTS FROM IMPENDING MCS TO REACH SFC W AND SW OF BNA VERSUS FARTHER
E AND NE.  MLCAPE WILL DIMINISH WITH SWD EXTENT ACROSS NRN AL AND
NERN MS BECAUSE OF COMBINATION OF SFC DIABATIC COOLING...SOMEWHAT
WEAKER LAPSE RATES ALOFT...AND DRY AIR JUST ABOVE SFC.
HOWEVER...THAT DRYING LAYER ALSO MAY FOSTER ENHANCED DCAPE AND
DOWNDRAFT ACCELERATION FOR AS LONG AS MCS MAY PERSIST.  THESE AREAS
WILL BE MONITORED FOR POSSIBLE WW AS CONVECTIVE TRENDS WARRANT.

FARTHER NW...CLUSTER OF STG-SVR TSTMS OVER SERN MO REMAINS IN POCKET
OF FAVORABLY MOIST/UNSTABLE AIR ALONG AND E OF OUTFLOW BOUNDARY FROM
KY/TN COMPLEX.  THIS ACTIVITY LIKEWISE MAY ORGANIZE INTO MCS AND
MOVE SEWD TOWARD PORTIONS WRN TN AND WRN KY.  WIND DAMAGE POTENTIAL
SHOULD DECREASE WITH EWD EXTENT OVER PROGRESSIVELY DEEPER COLD POOL
FROM EARLIER CONVECTION...WITH LARGE HAIL POSSIBLE ON BOTH SIDES OF
OUTFLOW BOUNDARY.  PORTIONS NERN AR AND MO BOOT-HEEL WILL BE
MONITORED FOR POSSIBLE WW...EITHER ANEW OR AS EXTENSION OF WW
658....BEFORE SCHEDULED 03Z EXPIRATION OF WW 658.  POTENTIAL FOR SVR
APPEARS TO BE DIMINISHING WITH TIME...BUT NOT ENTIRELY GONE
YET...ACROSS WRN OZARKS.  SGF RAOB INDICATED FAVORABLE
MOISTURE...INSTABILITY AND DEEP-LAYER SHEAR...BUT FRONTAL LIFT MAY
NOT BE SUFFICIENT TO OVERCOME CINH NOW THAT DIABATIC COOLING HAS
BEGUN IN BOUNDARY LAYER AND HEIGHTS ALOFT ARE RISING.

..EDWARDS.. 08/05/2009

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

ATTN...WFO...MRX...LMK...OHX...HUN...PAH...MEG...LSX...LZK...
SGF...TSA...

LAT...LON   37739093 37618947 37108802 37178733 37348664 36278555
            35008566 34538621 34338726 34458841 34968973 36499093
            36459459 36829512 37169461 37669117 37739093

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