The SPC is forecasting ...significant severe thunderstorms expected over parts of the central and southern high plains this afternoon and tonight....   Please read the latest public statement about this event.

   SPC AC 311229
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0729 AM CDT THU MAY 31 2007
   
   VALID 311300Z - 011200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS LARGE PART OF WESTERN AND
   CENTRAL KS...NWRN OK...NRN TX PANHANDLE. AND A SMALL PART OF
   SOUTHEAST CO AND SCENTRAL NEB....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
   FROM NM AND WEST TX NEWD TO SERN SD AND SWRN MN...
   
   ...SYNOPSIS...
   STACK LOW VICINITY BORDER OF WRN DAKOTAS CONTINUES TO SPIN SLOWLY
   WWD AS LARGE SCALE FLOW OVER CONUS SHOWS LITTLE CHANGE THRU THE
   PERIOD.  40-50KT MID LVL WLYS S OF LOW WILL DEVELOP LEE TROUGH
   CENTRAL HIGH PLAINS AND AID IN RETURN OF THE VERY MOIST/UNSTABLE 
   AIR MASS INITIALLY SRN PLAINS.
   
   CURRENTLY 10-15KT SELY FLOW CENTRAL/SRN HIGH PLAINS WILL GRADUALLY
   INCREASE THRU THE AFTERNOON IN RESPONSE TO THE LEE TROUGHING. THIS
   EVENING THE LOW LEVEL JET KICKS IN WITH 40KT SLY FLOW RAPIDLY
   SPREADING THE MOISTURE/INSTABILITY NWD ACROSS MUCH OF CENTRAL
   PLAINS.
   
   ...CENTRAL AND SRN PLAINS...
   THE INITIALLY FLAT SURFACE PRESSURE PATTERN ACROSS PLAINS WILL
   EVOLVE DURING THE DAY IN RESPONSE TO LEE TROUGH AND SURFACE HEATING
   TO SUPPORT WIDESPREAD SEVERE THUNDERSTORMS BY LATE IN THE DAY. 
   WHILE LOW LEVEL MOISTURE ADVECTS N AND W TOWARD HIGHER ELEVATIONS
   FROM ERN NM BORDER NWD INTO FAR ERN CO...CAPPING WILL INHIBIT
   SURFACE INITIATION UNTIL LATE AFTERNOON FURTHER E OVER HIGH PLAINS.
   
   INITIAL THUNDERSTORM DEVELOPMENT  EXPECTED TO OCCUR OVER SWRN NEB
   AREA WHERE CAP IS WEAKEST... WITHIN MODERATELY UNSTABLE ENVIRONMENT
   WITH MLCAPES OF 1000 J/KG. GIVEN 40-50KT OF DEEP LAYER SHEAR
   ENVIRONMENT WILL BE SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL
   AND POSSIBLE TORNADOES.
   
   BY MID/LATE AFTERNOON THUNDERSTORMS WILL FORM OFF HIGHER TERRAIN
   ALONG NERN NM/TX BORDER INTO SERN CO WHERE LAPSE RATES IN EXCESS OF
   8C/KM AND MLCAPES ABOVE 1000 J/KG WILL BE IN PLACE.  STORMS WILL
   THEN INCREASE IN BOTH NUMBER AND INTENSITY AS THEY MOVE EWD INTO THE
   ADJACENT HIGH PLAINS WHERE A RAPIDLY DESTABILIZING AIR MASS WITH
   MLCAPES IN EXCESS OF 2000 J/KG WILL BE COMMON BY 00Z.  EVENTUALLY
   THE SEVERE STORMS ARE EXPECTED TO EVOLVE INTO ONE OR MORE MCS/S.
   PRIOR TO MCS DEVELOPMENT ...SUPERCELLS ARE EXPECTED TO BE PRIMARY
   CONCERN WITH VERY LARGE HAIL AND POSSIBLY TORNADOES.  ONCE STORMS
   EVOLVE INTO AN MCS/S ORGANIZED DAMAGING WINDS WILL BECOME PRIMARY
   THREAT.
   
   THE WRF NMM DEVELOPS A STRONG SQUALL LINE SIGNAL INTO WRN KS SWD
   INTO TX PANHANDLE THIS EVENING. AS THE STRONG LOW LEVEL JET SPREADS
   THE VERY MOIST/UNSTABLE AIR NWD THRU OK/KS THE POTENTIAL FOR
   SIGNIFICANT DAMAGING WINDS WILL SPREAD RAPIDLY EWD ACROSS CENTRAL KS
   AND WRN OK.
   
   THE EWD EXTENT OF THE GREATER SEVERE THREAT IS SOMEWHAT
   UNCERTAIN...BUT WITH THE IMPRESSIVE MOISTURE/INSTABILITY RETURN
   AFTER 00Z...THE COVERAGE AND INTENSITY OF THE EXPECTED WIND DAMAGE
   HAS BEEN INCREASED.
   
   ...NORTHEAST...
   INITIALLY QUASI-STATIONARY BACK DOOR FRONT IS FORECAST TO EXTEND
   FROM NERN NY TO SRN NEW ENGLAND. WARM SECTOR AIR MASS ALONG AND TO
   THE SW OF THIS BOUNDARY WILL BECOME MODERATELY UNSTABLE /MLCAPE TO
   AROUND 1000 J PER KG/ WITH DAYTIME HEATING. LIFT/FORCING ALONG THE
   BOUNDARY COULD PROVIDE A FOCUS FOR STORM DEVELOPMENT WITH STRONGER
   NWLY FLOW ALOFT PROVIDING ADEQUATE SHEAR FOR A SUPERCELL OR TWO. A
   COUPLE HAIL REPORTS ARE POSSIBLE BUT SOMEWHAT ILL-DEFINED LARGER
   SCALE FORCING FOR LIFT ALONG THE FRONTAL ZONE CURRENTLY PRECLUDES
   HIGH SEVERE PROBABILITIES.
   
   PULSE STORMS ARE FORECAST SWWD ALONG THE APPALACHIANS WITHIN/BENEATH
   LARGE SCALE UPPER RIDGE. GIVEN WEAK FLOW AND DIURNAL FORCING MUCH OF
   THIS ACTIVITY SHOULD WEAKEN BY EVENING WITH ONLY AN ISOLATED CHANCE
   FOR A FEW DAMAGING WIND GUSTS OR SMALL HAIL.
   
   ..HALES/GUYER.. 05/31/2007
   
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