May 12, 2011 0600 UTC Day 1 Convective Outlook
Updated: Thu May 12 05:48:05 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110512 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110512 1200 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20110512 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20110512 1200 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
   SPC AC 120544
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1244 AM CDT THU MAY 12 2011
   
   VALID 121200Z - 131200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS SOUTHERN/EASTERN
   TEXAS NORTHWARD INTO PARTS OF THE LOWER/MID MISSOURI VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE LOWER
   GREAT LAKES AND UPPER OHIO VALLEY...
   
   ...SYNOPSIS...
   BLOCKING WILL PERSIST WITHIN THE LARGE-SCALE PATTERN IMPACTING MUCH
   OF NORTH AMERICA THROUGH THIS FORECAST PERIOD.  AS LARGE CLOSED LOWS
   LINGER OFF BOTH THE PACIFIC AND ATLANTIC COASTS...AN UPPER HIGH
   CENTER APPEARS LIKELY TO BECOME MORE PROMINENT OVER THE CENTRAL
   CANADIAN PROVINCES.  TO THE SOUTH/EAST OF THE HIGH... ANOTHER
   SIGNIFICANT CLOSED LOW IS PROGGED TO GRADUALLY WEAKEN AND SLOWLY
   ACCELERATE SOUTHEASTWARD FROM THE CENTRAL HIGH PLAINS... TOWARD THE
   OZARK PLATEAU...AS ANOTHER IMPULSE DIGS TOWARD THE CENTRAL
   CANADIAN/U.S. BORDER AREA.  AS THIS OCCURS...AND ANOTHER SHORT WAVE
   IMPULSE SLOWLY PROGRESSES THROUGH THE CREST OF THE DOWNSTREAM UPPER
   RIDGE...WEAK MID-LEVEL HEIGHT FALLS MAY COMMENCE ACROSS MUCH OF THE
   EAST.
   
   THIS EVOLVING PATTERN IS EXPECTED TO BECOME SUPPORTIVE OF
   CONSIDERABLE THUNDERSTORM ACTIVITY AGAIN TODAY...AS WEAK TO MODERATE
   DESTABILIZATION OCCURS IN THE PRESENCE OF SEASONABLE MOISTURE.  WITH
   THE EXCEPTION OF PORTIONS OF THE EASTERN GULF COAST STATES...THIS IS
   LIKELY TO IMPACT AREAS FROM THE EASTERN PLAINS EASTWARD INTO THE
   APPALACHIANS...AND SOUTHWARD THROUGH THE SOUTH ATLANTIC COAST
   STATES.  THE RISK FOR ORGANIZED SEVERE THUNDERSTORM DEVELOPMENT IS
   BECOMING MORE UNCLEAR...HOWEVER...AS DEEP LAYER FLOW FIELDS AND
   SHEAR ASSOCIATED WITH THE PLAINS CLOSED LOW BECOME INCREASINGLY
   MODEST.
   
   ...SRN/ERN TEXAS NORTHWARD INTO THE MID MISSOURI VALLEY...
   CONVECTIVE OUTFLOW HAS STABILIZED MUCH OF THE SOUTHEASTERN PLAINS
   ...AND DIFLUENT/DIVERGENT UPPER FLOW MAY CONTINUE TO SUPPORT
   CONVECTIVE DEVELOPMENT ALONG THE SOUTHERN FLANK OF THE REMNANT
   BOUNDARY ACROSS PARTS OF SOUTHEAST TEXAS AND LOUISIANA INTO THE
   EARLY PART OF THE FORECAST PERIOD.  ADDITIONAL STORM DEVELOPMENT
   STILL APPEARS POSSIBLE PRIOR TO 12Z THIS MORNING OFF THE HIGHER
   TERRAIN OF MEXICO...AND ALONG THE OUTFLOW BOUNDARY EXTENDING INTO
   THE RIO GRANDE VALLEY SOUTH OF DEL RIO.  THIS LATTER ACTIVITY MAY BE
   SUPPORTED BY FORCING ASSOCIATED WITH AN IMPULSE EMBEDDED WITHIN THE
   SUBTROPICAL JET...WHICH IS EXPECTED TO SPREAD EASTWARD ACROSS
   SOUTHERN TEXAS AND LOWER/MID TEXAS COASTAL AREAS THROUGH EARLY THIS
   AFTERNOON.  AS A MOIST BOUNDARY LAYER...CHARACTERIZED BY SURFACE DEW
   POINTS NEAR 70F...WARMS BENEATH STEEP MID-LEVEL LAPSE RATES...THE
   DEVELOPMENT OF MODERATE TO STRONG MIXED LAYER CAPE APPEARS TO
   PROVIDE AT LEAST SOME POTENTIAL FOR THE EVOLUTION OF AN ORGANIZED
   STORM CLUSTER CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND
   GUSTS.
   
