SWODY1
SPC AC 190604
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0104 AM CDT WED MAY 19 2010
VALID 191200Z - 201200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF OKLAHOMA AND
ADJACENT PARTS OF NORTH TEXAS AND WESTERN ARKANSAS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTHWEST KANSAS TO
NORTHERN TEXAS...PARTS OF SOUTHWEST ARKANSAS AND NORTHERN
LOUISIANA...
...SYNOPSIS...
A POTENTIALLY SIGNIFICANT SEVERE WEATHER OUTBREAK APPEARS
INCREASINGLY LIKELY ACROSS PARTS OF OKLAHOMA...SOUTHERN KANSAS...AND
NORTHERN TEXAS LATER TODAY. STRONG TO SEVERE STORMS WILL ALSO BE
POSSIBLE SOUTH AND EAST FROM THESE AREAS...FROM ARKANSAS TO
LOUISIANA.
...SRN PLAINS INTO ARKLATEX...
A LARGE DEEP-LAYER CYCLONE WILL EVOLVE ACROSS CO/WY EARLY TODAY AND
THEN DRIFT EAST ACROSS THE CENTRAL PLAINS STATES THROUGH TONIGHT.
WIDESPREAD THUNDERSTORMS WERE ALREADY OCCURRING AHEAD OF THIS
DEVELOPING LOW AS WARM ADVECTION AND LARGE SCALE ASCENT ACT ON A
MOIST AND MODERATELY UNSTABLE AIR MASS FROM TX TO KS. PRECIPITATION
AND RESIDUAL CLOUDINESS FROM THE STORMS NOW DEVELOPING ACROSS NRN OK
AND KS WILL ACT TO ESTABLISH A NW-SE ORIENTED WARM FRONT ACROSS OK
LATER THIS MORNING.
AS THE UPPER LOW EMERGES OVER WRN KS LATER THIS AFTERNOON... TRIPLE
POINT SURFACE LOW IS FORECAST TO STRENGTHEN INVOF OK PANHANDLE AS
DRYLINE SHARPENS AND SPREADS EAST FROM ERN TX PANHANDLE. BELT OF
40-50KT WLY CYCLONIC MID LEVEL FLOW ATOP SLY/SELY LOW LEVEL FLOW
ACROSS THE WARM SECTOR WILL CONTRIBUTE TO STRONG EFFECTIVE SHEAR AOA
40KT. DIURNAL HEATING AND GRADUAL MOISTENING OF THE BOUNDARY LAYER
SHOULD RESULT IN AN INCREASINGLY UNSTABLE WARM SECTOR WITH WEAKLY
CAPPED MLCAPE OF 1500-2000 J PER KG BY AFTERNOON.
GIVEN WEAK INHIBITION AND PERSISTENT MODEST FORCING FOR ASCENT
EXPECT WARM SECTOR STORM INITIATION EARLIER THAN LATER. DISCRETE
SUPERCELLS SHOULD EVOLVE QUICKLY AHEAD OF THE DRY LINE IN WRN
OK...WITH ADDITIONAL STORMS POSSIBLE NEAR/ALONG RESIDUAL OUTFLOWS
AND NEAR SURFACE WARM FRONT...FROM NRN/CNTRL OK TO NRN TX/AR/LA.
EFFECTIVE HELICITY IN THE RANGE OF 200-300 M2/S2...AND RELATIVELY
HIGH BOUNDARY LAYER RH/LOW LFC ACROSS CNTRL OK...SHOULD RESULT IN AN
ENHANCED STRONG TORNADO POTENTIAL ACROSS THIS AREA FROM LATE
AFTERNOON INTO EARLY EVENING.
UNLIKE MAY 10...WEAKER FLOW REGIME RESULTS IN SLOWER STORM/BUNKERS
CELL MOTION OF ENE AROUND 25 KT...AS OPPOSED TO ENE AT 50KT.
FURTHERMORE...INSTABILITY APPEARS A BIT WEAKER. NONETHELESS...A
POTENTIALLY VOLATILE STRONG TORNADO SITUATION MAY EVOLVE ACROSS
PORTIONS OF CNTRL OK DURING THE AFTERNOON...POSSIBLY MOVING TOWARD
ERN OK INTO THE EVENING. THIS IS A RELATIVELY LIMITED GEOGRAPHIC
AREA OF GREATER TORNADO POTENTIAL. COMBINED WITH THE POSSIBILITY
THAT FORECAST CERTAINTY CAN INCREASE WITH THE LIGHT OF DAY...GREATER
TORNADO PROBABILITIES...AND AN UPGRADE TO HIGH RISK...MAY OCCUR IN
SUBSEQUENT OUTLOOKS.
IN ADDITION TO THE TORNADO POTENTIAL...VERY LARGE HAIL AND LOCALLY
DAMAGING DOWNBURST/OUTFLOW WINDS WILL ACCOMPANY STORM DEVELOPMENT
ACROSS A LARGER AREA FROM SRN KS EXTENDING INTO TX...AR AND LA FROM
AFTERNOON THROUGH THE EVENING.
AS CONVECTION CONGEALS OVER ERN OK THROUGH THE EVENING...LIFT AND
SUSTAINED INSTABILITY ACROSS THE WARM FRONT...AND UPSCALE EVOLUTION
IN STRONGLY SHEARED FLOW...WILL CONTRIBUTE TO FORWARD PROPAGATING
MCS/SQUALL LINE WITH DAMAGING WINDS SPREADING SEWD TOWARD AR AND THE
ARKLATEX THROUGH THURSDAY MORNING.
...ERN NC...
GREATER LOW LEVEL MOISTURE ALONG A RESIDUAL FRONTAL SEGMENT ACROSS
SERN NC...COUPLED WITH DIURNAL HEATING...SHOULD CONTRIBUTE TO
MODERATE INSTABILITY LATER TODAY. STRENGTHENING MID LEVEL WLY FLOW
AROUND 40KT AND DPVA ASSOCIATED WITH PASSAGE OF SHORT WAVE TROUGH TO
THE NORTH MAY BE SUFFICIENT FOR A FEW VIGOROUS STORMS ACROSS THE
IMMEDIATE COASTAL ZONE. A COUPLE HAIL/WIND EVENTS APPEAR POSSIBLE
WITH THIS ACTIVITY.
..CARBIN/ROGERS.. 05/19/2010
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