SPC AC 052003
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0303 PM CDT TUE MAY 05 2009
   
   VALID 052000Z - 061200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CAROLINAS WSWWD INTO
   THE SRN PLAINS...
   
   ...SRN OK/N TX EWD INTO THE ARKLATEX...
   CAPPING INVERSION REMAINS IN PLACE ACROSS MUCH OF TX...S OF A WARM
   FRONT LYING W-E ACROSS N TX.  N OF THE FRONT IN A ZONE OF LOW-LEVEL
   WARM ADVECTION...CONVECTION HAS PERSISTED...WITH A BOW ECHO NOW
   CROSSING SERN OK.
   
   MEANWHILE...HEATING CONTINUES ACROSS W TX AHEAD OF THE
   DRYLINE...WITH A DRYLINE/WARM FRONT INTERSECTION NOW INDICATED NW OF
   ABI.  CAPPING IS EXPECTED TO HINDER CONVECTIVE DEVELOPMENT TO SOME
   DEGREE...THOUGH ISOLATED STORMS SHOULD DEVELOP LATE THIS AFTERNOON
   AND EVENING.  GIVEN DEGREE OF INSTABILITY AND FAVORABLE
   SHEAR...THESE STORMS -- WHICH WILL QUICKLY BECOME SUPERCELLULAR --
   WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL. 
   ADDITIONALLY...LOCALLY-DAMAGING WINDS AND/OR ISOLATED TORNADOES WILL
   BE POSSIBLE -- PARTICULARLY NEAR THE WARM FRONT.  WITH CAPPING
   LIKELY TO LIMIT THE NUMBER OF STORMS...WILL DROP THE MDT RISK THIS
   FORECAST BUT MAINTAIN THE PROBABILITY FOR ISOLATED/SIGNIFICANT
   SUPERCELLS.
   
   THIS EVENING...AS A SHORT-WAVE TROUGH CROSSES THE REGION...EXPECT
   STORMS DEVELOPING OVER N TX TO ORGANIZE INTO ONE OR MORE MCS/BOW
   ECHOES -- WHICH SHOULD THEN RIDE ESEWD ALONG THE SURFACE FRONT. 
   FAVORABLE INSTABILITY AND 40-50 KT WLY MID-LEVEL FLOW SUGGESTS THE
   POTENTIAL FOR FAIRLY WIDESPREAD/DAMAGING WINDS ACROSS N TX -- AND
   LATER INTO THE ARKLATEX REGION.
   
   ...CAROLINAS WSWWD INTO SRN GA/SRN AL/SRN MS...
   SHOWERS AND THUNDERSTORMS CONTINUE INVOF A WEAK SURFACE FRONT
   EXTENDING WSWWD ACROSS THE SOUTHEAST...AS WELL AS NEAR SMALLER-SCALE
   BOUNDARIES WITHIN THE WARM SECTOR.  MOIST BOUNDARY LAYER COMBINED
   WITH DAYTIME HEATING HAS YIELDED MODERATE DESTABILIZATION...WHICH
   COMBINED WITH AMPLE SHEAR HAS YIELDED LOCALLY-ORGANIZED/ISOLATED
   SUPERCELL STORMS.  LOW-LEVEL SHEAR IS SUPPORTIVE OF AN ISOLATED
   TORNADO OR TWO -- PARTICULARLY OVER THE ERN CAROLINAS...BUT
   OTHERWISE A MAINLY DIURNAL THREAT FOR HAIL AND/OR LOCALLY-DAMAGING
   WINDS IS EXPECTED INTO THE EVENING HOURS.
   
   ...ERN MN/NWRN WI...
   MARGINAL INSTABILITY HAS EVOLVED ACROSS PARTS OF MN/WI THIS
   AFTERNOON...WITH DAYTIME HEATING OF MODESTLY-MOIST AIRMASS BENEATH
   MID-LEVEL COLD POOL.  A FEW STRONGER CELLS -- CAPABLE OF PRODUCING
   MARGINAL HAIL -- WILL BE POSSIBLE ACROSS PARTS OF ERN MN INTO NWRN
   WI THIS AFTERNOON...WITHIN LARGER AREA OF CONVECTION E/SE OF THE
   CIRCULATION CENTER ALOFT.
   
   ..GOSS.. 05/05/2009
   
   .PREV DISCUSSION... /ISSUED 1122 AM CDT TUE MAY 05 2009/
   
   ...SRN PLAINS...
   PRIMARY CHALLENGE WILL BE TIMING OF INITIATION OF SURFACE BASED
   SEVERE THUNDERSTORMS VICINITY OF THE E/W FRONTAL ZONE THAT STRETCHES
   FROM NRN LA ACROSS NRN TX TO ERN NM.  ONGOING OK STORMS  IN RESPONSE
   TO ASCENT ON NOSE OF 30-40KT LLJ AND ADVECTION OF ELEVATED
   MOISTURE/INSTABILITY. THESE SHOULD REMAIN PRIMARILY HAIL PRODUCERS
   DUE TO THEIR ELEVATED NATURE THRU MID AFTERNOON.
   
