
 NWS STORM PREDICTION CENTER NORMAN OK
   0750 AM CDT THU APR 16 2009   
   VALID 161300Z - 171200Z   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
   HIGH PLAINS...   
   ...SYNOPSIS...
   CLOSED UPPER LOW NEARING THE FOUR CORNERS AREA WILL MOVE SLOWLY EAST
   TODAY...AS A DRYLINE/LEE TROUGH WILL PERSIST OVER THE HIGH PLAINS IN
   ADVANCE OF THIS FEATURE. THE DRYLINE WILL MIX EASTWARD ACROSS WEST
   TX DURING THE DAY...AND THEN RETREAT WESTWARD DURING THE EVENING
   BEFORE IT IS OVERTAKEN BY AN OCCLUDING/PACIFIC COLD FRONT.   
   ...CENTRAL/SOUTHERN HIGH PLAINS...
   EARLY MORNING SURFACE ANALYSIS/12Z OBSERVED RAOBS DEPICT A
   WEST-NORTHWESTWARD RETURN OF MODEST BOUNDARY LAYER MOISTURE ACROSS
   TX SINCE LAST EVENING...ALTHOUGH 60+ F SURFACE DEWPOINTS ARE
   CONFINED TO THE TX HILL COUNTRY/SOUTH TX AS OF 13Z. INITIALLY...ON
   THE EASTERN PERIPHERY OF A STRONG ELEVATED MIXED LAYER SAMPLED BY
   12Z REGIONAL RAOBS SUCH AS AMA/MAF/DRT/DDC...THERE IS SOME POTENTIAL
   FOR EARLY DAY TSTMS TO POSE A HAIL RISK ACROSS PORTIONS OF CENTRAL
   TX/HILL COUNTRY OWING TO A LEAD MID LEVEL IMPULSE CROSSING FAR
   NORTHERN MEXICO EARLY THIS MORNING. WITH IMPLIED LIFT/MID LEVEL
   MOISTENING NOTED EARLY THIS MORNING ACROSS THE TX HILL COUNTRY...A
   CONDITIONAL SURFACE BASED SEVERE THREAT COULD EVOLVE WITHIN THIS
   CORRIDOR...ALTHOUGH THE STRENGTH OF THE CAP /PER 12Z DRT RAOB/
   SHOULD LIMIT APPRECIABLE SURFACE BASED DEVELOPMENT.   
   OTHERWISE...A MORE ORGANIZED SEVERE THREAT SHOULD DEVELOP FARTHER
   WEST ACROSS THE CENTRAL/SOUTHERN HIGH PLAINS IN VICINITY OF THE LEE
   TROUGH/DRYLINE LATER THIS AFTERNOON/EVENING. DIABATIC HEATING
   BENEATH STEEP MID LEVEL LAPSE RATES WILL CONTRIBUTE TO
   DESTABILIZATION/WEAKENING CINH ACROSS THE HIGH PLAINS BY
   AFTERNOON...WITH MAINLY 50S F DEWPOINTS SUPPORTING AN AXIS OF MLCAPE
   FROM 1000-1500 J/KG OVER THE TRANSPECOS REGION OF WEST TX TO AROUND
   500 J/KG ACROSS EAST CENTRAL/SOUTHEAST CO. WHILE THE STRONG CAP
   SHOULD LIMIT SURFACE BASED TSTM DEVELOPMENT THROUGH AT LEAST EARLY
   AFTERNOON...GRADUAL LARGE SCALE HEIGHT FALLS/ADVANCING EXIT REGION
   OF UPPER JET AIDED BY LOW LEVEL UPSLOPE TRAJECTORIES/AMPLE
   HEATING...SHOULD LEAD TO A BROAD NNW-SSE CORRIDOR OF SURFACE BASED
   TSTM DEVELOPMENT AROUND MID/LATE AFTERNOON ACROSS THE HIGH
   PLAINS...INITIALLY FROM EASTERN CO/FAR WESTERN KS TO TX
   PANHANDLE/WEST TX.   
   WITH SUFFICIENT INSTABILITY AND 35-50 KT SOUTH-SOUTHWESTERLY MID
   LEVEL FLOW...LOW LEVEL VEERING/40+ KT OF EFFECTIVE SHEAR WILL
   SUPPORT SUPERCELLS. SEVERE HAIL WILL LIKELY BE THE PRIMARY
   THREAT...WITH DAMAGING WINDS POSSIBLE AS WELL VIA DEEP MIXING
   ESPECIALLY ACROSS WEST TX AND/OR EVENTUAL STORM MERGERS LATER THIS
   EVENING. ALTHOUGH A TORNADO OR TWO WILL BE POSSIBLE...MODEST
   BOUNDARY LAYER MOISTURE AND/OR INITIALLY LIMITED HODOGRAPH SIZE WILL
   TEND TO CURB THE THREAT.   
   THUNDERSTORM COVERAGE IS EXPECTED TO INCREASE...AND STORMS WILL
   LIKELY GROW UPSCALE INTO ONE OR MORE QUASI-ORGANIZED MCS/S...LATER
   IN THE EVENING/OVERNIGHT AS THE OCCLUDING/PACIFIC FRONT AND LEADING
   EDGE OF COOLER MID-LEVEL TEMPERATURES/ASCENT ACCOMPANYING THE UPPER
   TROUGH OVERTAKE THE RETREATING DRYLINE. THREAT FOR ISOLATED LARGE
   HAIL/DAMAGING WIND WILL LIKELY CONTINUE INTO THE OVERNIGHT...MAINLY
   ACROSS WEST/NORTHWEST TX AND FAR WESTERN OK.   
   ..GUYER/JEWELL.. 04/16/2009   
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