SPC AC 191730
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT WED APR 19 2006
   
   VALID 201200Z - 211200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THU INTO EARLY FRI FROM PARTS
   OF W TEXAS THRU THE GULF STATES/SRN APPALACHIANS....
   
   BLOCKING WILL PERSIST IN THE LARGE-SCALE UPPER FLOW PATTERN...BUT
   MODELS SUGGEST HIGH CENTER SOUTH OF JAMES BAY WILL WEAKEN LATER
   TONIGHT INTO THURSDAY...AS DEEP NORTHERN PLAINS CLOSED LOW SLOWLY
   SHIFTS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS IS FORECAST TO
   OCCUR AS AN AMPLIFIED TROUGH CONTINUES TO SLOWLY APPROACH THE
   PACIFIC COAST. NORTHERN AND SOUTHERN STREAM IMPULSES COMPRISING
   THIS FEATURE ARE PROGGED TO REMAIN MOSTLY IN PHASE ACROSS THE
   EASTERN PACIFIC THROUGH THIS PERIOD.  HOWEVER...A CLOSED LOW MAY
   SLOWLY BEGIN TO EVOLVE IN THE SOUTHERN STREAM...OFF THE SOUTHERN
   CALIFORNIA COAST...AS NORTHERN SYSTEM APPROACHES THE PACIFIC
   NORTHWEST COAST BY 12Z FRIDAY. 
   
   PERHAPS MORE UNCERTAINTY EXISTS CONCERNING THE PROGRESSIVENESS OF
   IMPULSES IN THE SOUTHERN BRANCH DOWNSTREAM...AROUND SOUTHERN
   PERIPHERY OF NORTH CENTRAL U.S. CLOSED LOW.  MOST SIGNIFICANT OF
   THESE FEATURES IS NOW MIGRATING ACROSS THE SOUTHERN PLATEAU...AND
   GENERALLY PROGGED TO CONTINUE EAST OF THE SOUTHERN ROCKIES EARLY
   THURSDAY...INTO THE SOUTHERN PLAINS RED RIVER VALLEY BY THE END OF
   THE PERIOD.  THIS WILL BE PRECEDED BY A MORE SUBTLE SHORT
   WAVE...WHICH MAY ALREADY BE SUPPORTING CONSIDERABLE CONVECTIVE
   DEVELOPMENT FROM PARTS OF TEXAS INTO THE LOWER MISSISSIPPI VALLEY AT
   12Z THURSDAY.
   
   ...OHIO/TENNESSEE VALLEYS INTO SOUTHEAST STATES...
   SOME EASTWARD PROGRESSION OF WEAKENING SURFACE COLD FRONT WILL OCCUR
   THROUGH THE LOWER OHIO VALLEY...TOWARD THE SOUTHERN APPALACHIANS
   THURSDAY...WITH LOW-LEVEL COOLING/DRYING ALSO OCCURRING TO THE LEE
   OF THE SOUTHERN APPALACHIANS.  HOWEVER...TO THE SOUTH AND WEST OF
   THESE BOUNDARIES...BOUNDARY LAYER IS EXPECTED TO REMAIN MOIST...WITH
   MID 60S+ DEW POINTS.  DESPITE POSSIBILITY OF CONSIDERABLE CLOUD
   COVER...INSOLATION IS EXPECTED TO BE SUFFICIENT TO SUPPORT MIXED
   LAYER CAPE OF 1000 TO 2000 J/KG BY PEAK HEATING.
   
   DESTABILIZATION LIKELY WILL BE SUPPORTIVE OF VIGOROUS CONVECTIVE
   DEVELOPMENT...AIDED BY FORCING ASSOCIATED WITH LEAD SOUTHERN BRANCH
   IMPULSE...PROGGED EAST OF THE LOWER MISSISSIPPI VALLEY INTO THE
   SOUTHERN APPALACHIANS BY EARLY THURSDAY EVENING.  LOW-LEVEL WIND
   FIELDS ARE EXPECTED TO BE WEAK...BUT DEEP LAYER SHEAR BENEATH WEAK
   TO MODERATE MID/UPPER FLOW MAY BE FAVORABLE FOR AT LEAST BRIEF
   UPDRAFT ROTATION.  THIS WILL ENHANCE RISK FOR LARGE HAIL/DAMAGING
   WIND GUSTS IN STRONGER STORMS...BEFORE ACTIVITY WEAKENS WITH LOSS OF
   SURFACE HEATING.
   
   ...TEXAS...
   LAPSE RATES WILL BECOME QUITE STEEP ABOVE MOIST BOUNDARY LAYER EAST
   OF DRY LINE...AND SOUTH OF SURFACE FRONTAL ZONE...ACROSS PARTS OF
   WESTERN AND CENTRAL TEXAS.  LOCATION OF TRIPLE POINT LOW BY PEAK
   HEATING IS STILL A BIT UNCERTAIN...BUT THIS FEATURE IS EXPECTED TO
   PROVIDE THE FOCUS FOR PRIMARY CONVECTIVE DEVELOPMENT AS FORCING
   INCREASES WITH APPROACH OF VIGOROUS SOUTHERN BRANCH TROUGH LATE
   THURSDAY AFTERNOON/EVENING.
   
   MIXED LAYER CAPE IN EXCESS OF 2000 J/KG WILL SUPPORT INTENSE
   UPDRAFTS AS 50+ KT WESTERLY 500 MB JET STREAK CONTRIBUTES TO
   FAVORABLE SHEAR PROFILES FOR SUPERCELLS.  THOUGH LOW-LEVEL WIND
   FIELDS WILL BE SOMEWHAT MODERATE IN STRENGTH...VEERING WITH HEIGHT 
   MAY AUGMENT LOW-LEVEL HODOGRAPHS ENOUGH FOR RISK OF TORNADOES... IN
   ADDITION TO VERY LARGE HAIL AND DAMAGING WIND GUSTS.  ACTIVITY MAY
   EVENTUALLY CONSOLIDATE INTO A SEVERE MESOSCALE CONVECTIVE SYSTEM
   BEFORE WEAKENING ACROSS PARTS OF NORTHERN/EASTERN TEXAS LATE
   THURSDAY NIGHT.
   
   ..KERR.. 04/19/2006
   
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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z