SPC AC 210813
   
   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0313 AM CDT SAT MAY 21 2005
   
   VALID 231200Z - 241200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
   THE SERN U.S....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL AND SRN
   HIGH PLAINS...
   
   ...SYNOPSIS...
   
   UPPER FLOW PATTERN WILL CONTINUE TO BE CHARACTERIZED BY A BROAD
   UPPER LOW OVER THE ERN U.S. AND A LARGE UPPER RIDGE OVER THE SWRN
   STATES. THE SHORTWAVE TROUGH NOW OVER THE NRN ROCKY MOUNTAIN REGION
   WILL CONTINUE EAST OVER CREST OF SWRN U.S. UPPER RIDGE THEN SE INTO
   THE OH AND TN VALLEYS MONDAY. ASSOCIATED SURFACE FRONT WILL EXTEND
   FROM A LOW OVER THE CNTRL APPALACHIANS SWWD INTO THE SRN HIGH PLAINS
   EARLY MONDAY. BY LATE MONDAY THE ERN PART OF THE FRONT WILL HAVE
   MOVED OFFSHORE WITH TRAILING PORTIONS ALONG THE GULF COAST. WRN
   PORTIONS OF THE FRONT SHOULD STALL OVER THE SRN PLAINS.
   
   ...SERN STATES...
   
   MODERATE INSTABILITY IS EXPECTED WITHIN THE PRE-FRONTAL WARM SECTOR
   ACROSS THE SERN U.S. WHERE SURFACE HEATING CAN BE REALIZED. MLCAPE
   FROM 1500 TO 2000 J/KG WILL BE POSSIBLE MONDAY AFTERNOON. STRONG
   DEEP LAYER NWLY FLOW AND VERTICAL SHEAR WILL EXIST IN ASSOCIATION
   WITH THE AMPLIFYING UPPER TROUGH. STORMS MAY BE ONGOING EARLY MONDAY
   ALONG AND JUST AHEAD OF THE FRONT FROM THE MID ATLANTIC SWWD INTO
   PARTS OF THE CAROLINAS AND TN VALLEY. ACTIVITY IS EXPECTED TO
   INTENSIFY DURING THE DAY AS IT CONTINUES SEWD INTO THE DESTABILIZING
   WARM SECTOR. POTENTIAL WILL EXIST FOR ORGANIZED STORMS INCLUDING
   SUPERCELLS AND BOW ECHOES WITH DAMAGING WIND AND LARGE HAIL THE MAIN
   THREATS.
   
   ...HIGH PLAINS...
   
   MOISTURE WILL BEGIN RETURNING NWD THROUGH THE CNTRL HIGH PLAINS AS
   SURFACE RIDGE SHIFTS EAST AND A LEE TROUGH DEVELOPS IN ITS WAKE. LOW
   LEVEL DEWPOINTS IN THE UPPER 40S TO AROUND 50 WILL BE POSSIBLE AS
   FAR N AS THE HIGH PLAINS OF CO WITH LOWER TO MID 40S FARTHER N INTO
   WY AND ERN MT. SURFACE HEATING AND STEEPENING LAPSE RATES SHOULD
   CONTRIBUTE TO MLCAPE FROM 1500 TO 2000 J/KG OVER THE SRN AND CNTRL
   HIGH PLAINS WITH MORE MARGINAL INSTABILITY FARTHER N. STORMS SHOULD
   DEVELOP OVER THE MOUNTAINS AS OROGRAPHIC FORCING INCREASES IN
   RESPONSE TO SURFACE HEATING. VERTICAL SHEAR WILL SUPPORT SUPERCELLS
   WITH LARGE HAIL LIKELY. HAVE INCLUDED ERN CO AND NE NM IN A SLIGHT
   RISK WHERE STRONGER NWLY FLOW ALOFT SUGGEST STORMS MAY ABLE TO MOVE
   OFF THE MOUNTAINS AND INTO THE HIGH PLAINS. FARTHER N INTO THE NRN
   HIGH PLAINS A SHORTWAVE TROUGH AND ACCOMPANYING COLD FRONT WILL MOVE
   THROUGH ERN MT AND INTO THE WRN DAKOTAS. HOWEVER...LIMITED MOISTURE
   RETURN AND EXPECTED WEAKER INSTABILITY PRECLUDES A SLIGHT RISK AT
   THIS TIME.
   
   ...SRN PLAINS...
   
   THE ATMOSPHERE IS EXPECTED TO BECOME QUITE UNSTABLE OVER PARTS OF
   THE SRN PLAINS IN VICINITY OF STALLED BOUNDARY. HOWEVER...THE
   POTENTIAL FOR A STRONGER CAP AND WEAKER FORCING FOR ASCENT IN THIS
   REGION SUGGEST THUNDERSTORM INITIATION REMAINS UNCERTAIN. GIVEN THE
   CONDITIONAL NATURE OF THE THREAT...WILL ISSUE ONLY LOW SEVERE
   PROBABILITIES AT THIS TIME. AN UPGRADE TO SLIGHT RISK MIGHT BE
   NECESSARY IN LATER OUTLOOKS.
   
   ..DIAL.. 05/21/2005
   
   ...NOTICE...
   THE STATION RELATIVE POINTS IN THIS PRODUCT ARE NOW AVAILABLE
   SEPARATELY UNDER THE WMO HEADINGS WUUS01 PTSDY1...
   WUUS02 PTSDY2...WUUS03 PTSDY3.  THE INCLUSION OF POINTS
   IN THIS DISCUSSION WILL BE DISCONTINUED AFTER THE 2005
   CONVECTIVE SEASON.  A PUBLIC NOTIFICATION STATEMENT (PNS)
   WILL PROVIDE DETAILS ON THE TRANSITION.
   
   CLICK TO GET WUUS03 PTSDY3 PRODUCT

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z