DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 130550
SWODY2
SPC AC 130548

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT SAT OCT 13 2012

VALID 141200Z - 151200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE OH AND TN
VALLEYS...

...OH AND TN VALLEYS...
AN UPPER-LEVEL TROUGH OVER THE CNTRL AND SRN PLAINS SATURDAY NIGHT
WILL DEAMPLIFY AND MOVE EWD INTO THE MID MS VALLEY SUNDAY. A LINE OF
ELEVATED THUNDERSTORMS SHOULD BE ONGOING AT THE BEGINNING OF THE
PERIOD ACROSS THE MID MS VALLEY JUST AHEAD OF THE UPPER-LEVEL TROUGH
AXIS AND ON THE WRN EDGE OF A PRONOUNCED LOW-LEVEL JET CENTERED IN
THE LOWER OH VALLEY. MODEL FORECASTS KEEP THE CONVECTION NEAR THE
UPPER-LEVEL TROUGH GOING THROUGHOUT THE DAY WITH NEW CELLS
INITIATING AS INSTABILITY INCREASES. WARMING SFC TEMPS AROUND MIDDAY
SHOULD ENABLE THE CONVECTION TO BECOME SFC-BASED. ADDITIONAL STORM
DEVELOPMENT SHOULD TAKE PLACE FURTHER TO THE EAST IN IND AND WCNTRL
KY ON THE ERN EDGE OF MODERATE INSTABILITY. THESE STORMS MAY
ORGANIZE INTO A LINE MOVING ACROSS WRN OH...CNTRL KY AND MIDDLE TN
DURING THE LATE AFTERNOON AND EARLY EVENING.

FORECAST SOUNDINGS AT 00Z/MONDAY NEAR PADUCAH AND MEMPHIS SHOW
MLCAPE AROUND 1500 J/KG WITH ABOUT 40 KT OF DEEP LAYER SHEAR. THIS
COMBINATION OF SHEAR AND INSTABILITY SHOULD BE SUFFICIENT FOR SEVERE
STORMS. IN ADDITION...FORECAST SOUNDINGS SHOW STEEP LOW-LEVEL LAPSE
RATES WITH 30 KT OF FLOW JUST ABOVE THE SFC SUGGESTING A WIND DAMAGE
THREAT WILL BE POSSIBLE. HAIL MAY ALSO OCCUR WITH CONVECTION BENEATH
THE TROUGH IN THE LOWER OH VALLEY WHERE 500 MB TEMPS ARE FORECAST TO
BE AROUND -14C. FURTHER TO THE EAST IN THE CORRIDOR FROM CINCINNATI
TO NASHVILLE...SEVERE THUNDERSTORMS WILL ALSO BE POSSIBLE MAINLY DUE
TO THE STRONG LOW-LEVEL FLOW AND ENHANCED DEEP LAYER SHEAR
ASSOCIATED WITH A 50 TO 65 KT MID-LEVEL JET. THE MODELS SUGGEST A
LINE OF STORMS WILL DEVELOP ALONG THE LEADING EDGE OF LARGE-SCALE
ASCENT AND MOVE INTO THE WRN APPALACHIAN MTNS SUNDAY EVENING.
ALTHOUGH WIND DAMAGE WILL BE POSSIBLE IF A LINE
DEVELOPS...INSTABILITY IS FORECAST TO BE WEAKER THAN IN AREAS TO THE
WEST SUGGESTING THE THREAT MAY BE MORE CONDITIONAL THERE.

...LOWER TO MID MS VALLEY...
THE SRN EXTENT OF AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD
ACROSS THE ARKLATEX INTO THE LOWER TO MID MS VALLEY ON SUNDAY.
BENEATH THE TROUGH...A SSW TO NNE ORIENTED CORRIDOR OF INSTABILITY
SHOULD BE IN PLACE FROM THE ARKLATEX INTO THE LOWER OH VALLEY. THE
MODELS FORECAST ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT ON
THE ERN EDGE OF MODERATE INSTABILITY AND ON THE SWRN EDGE OF THE
LOW-LEVEL JET. FORECAST SOUNDINGS LATE SUNDAY AFTERNOON WHERE THE
CONVECTIVE POTENTIAL APPEARS HIGHEST IN NRN MS AND NRN LA SHOW
MLCAPE VALUES OF 500 TO 1000 J/KG WITH ABOUT 30 KT OF DEEP LAYER
SHEAR. THIS COMBINATION OF SHEAR AND INSTABILITY MAY BE ENOUGH FOR A
MARGINAL SEVERE THREAT. STEEP LOW-LEVEL LAPSE RATES ALONG WITH ABOUT
20 KT OF FLOW JUST ABOVE THE SFC MAY RESULT IN AN ISOLATED WIND
DAMAGE THREAT CONCENTRATED JUST AFTER PEAK HEATING.

..BROYLES.. 10/13/2012

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