SPC AC 040531
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1231 AM CDT SAT JUL 04 2009
   
   VALID 051200Z - 061200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
   THE CAROLINAS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL HIGH PLAINS...
   
   ...SYNOPSIS...
   UPPER FLOW PATTERN IS FORECAST TO AMPLIFY ON SUNDAY AS A JET STREAK
   DIGS SEWD ACROSS THE UPPER MS VALLEY AND SRN GREAT LAKES...RESULTING
   IN THE DEVELOPMENT OF ANOTHER LOW OVER SRN ONTARIO...AND MAINTENANCE
   OF THE LONG WAVE TROUGH OVER THE ERN STATES.  IN THE WEST...THE
   RIDGE IS FORECAST TO BUILD FROM THE SRN PLATEAU INTO THE CANADIAN
   ROCKIES AS AN UPSTREAM LOW OVER THE ERN PACIFIC MOVES EWD...REACHING
   THE PACIFIC NW COAST BY THE END OF THE PERIOD.  A BROAD REGION OF
   NWLY/WLY FLOW ALOFT WILL AFFECT MUCH OF THE US EAST OF THE
   CONTINENTAL DIVIDE.
   
   AT THE SURFACE...A LOW INITIALLY OVER ERN KY WILL MOVE EWD ALONG A
   QUASI-STATIONARY FRONT EXTENDING ACROSS SRN VA DURING THE DAY AND
   CONTINUE EWD INTO THE ATLANTIC SUNDAY NIGHT.  A COLD FRONT TRAILING
   WSWWD FROM THE LOW WILL SLOWLY MOVE SWD INTO THE SERN STATES...LOWER
   MS VALLEY...AND CENTRAL TX.  
   
   ...LOWER MS VALLEY INTO THE CAROLINAS...
   SCATTERED CONVECTION IS EXPECTED TO BE ONGOING EARLY IN THE PERIOD
   FROM PARTS OF VA WSWWD ACROSS THE CENTRAL APPALACHIANS AND TN VALLEY
   INTO THE SRN PLAINS ALONG/AHEAD OF THE AFOREMENTIONED FRONTAL
   BOUNDARY.  EXTENSIVE CLOUDS/PRECIPITATION NEAR THE FRONT IS EXPECTED
   TO LIMIT DIURNAL HEATING AND SUBSEQUENT DESTABILIZATION...ALTHOUGH
   SOME BREAKS IN CLOUD COVER MAY PERMIT LOCALIZED AREAS OF STRONGER
   HEATING.  MORE WIDESPREAD HEATING WILL BE POSSIBLE ALONG AND SOUTH
   OF THE SRN EDGE OF THE AGGREGATE CLOUD SHIELD...WHERE A DIFFERENTIAL
   HEATING BOUNDARY MAY BECOME ESTABLISHED THAT WILL ENHANCE INITIATION
   OF NEW CONVECTION.
   
   DESPITE RELATIVELY WARM MID LEVEL TEMPERATURES...SURFACE DEW POINTS
   IN THE UPPER 60S/LOWER 70S COUPLED WITH TEMPERATURES WARMING ABOVE
   90 WILL RESULT IN MLCAPE OF 1000-2000 J/KG.  THUNDERSTORMS ARE
   EXPECTED TO INCREASE IN COVERAGE BY EARLY AFTERNOON AS HEATING AND
   LOW LEVEL CONVERGENCE WEAKEN THE CAP.  WNWLY/WLY WINDS OF 30-35 KT
   ABOVE 2-3 KM AGL WILL RESULT IN SUFFICIENT VERTICAL SHEAR TO AID IN
   STORM ORGANIZATION...INCLUDING DEVELOPMENT OF SMALL SCALE BOW
   STRUCTURES.  FORECAST SOUNDINGS SHOW LOW-LEVEL INVERTED-V PROFILES
   AND MODERATE DCAPE VALUES SUGGESTING POTENTIAL FOR STRONGER STORMS
   TO PRODUCE DAMAGING WIND GUSTS...WITH A LESSER THREAT FOR LARGE
   HAIL...PRIMARILY DURING THE AFTERNOON AND EARLY EVENING HOURS.
   
   ...CENTRAL HIGH PLAINS...
   WEAK UPSLOPE FLOW IS EXPECTED TO DEVELOP DURING THE AFTERNOON WITH
   SURFACE DEW POINTS REMAINING IN THE 50S ACROSS THE AREA.  ALTHOUGH
   THE STEEPER MID LEVEL LAPSE RATES ARE FORECAST TO REMAIN PRIMARILY
   OVER THE HIGHER TERRAIN...STRONG DIURNAL HEATING WILL CONTRIBUTE TO
   AN UNSTABLE ENVIRONMENT WITH MLCAPE OF 1000-1500 J/KG. 
   THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE ERN SLOPES OF THE
   ROCKIES AND ADJACENT HIGH PLAINS DURING THE MID/LATE AFTERNOON AND
   SPREAD SEWD WITHIN 25-35 KT WNWLY MID LEVEL FLOW.  FORECAST
   SOUNDINGS SHOW WINDS VEERING AND INCREASING WITH HEIGHT WITH
   SUFFICIENT SHEAR TO SUPPORT ORGANIZED STORMS...INCLUDING A FEW
   SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND GUSTS. 
   THE SEVERE THREAT IS LIKELY TO DIMINISH SEVERAL HOURS AFTER SUNSET.
   
   ...NRN/CNTRL TX INTO ERN NM...
   STRONG STORMS ARE EXPECTED TO MOVE SEWD/SWD ACROSS PARTS OF NRN TX
   DURING THE MORNING IN ADVANCE OF THE COLD FRONT.  THERE IS POTENTIAL
   FOR CONVECTION TO INTENSIFY DURING THE AFTERNOON AS STRONG
   HEATING/DESTABILIZATION OCCURS INTO CNTRL/SWRN TX.  ADDITIONAL
   STRONG STORMS ARE EXPECTED TO DEVELOP OVER PARTS OF ERN NM DURING
   THE AFTERNOON...MOVING SEWD INTO PARTS OF NWRN TX BY EVENING. 
   ISOLATED SEVERE STORMS WILL BE POSSIBLE BUT OVERALL COVERAGE IS
   EXPECTED TO BE LIMITED BY WEAK FLOW/VERTICAL SHEAR.
   
   ..WEISS.. 07/04/2009
   
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