   FARTHER NORTH THROUGH THE PLAINS...AND NORTHEAST THROUGH THE
   MISSISSIPPI VALLEY...THE MAGNITUDE OF THE CONVECTIVE POTENTIAL IS
   MORE UNCLEAR...AND COULD BE COMPLICATED FURTHER BY EARLY DAY CLOUD
   COVER AND CONVECTION.  ALTHOUGH WIND FIELDS ARE EXPECTED TO
   WEAKEN...MID-LEVEL FLOW IN A CYCLONIC BELT ACROSS THE SOUTH CENTRAL
   PLAINS INTO THE OZARK PLATEAU IS EXPECTED TO REMAIN STRONG ENOUGH TO
   CONTRIBUTE TO AT LEAST MARGINALLY SUFFICIENT SHEAR FOR SUPERCELLS
   AND ORGANIZED STORM CLUSTERS.  FAIRLY COLD MID-LEVEL TEMPERATURES
   /-15 TO -18C AT 500 MB/ ON THE PERIPHERY OF THE UPPER LOW WILL
   CONTRIBUTE TO STEEP MID-LEVEL LAPSE RATES ACROSS THIS REGION...AND
   AT LEAST POCKETS OF MODERATE MIXED LAYER CAPE MAY DEVELOP ACROSS
   PORTIONS OF NORTHEAST TEXAS/EASTERN OKLAHOMA AND EASTERN
   KANSAS/WESTERN MISSOURI BY LATE AFTERNOON.  IF THIS OCCURS...ANOTHER
   IMPULSE PIVOTING AROUND THE UPPER LOW PROBABLY WILL CONTRIBUTE TO
   FORCING FOR STORM DEVELOPMENT...WHICH MAY BE CAPABLE OF PRODUCING
   LARGE HAIL AND DAMAGING WIND GUSTS INTO THE EVENING HOURS AS IT
   SPREADS NORTHEASTWARD.
   
   ...LOWER GREAT LAKES UPPER OHIO VALLEY...
   ALTHOUGH DEEP LAYER FLOW AND SHEAR LIKELY WILL REMAIN WEAK THROUGH
   THE PERIOD...GUIDANCE INDICATES THAT A MOIST BOUNDARY LAYER WILL
   BECOME MODERATELY UNSTABLE WITH DAYTIME HEATING.  COUPLED WITH
   FORCING ASSOCIATED WITH THE SHORT WAVE IMPULSE TOPPING THE CREST OF
   THE UPPER RIDGE...THERE APPEARS TO BE POTENTIAL FOR THE DEVELOPMENT
   OF A SIZABLE CONVECTIVE CLUSTER CAPABLE OF GENERATING A SIGNIFICANT
   SURFACE COLD POOL ACCOMPANIED BY POTENTIALLY DAMAGING WIND GUSTS. 
   HIGHEST PROBABILITIES APPEAR TO EXIST ACROSS NORTHERN/EASTERN OHIO
   INTO THE NORTH CENTRAL APPALACHIANS DURING THE 12/21-13/03Z TIME
   FRAME.
   
   ..KERR.. 05/12/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z