ACUS01 KWNS 110550
SWODY1
SPC AC 110548
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT WED MAY 11 2011
VALID 111200Z - 121200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF WCNTRL KS AND
WRN OK...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...CNTRL PLAINS AND MID-MO VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WRN SC AND ERN
GA...
...SEVERE WEATHER EPISODE WILL BE LIKELY ACROSS THE SRN AND CNTRL
PLAINS TODAY WITH AN ISOLATED THREAT FOR STRONG TORNADOES...
...SRN AND CNTRL PLAINS...
AN UPPER-LEVEL LOW OVER THE FOUR CORNERS REGION WILL MOVE EWD ACROSS
THE SRN ROCKIES AND DECELERATE AS THE SYSTEM MOVES INTO THE CNTRL
PLAINS THIS AFTERNOON. AHEAD OF THE SYSTEM...A WELL-DEVELOPED
LOW-LEVEL JET WILL BE IN PLACE ACROSS THE SRN AND CNTRL PLAINS WITH
AN AXIS OF MODERATE TO STRONG INSTABILITY LOCATED FROM CNTRL AND NRN
TX EXTENDING NWD ACROSS OK AND KS. MODEL FORECASTS DEVELOP A CLUSTER
OF STRONG THUNDERSTORMS THIS MORNING ACROSS THE TX HILL COUNTRY
ASSOCIATED WITH A SUBTLE SHORTWAVE TROUGH MOVING NEWD ACROSS THE
REGION. THIS ACTIVITY MAY HAVE A HAIL THREAT AS THE CONVECTION MOVES
INTO THE AXIS OF THE LOW-LEVEL JET ACROSS EAST AND NORTH TX THIS
AFTERNOON. FURTHER TO THE NORTH...ACROSS WCNTRL OK AND WCNTRL
KS...THE AIRMASS SHOULD REMAIN UNDISTURBED THROUGH EARLY AFTERNOON
AS A DRYLINE SHARPENS ACROSS WRN KS AND WRN OK. AS LOW-LEVEL
CONVERGENCE INCREASES ALONG THE DRYLINE AND THE CAP WEAKENS THIS
AFTERNOON...SCATTERED THUNDERSTORM INITIATION SHOULD TAKE PLACE ON
THE WRN EDGE OF THE MODERATE RISK AREA. INCREASING DEEP LAYER SHEAR
ASSOCIATED WITH AN APPROACHING MID-LEVEL JET AND MODERATE
INSTABILITY SHOULD BE FAVORABLE FOR SUPERCELL DEVELOPMENT. AS
SUPERCELLS RAPIDLY DEVELOP...A HIGHER-END SEVERE WEATHER EVENT
SHOULD UNFOLD LATE THIS AFTERNOON INTO THE EVENING ACROSS THE SRN
AND CNTRL PLAINS.
CONVECTIVE INITIATION SHOULD TAKE PLACE FIRST THIS AFTERNOON ACROSS
NRN KS ALONG A WARM FRONT EXTENDING ENEWD FROM SFC LOW IN WRN KS.
FORECAST SOUNDINGS FROM GOODLAND KS EWD TO SALINA KS AT 21Z SHOW
MLCAPE VALUES OF 1500 TO 2500 J/KG AND 0-6 KM SHEAR VALUES AROUND 40
KT. THIS COMBINED WITH COLD TEMPS ALOFT ASSOCIATED WITH THE
UPPER-LEVEL LOW TO THE WEST...SHOULD PROVIDE CONDITIONS FAVORABLE
FOR LARGE HAIL AS SUPERCELLS AND/OR BOWING LINE-SEGMENTS ORGANIZE
DURING THE LATE AFTERNOON. FURTHER SOUTH ALONG THE
DRYLINE...FORECAST SOUNDINGS AT 21Z TO 00Z SHOW MLCAPE VALUES OF
2000 TO 3000 J/KG WITH 0-6 M SHEAR VALUES AROUND 40 KT. DEEP LAYER
SHEAR SHOULD INCREASE BY 00Z AS A 60 TO 70 KT MID-LEVEL JET MOVES
INTO THE SRN PLAINS. THIS COMBINED WITH 700 TO 500 MB LAPSE RATES OF
8.0 TO 8.5 C/KM SHOULD BE VERY FAVORABLE FOR LARGE HAIL. A THREAT
FOR 2 INCH OR GREATER HAIL SHOULD EXIST WITH THE MORE INTENSE
SUPERCELLS. IN ADDITION...LOW-LEVEL SHEAR WILL ALSO INCREASE DURING
THE EARLY EVENING AS A 35 TO 50 KT LOW-LEVEL JET BECOMES FOCUSED
ACROSS CNTRL OK AND SRN KS. THE GREATEST THREAT FOR TORNADOES SHOULD
EXIST TO THE WEST OF THE JET CENTER IN WRN OK AND WCNTRL KS AS
SUPERCELLS MATURE DURING THE EARLY EVENING. AN ISOLATED THREAT FOR
STRONG TORNADOES MAY EXIST WITH THE MORE DOMINANT SUPERCELLS.