   UPSTREAM S/WV TROUGH CENTRAL ROCKIES WILL SPREAD INCREASING ASCENT
   AND SOME MID LEVEL COOLING WHICH COMBINED WITH THE WARM/MOIST
   ADVECTION ACROSS THE FRONTAL ZONE WILL PROVIDE A FERTILE ENVIRONMENT
   FOR SUPERCELL SEVERE THUNDERSTORM DEVELOPMENT LATER THIS AFTERNOON
   AND EVENING.  WITH EXTENSIVE LOW CLOUDINESS WITH THE GULF MOISTURE
   AND HIGH LEVEL CLOUDINESS SPREADING EWD AHEAD OF THE APPROACHING
   TROUGH...ALONG WITH INCONSISTENT MODEL SOLUTIONS...THE PRIMARY
   UNCERTAINTY IS WITH THE TIMING OF THE MOST INTENSE SURFACE/NEAR
   SURFACE BASED INITIATION.  THE DRY LINE WILL MIX EWD TO WCENTRAL TX
   S OF E/W FRONTAL ZONE PROVIDING POTENTIAL FOR INITIATION BY LATER
   THIS AFTERNOON WITH THE FRONTAL INTERSECTION. WITH MLCAPES CLIMBING
   TO AOA 3000 J/KG IN THE WARM SECTOR BY MID AFTERNOON E OF DRY
   LINE...ANY NEAR SURFACE BASED STORM WOULD QUICKLY BECOME SEVERE WITH
   POTENTIAL FOR VERY LARGE HAIL.
   
   AS LOW LEVEL JET INCREASES BY THIS EVENING SEVERE THUNDERSTORMS
   INCLUDING SUPERCELLS WILL BECOME MORE COMMON EWD ALONG AND S OF RED
   RIVER VALLEY VICINITY OF FRONTAL CONVERGENCE.  IN ADDITION TO VERY
   LARGE HAIL...VEERING SHEAR PROFILES WILL BE CONDUCIVE TO VERY LARGE
   HODOGRAPHS AND TORNADO POTENTIAL.  OVERNIGHT A SEVERE MCS SHOULD
   EVOLVE AND TRACK S OF E ACROSS NRN TX POSSIBLY INTO NRN LA BY 12Z
   WED. WIND DAMAGE POTENTIAL WOULD INCREASE AS THE MCS DEVELOPS DURING
   THE EVENING.
   
   ...ERN CAROLINAS...
   MOIST/UNSTABLE AND A WEAKLY CAPPED AIR MASS REMAINS ACROSS AREA TO E
   OF SRN APPALACHIANS AS A S/WV TROUGH PASSES BY TO THE N.
   THUNDERSTORMS ARE ALREADY INCREASING ERN CAROLINAS THIS AM WITHIN AN
   UNCAPPED ENVIRONMENT.  WITH 30-40KT OF SHEAR AND MLCAPES AOA 2000
   J/KG...STRONG/SEVERE STORMS WHICH HAVE DEVELOPED ERN CAROLINAS WILL
   INCREASE IN INTENSITY AS THEY MOVE TOWARD THE COAST...WITH POSSIBLE
   ENHANCEMENT OF CONVERGENCE WITH THE SEA BREEZE FRONT.  AFTERNOON
   HEATING SHOULD SUPPORT REDEVELOPMENT OF STORMS AGAIN ERN CAROLINAS. 
   STORMS WILL EVOLVE INTO SHORT LINE SEGMENTS/BOWS GIVEN THE AVAILABLE
   SHEAR WITH BOTH LARGE HAIL AND WIND DAMAGE THE PRIMARY THREAT.
   
   ...GULF COAST STATES...
   THE MORE DIFFUSE E/W STATIONARY FRONTAL ZONE FROM NRN GA TO CENTRAL
   MS WILL BE A FOCUS FOR PRIMARILY A DIURNAL LOWER END SEVERE
   POTENTIAL TODAY.  WITH SURFACE TEMPS INTO THE 80S AND DEWPOINTS NEAR
   70F ALONG AND S OF FRONT...MLCAPES AGAIN WILL BE QUITE UNSTABLE
   RANGING UPWARDS TO 3000 J/KG WHERE HEATING IS STRONGEST. GENERALLY
   30KT OR LESS OF DEEP LAYER SHEAR SUGGESTS MOST STORMS WILL BE
   MULTI-CELLULAR WITH A LARGE HAIL AND ISOLATED DAMAGING WIND THREAT
   FROM MID AFTERNOON UNTIL LATER THIS EVENING WHEN BOUNDARY LAYER
   STABILIZES.
   
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