[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 101621
SWOMCD
SPC MCD 101620
WVZ000-VAZ000-TNZ000-KYZ000-ALZ000-101745-

MESOSCALE DISCUSSION 1732
NWS STORM PREDICTION CENTER NORMAN OK
1120 AM CDT FRI AUG 10 2012

AREAS AFFECTED...PARTS OF CNTRL/ERN KY...MIDDLE/ERN TN...AND SRN
WEST VIRGINIA... INTO THE CREST OF THE APPALACHIANS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 101620Z - 101745Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN INCREASE IN THUNDERSTORM ACTIVITY IS EXPECTED ACROSS
THE REGION THROUGH THE 18-20Z TIME FRAME.  THE SEVERE THREAT MAY NOT
BE COMPLETELY NEGLIGIBLE...BUT THE ENVIRONMENT APPEARS TO SUPPORT
ONLY LOW POTENTIAL FOR ORGANIZED SEVERE STORMS.  A WATCH IS NOT
ANTICIPATED IN THE NEAR TERM...BUT TRENDS WILL CONTINUE TO BE
MONITORED.

DISCUSSION...BREAKS IN THE OVERCAST ARE ALLOWING INCREASING
INSOLATION AND BOUNDARY LAYER DESTABILIZATION AHEAD OF THE SURFACE
FRONT NOW ADVANCING SOUTHEASTWARD THROUGH THE LOWER OHIO VALLEY.
THIS IS MOSTLY TO THE SOUTH AND EAST OF THE MID-LEVEL COLD CORE OF
THE GREAT LAKES UPPER LOW...AND FORECAST SOUNDINGS SUGGEST THAT A
RELATIVELY WARM MID-LEVEL LAYER /AROUND 500 MB/ WILL LIMIT THE
DEGREE OF DESTABILIZATION THROUGH THE AFTERNOON HOURS.  STILL...
DEEPENING CONVECTIVE DEVELOPMENT IS ALREADY EVIDENT...AND SUFFICIENT
INSTABILITY PROBABLY WILL DEVELOP THROUGH THE NEXT FEW HOURS TO
SUPPORT INCREASING THUNDERSTORM ACTIVITY ACROSS PARTS OF THE
TENNESSEE VALLEY AND CUMBERLAND PLATEAU INTO THE WESTERN SLOPES OF
THE CENTRAL APPALACHIANS.  THIS COULD BE AIDED BY FORCING FOR UPWARD
VERTICAL MOTION DOWNSTREAM OF A SHORT WAVE IMPULSE PIVOTING AROUND
THE SOUTHERN PERIPHERY OF THE LOW...AND MODEST DEEP LAYER SHEAR
BENEATH 30-40+ KT WESTERLY 500 MB FLOW.

ALTHOUGH THE DEEP LAYER SHEAR IS SUPPORTIVE OF UPDRAFT ROTATION AND
ORGANIZED CONVECTIVE DEVELOPMENT...THE RELATIVELY WARM MID-LEVEL
TEMPERATURES AND RATHER MODEST CAPE AND LOW-LEVEL WIND FIELDS/SHEAR
DO NOT APPEAR PARTICULARLY CONDUCIVE TO DAMAGING WIND POTENTIAL.
HOWEVER...GIVEN PRECIPITABLE WATER UP TO AROUND 1.75 INCHES...AND
AMBIENT DEEP LAYER WESTERLY MEAN FLOW ON THE ORDER OF 20-30
KT...LOCALIZED DOWNBURSTS AND POTENTIALLY DAMAGING WIND GUSTS MAY
NOT BE COMPLETELY OUT OF THE QUESTION IN STRONGER STORMS.

..KERR/HART.. 08/10/2012

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

ATTN...WFO...RNK...RLX...MRX...JKL...LMK...OHX...HUN...

LAT...LON   36568563 37748407 38128238 37818069 36418199 35088514
            34978745 35288796 36568563


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