THE MAIN UNCERTAINTY WITH THE FORECAST IS STORM COVERAGE. MOST OF
THE MODELS KEEP CONVECTIVE COVERAGE ACROSS WRN OK AND WRN KS
RELATIVELY ISOLATED. THIS IS PROBABLY DUE TO THE UPPER-LEVEL LOW
WHICH IS FORECAST TO SLOW DOWN CONSIDERABLY...KEEPING MOST OF THE
LARGE-SCALE ASCENT WEST OF THE DRYLINE. AT THIS POINT...THE NAM
SOLUTION AT 00Z APPEARS REASONABLE SUGGESTING THE STORMS MAY TEND TO
REMAIN WIDELY GAPPED. IN SPITE OF THIS...THE SYNOPTIC PATTERN WITH A
STRONG LOW-LEVEL JET RESPONSE...EJECTING MID-LEVEL JET AND
WELL-DEVELOPED DRYLINE SHOULD RESULT IN A HIGHER-END SEVERE THREAT.
FOR THIS REASON...WILL MAINTAIN A MODERATE RISK ACROSS WCNTRL KS AND
WRN OK.
...SRN APPALACHIAN MTNS AND CAROLINAS...
NNWLY FLOW WILL BE IN PLACE AGAIN TODAY FROM THE CNTRL APPALACHIAN
MTNS SWD INTO THE CAROLINAS. SFC HEATING AND SFC DEWPOINTS AROUND 70
F SHOULD RESULT IN MODERATE TO STRONG DESTABILIZATION BY THIS
AFTERNOON. SCATTERED THUNDERSTORMS APPEAR LIKELY TO DEVELOP THIS
AFTERNOON IN THE WRN CAROLINAS AS A SUBTLE SHORTWAVE TROUGH MOVES
SSEWD ACROSS THE REGION. MLCAPE VALUES OF 2500 TO 3500 J/KG ALONG
WITH 45 TO 50 KT OF DEEP LAYER SHEAR SHOULD BE SUFFICIENT FOR
SUPERCELL DEVELOPMENT. ANY SUPERCELL THAT DEVELOPS SHOULD CONTAIN AN
ISOLATED THREAT FOR LARGE HAIL AND WIND DAMAGE.
...MID TO UPPER MS VALLEY...
AN AXIS OF MODERATE INSTABILITY SHOULD EXIST FROM THE LOWER OH
VALLEY NWD INTO THE UPPER MS VALLEY WHERE MLCAPE VALUES SHOULD BE IN
THE 3000 TO 4000 J/KG RANGE BY MID-AFTERNOON. ALTHOUGH LARGE-SCALE
ASCENT SHOULD REMAIN RELATIVELY WEAK...A FEW STORMS MAY INITIATE
FROM SRN MN AND ERN IA EWD ACROSS WI AND NRN IL. THE STRONG
INSTABILITY AND STEEP LOW-LEVEL LAPSE RATES COULD RESULT IN A
MARGINAL WIND DAMAGE THREAT WITH HAIL ALSO POSSIBLE WITH THE MORE
INTENSE CELLS.
..BROYLES/STOPKOTTE.. 05/11/2011
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