Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 130554
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1254 AM CDT SAT JUN 13 2009
   
   VALID 131200Z - 141200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN AND EVE ACROSS PARTS
   OF THE CNTRL/SRN PLAINS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE
   CNTRL/ERN GULF STATES...
   
   ...SYNOPSIS...
   MODELS INDICATE ONLY SUBTLE...SLOW CHANGES WITHIN THE PREVAILING
   SPLIT UPPER FLOW REGIME THROUGH THIS FORECAST PERIOD.  HIGH MOISTURE
   CONTENT AIR SUPPORTIVE OF MODERATE TO STRONG INSTABILITY IS EXPECTED
   TO REMAIN MOSTLY CONFINED TO AREAS ALONG AND SOUTH OF THE SEASONABLY
   STRONG SOUTHERN BRANCH OF THE SPLIT FLOW...TOPPING THE CREST OF A
   BROAD SUBTROPICAL RIDGE.  THIS RIDGE APPEARS LIKELY TO REMAIN
   CENTERED OVER THE LOWER RIO GRANDE VALLEY/NORTHEAST MEXICO
   REGION...BUT A NORTHEASTWARD EXPANSION IS NOW UNDERWAY THROUGH THE
   CENTRAL/SOUTHERN PLAINS AND LOWER HALF OF THE MISSISSIPPI VALLEY.
   
   A SIGNIFICANT SHORT WAVE IMPULSE IS BEGINNING TO LIFT OUT OF THE
   UPSTREAM SOUTHERN BRANCH...INTO/THROUGH SOUTHERN CALIFORNIA AND THE
   LOWER COLORADO VALLEY...BEFORE CONTINUING THROUGH THE CREST OF THE
   RIDGE OVER THE CENTRAL ROCKIES/HIGH PLAINS LATER TODAY/TONIGHT.  IN
   RESPONSE TO THIS FEATURE...AND THE SLOW EASTWARD PROGRESSION OF THE
   DOWNSTREAM NORTHERN BRANCH TROUGH ACROSS THE GREAT LAKES
   REGION...LAPSE RATES ARE PROGGED TO STEEPEN EAST OF THE ROCKIES INTO
   THE HIGH PLAINS.  AT THE SAME TIME...A RETURN FLOW OF MOISTURE IS
   EXPECTED TO STRENGTHEN THROUGH MUCH OF THE PLAINS.
   
   ...CENTRAL HIGH PLAINS INTO THE SOUTHERN PLAINS...
   VEERING WINDS WITH HEIGHT...FROM SOUTHEASTERLY AT THE SURFACE TO
   30-40+ KT WESTERLY AT 500 MB...WILL CONTRIBUTE TO FAVORABLE SHEAR
   FOR SUPERCELLS ACROSS MUCH OF THE REGION AS DESTABILIZATION OCCURS
   TODAY.  OROGRAPHIC FORCING WILL CONTRIBUTE TO THE INITIATION OF
   STORMS ACROSS THE FRONT RANGE...WHILE LARGE-SCALE FORCING ASSOCIATED
   WITH THE APPROACHING SHORT WAVE IMPULSE SUPPORTS  CONVECTIVE
   DEVELOPMENT ACROSS AND TO THE LEE OF THE HIGHER TERRAIN.
   
   STRONG HEATING ALONG AND SOUTH OF A REMNANT SURFACE FRONT ACROSS THE
   TEXAS PANHANDLE AND NORTHWEST TEXAS LIKELY WILL FOCUS THE MOST
   PRONOUNCED DESTABILIZATION...WHICH MAY BECOME STRONG TO EXTREME AS
   CHARACTERIZED BY MIXED LAYER CAPE OF 3000-4000 J/KG.  GUIDANCE IS
   SUGGESTIVE THAT INTERACTING UPPER JET STREAKS COULD FOCUS A
   DIVERGENT UPPER FLOW FIELD ALONG THIS BOUNDARY BY OR SHORTLY AFTER
   THE PEAK HEATING HOURS...WHICH COULD PROMOTE THE CONSOLIDATION OF
   STORMS INTO A GROWING CONVECTIVE CLUSTER THROUGH EARLY EVENING.  IN
   ADDITION TO LARGE HAIL...A FEW DAMAGING DOWNBURSTS ARE POSSIBLE.  AS
   A MODEST SOUTHERLY LOW-LEVEL JET DEVELOPS DURING THE LATE
   EVENING...A WINDOW OF OPPORTUNITY APPEARS TO EXIST FOR INCREASING
   ORGANIZATION AND A STRENGTHENING SURFACE COLD POOL ACROSS WESTERN
   OKLAHOMA AND ADJACENT PORTIONS OF THE RED RIVER VALLEY.
   
   ...CENTRAL/EASTERN GULF STATES...
   A MID-LEVEL CONVECTIVELY GENERATED VORTEX APPEARS LIKELY TO
   GRADUALLY SHIFT ACROSS GEORGIA COASTAL AREAS EARLY TODAY...WITH AN
   ASSOCIATED SURFACE BOUNDARY STALLING ACROSS SOUTHERN GEORGIA/
   NORTHERN FLORIDA THROUGH THE CENTRAL GULF COAST STATES.  IT APPEARS
   THAT A MOIST ENVIRONMENT ALONG THIS BOUNDARY WILL BECOME MODERATELY
   UNSTABLE...AS LARGE-SCALE ASCENT INCREASES AHEAD OF ANOTHER WEAK
   IMPULSE ROUNDING THE NORTHEASTERN PERIPHERY OF THE SUBTROPICAL
   RIDGE.  THIS APPEARS TO BE SUPPORTING ONGOING STORMS ACROSS THE
   OZARK PLATEAU...AND COULD REACH CENTRAL MISSISSIPPI AND ALABAMA AS
   THE BOUNDARY LAYER BEGINS TO DESTABILIZE LATER THIS MORNING. 
   BENEATH NORTHWESTERLY 500 MB FLOW ON THE ORDER OF 30-40 KTS...DEEP
   LAYER SHEAR WILL BE SUFFICIENT FOR MID-LEVEL UPDRAFT ROTATION. 
   AND...POTENTIAL EXISTS FOR THE EVOLUTION OF ONE OR MORE SMALL STORM
   CLUSTERS CAPABLE OF PRODUCING DAMAGING WINDS AND HAIL INTO/THROUGH
   THE AFTERNOON HOURS.
   
   ..KERR/GRAMS.. 06/13/2009
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z