SPC AC 051242
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0742 AM CDT TUE MAY 05 2009
   
   VALID 051300Z - 061200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF NRN TX AND SRN
   OK...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF TX/OK ACROSS
   THE CENTRAL GULF COAST INTO THE CAROLINAS...
   
   ...SRN PLAINS TOWARDS THE LOWER MS RIVER VALLEY...
   BROAD MID/UPPER LEVEL TROUGH IS FORECAST TO OVERSPREAD THE CENTRAL
   PLAINS THROUGH THE PERIOD.  AS THIS OCCURS...SURFACE WARM FRONT
   EXTENDING FROM SRN MS INTO CENTRAL TX AT 12Z WILL BE SHIFTED
   STEADILY NWD INTO NWRN TX AND CENTRAL LA BY THE LATE AFTERNOON.  IN
   ADDITION...WELL DEFINED DRY LINE IS EXPECTED TO BECOME ESTABLISHED
   ACROSS WRN TX WITH MOST MODEL GUIDANCE DEVELOPING TRIPLE POINT
   NEAR/NW OF ABI AND A DRY LINE BULGING JUST SOUTH OF THIS INTO
   WRN/NWRN TX.  WARM FRONT WILL BECOME BETTER DEFINED E-W ACROSS NRN
   TX INTO NRN LA LATER THIS EVENING/TONIGHT.
   
   ELEVATED THUNDERSTORMS ARE EXPECTED TO INCREASE ALONG NOSE OF STRONG
   SWLY LLJ BEING SAMPLED BY 50 KT 1 KM WINDS AT JTN PROFILER THIS
   MORNING.  THIS ACTIVITY WILL LIKELY INCREASE ALONG AND NORTH OF THE
   RED RIVER THROUGH THE MORNING AND POSSIBLY EVOLVE INTO AN MCS TODAY
   AS IT SHIFTS EWD ACROSS OK/FAR NRN TX WITH A THREAT OF LARGE HAIL
   FROM THE STRONGER CORES.  ADDITIONAL DEVELOPMENT IS EXPECTED ALONG
   THE WARM FRONT FROM ERN TX INTO THE LOWER MS RIVER VALLEY AS WARM
   SECTOR BECOMES VERY UNSTABLE AND WEAKLY CAPPED BY THE MID TO LATE
   AFTERNOON.  SHEAR WILL BE MARGINAL...BUT STILL SUFFICIENT FOR
   SUPERCELLS WITH THIS DEVELOPMENT.
   
   ATTENTION WILL THEN SHIFT ALONG THE DRY LINE WHERE AFTERNOON HEATING
   AND INCREASING CONVERGENCE MAY BREAK CAP OVER NWRN TX. 
   HOWEVER...SHOULD HEATING BE HINDERED TOO MUCH OVER WRN TX BY HIGH
   CLOUDINESS NOW SPREADING ESEWD OUT OF THE SRN ROCKIES AND/OR OUTFLOW
   FROM MORNING ACTIVITY LIMIT NWWD PUSH TO WARM FRONT INTO NWRN TX
   TODAY...CAP COULD HOLD /AS FORECAST BY THE 06Z NAM/.  THUS...HIGHER
   PROBABILITIES ARE MORE CONDITIONAL INTO NWRN TX. EXPECT CAP WILL
   WEAKEN SUFFICIENTLY FOR AT LEAST AN ISOLATED SUPERCELL OR TWO LATE
   IN THE DAY.  STORMS SHOULD BECOME SEVERE QUICKLY GIVEN EXTREME
   INSTABILITY WITH VERY FAVORABLE PARAMETERS FOR SIGNIFICANT HAIL AND
   POSSIBLE TORNADOES FROM SLOW MOVING SSEWD SUPERCELLS.
   
   LLJ IS FORECAST TO INTENSIFY AGAIN OVER NWRN TX AFTER DARK AND
   RESULT IN VIGOROUS...SLIGHTLY ELEVATED THUNDERSTORM DEVELOPMENT OVER
   SRN OK/NRN TX LATER THIS EVENING.  LARGE HAIL...SOME OF WHICH COULD
   BE SIGNIFICANT...WOULD ACCOMPANY THESE STORMS.  ALSO...VERY STRONG
   SHEAR WILL FAVOR SUPERCELLS WITH ATTENDANT TORNADO THREAT ALONG
   INCREASING LLJ THIS EVENING FROM STORMS NEAR THE WARM FRONT. 
   ACTIVITY MAY ORGANIZE INTO A BOW ECHO AS STORMS RIDE ALONG AND JUST
   NORTH OF SURFACE WARM FRONT INTO/ACROSS THE ARKLATEX REGION LATER
   TONIGHT.
   
   ...FAR SERN VA/SOUTHEAST AND SRN PARTS OF CENTRAL GULF COAST...
   ANOTHER ACTIVE DAY ACROSS THIS REGION AS SURFACE FRONT REMAINS
   STALLED FROM SRN MS INTO CENTRAL GA AND THEN NEWD ACROSS THE
   CENTRAL/SRN CAROLINAS/SERN VA.  ONGOING DEVELOPMENT OVER SC IS TIED
   TO SHORTWAVE TROUGH EVIDENT ON WV IMAGERY NOW MOVING ACROSS THE SRN
   ROCKIES.  THIS ACTIVITY MAY INCREASE THROUGH THE MORNING IF AIR MASS
   CAN DESTABILIZE OVER NERN SC/ERN NC.  OTHER STORMS SHOULD INCREASE
   THROUGH THE DAY AS WARM SECTOR BECOMES MODERATELY UNSTABLE NEAR THE
   BOUNDARY FROM THE CENTRAL GULF COAST  INTO THE EASTERN CAROLINAS. 
   20 KT WLY MID LEVEL FLOW ACROSS THE GULF COAST STATES SHOULD SUPPORT
   25-35 KT EFFECTIVE SHEAR AND SOME ORGANIZATION INTO CLUSTERS/LINES. 
   ISOLATED LARGE HAIL AND DAMAGING WINDS SHOULD ACCOMPANY THIS
   ACTIVITY.  SHEAR WILL BE SLIGHTLY STRONGER AND SEVERE THREAT A BIT
   GREATER FROM SC NWD TOWARDS THE SRN MID ATLANTIC STATES ASSOCIATED
   WITH AFOREMENTIONED SHORTWAVE TROUGH...AS 30-40 KT EFFECTIVE SHEAR
   SUSTAINS ORGANIZED LINES AND POSSIBLY A FEW SUPERCELLS.  SEVERE
   THREAT SHOULD WANE WITH N-NEWD EXTENT AS SURFACE FRONT HOLDS OVER
   MUCH OF VA AND CENTRAL NC.
   
   ..EVANS/GARNER.. 05/05/2009
   
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