SWODY2
SPC AC 130558
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT WED APR 13 2011
VALID 141200Z - 151200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SE KS...ERN
OK...FAR SW MO AND FAR NW AR...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS...SRN PLAINS...MID-MO VALLEY...OZARKS AND ARKLATEX...
...REGIONAL OUTBREAK OF SEVERE STORMS AND POSSIBLY TORNADOES ACROSS
PARTS OF THE SRN AND CNTRL PLAINS THURSDAY AFTERNOON AND EVENING...
...SRN PLAINS/CNTRL PLAINS/OZARKS/MID-MO VALLEY...
AN IMPRESSIVE NEGATIVELY-TILTED UPPER-LEVEL TROUGH IS FORECAST TO
CLOSE OFF OVER THE CNTRL HIGH PLAINS THURSDAY. THE EXIT REGION OF A
70 TO 80 KT MID-LEVEL JET ROUNDING THE BASE OF THE TROUGH WILL
CREATE STRONG DEEP LAYER SHEAR PROFILES ACROSS THE REGION CREATING
AN ENVIRONMENT FAVORABLE FOR SEVERE STORM DEVELOPMENT. AT THE
SFC...A WELL-DEVELOPED LOW IS FORECAST TO DEEPEN QUICKLY ACROSS
CNTRL KS AT MIDDAY MOVING NWD INTO NEB. THUNDERSTORM INITIATION
SHOULD FIRST OCCUR NEAR AND TO THE NORTH OF THE SFC LOW DURING THE
AFTERNOON WHERE STRONG LOW-LEVEL CONVERGENCE AND COLD TEMPS ALOFT
SHOULD RESULT IN A LARGE HAIL THREAT. THE MODELS ARE CONSISTENT
DEVELOPING STRONG CONVECTION DURING THE LATE AFTERNOON SEWD INTO
CNTRL TO ERN KS AND ECNTRL OK ALONG THE WRN EDGE OF AN AXIS OF
MODERATE INSTABILITY. THE STORMS SHOULD INITIATE JUST TO THE EAST OF
A DRYLINE ORIENTED NORTH TO SOUTH ALONG THE I-35 CORRIDOR.
FORECAST SOUNDINGS ALONG THE INSTABILITY AXIS AT 00Z FRIDAY SHOW
MLCAPE VALUES FROM 1500 J/KG IN ECNTRL KS TO 2500 TO 3000 J/KG IN
ECNTRL OK. THIS COMBINED WITH 0-6 KM SHEAR VALUES OF 50 TO 65 KT
WILL CREATE A THERMODYNAMIC AND SHEAR ENVIRONMENT FAVORABLE FOR
SUPERCELLS AND LARGE HAIL ESPECIALLY ACROSS THE MODERATE RISK AREA
IN SE KS...ERN OK...FAR NW AR AND FAR SW MO. THE GREATEST SEVERE
THREAT COVERAGE SHOULD OCCUR ON THE NOSE OF A PLUME OF STEEP
MID-LEVEL LAPSE RATES WHICH COMBINED WITH THE MODERATE INSTABILITY
AND STRONG DEEP LAYER SHEAR WILL BE FAVORABLE FOR VERY LARGE HAIL
WITH THE MORE DOMINANT SUPERCELLS. TORNADOES WILL ALSO BE POSSIBLE
ESPECIALLY AS THE LOW-LEVEL JET STRENGTHENS DURING THE EARLY
EVENING. FORECAST SOUNDINGS IN ERN OK FROM 00Z TO 03Z SHOW 0-3 KM
STORM RELATIVELY HELICITIES OF 350 TO 450 M2/S2 WHICH WILL MAKE AN
ISOLATED THREAT FOR STRONG TORNADOES POSSIBLE. HOWEVER...THIS THREAT
SHOULD BE CONDITIONAL UPON MOISTURE RETURN AND STORM MODE.
SQUALL-LINE DEVELOPMENT INSTEAD OF THE TENDENCY FOR DISCRETE
CONVECTION WOULD RESULT IN MORE OF A WIND DAMAGE THREAT.
FURTHER SOUTH ACROSS NE TX...FORECAST SOUNDINGS AT 21Z TO 00Z SHOW A
STOUT CAPPING INVERSION WHICH IS EXPECTED TO HOLD FOR MUCH OF THE
AFTERNOON AND EVENING. FOR THIS REASON...THE SEVERE THREAT SHOULD
DROP OFF QUICKLY WITH SWD EXTENT IN NE TX. DURING THE EVENING AND
OVERNIGHT PERIOD...THE MODELS ARE CONSISTENT WITH DEVELOPING AN MCS
IN THE OZARKS AND DRIVING THIS FEATURE EWD INTO THE LOWER TO MID MS
VALLEY. ALTHOUGH SEVERE THREAT COVERAGE SHOULD DECREASE DURING THE
LATE EVENING AND OVERNIGHT PERIOD...A THREAT FOR HAIL AND ISOLATED
WIND DAMAGE MAY CONTINUE AS FAR EAST AS SCNTRL MO AND ECNTRL AR
WHERE SFC DEWPOINTS SHOULD BE IN THE LOWER 60S F AND 40 TO 50 KTS OF
LOW-LEVEL FLOW IS FORECAST.
..BROYLES.. 04/13/2011
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