Day 4-8 Convective Outlook

ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 070857
   SPC AC 070857
  
   DAY 4-8 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0357 AM CDT THU APR 07 2011
  
   VALID 101200Z - 151200Z
  
   ...DISCUSSION...
   07/00Z GFS IS IN AGREEMENT WITH THE LAST THREE RUNS OF THE ECMWF
   SHOWING THE STRONGER FORCING FOR ASCENT WITH THE WRN TROUGH TRACKING
   THE SRN/CENTRAL ROCKIES AND REACHING THE MID SOUTH TO WRN GREAT
   LAKES BY THE END OF DAY 4 /12Z MON APR 11/.  WHILE EACH MODEL
   MAINTAINS THE PROGRESSIVENESS OF THIS SYSTEM ON DAY 5 /MON APR
   11/...THE GFS INDICATES THE TROUGH BECOMES NEGATIVELY TILTED MOVING
   INTO THE NERN STATES.  THE ECMWF DURING THIS SAME PERIOD IS SLOWER
   WITH EWD MOVEMENT WITH A MORE NEUTRAL TO POSITIVELY-TILTED TROUGH.
   THE DIFFERENT SOLUTIONS ATTENDANT TO THIS ERN TROUGH ON DAY 5 RESULT
   IN VARYING MAGNITUDES OF AN UPSTREAM RIDGE OVER THE CENTRAL
   STATES...AND THE SUBSEQUENT EWD MOVEMENT OF A PACIFIC TROUGH FROM
   THE WEST COAST TO MS VALLEY NEXT WEEK.
  
   ...DAY 4 /SUN APR 10/...
   THE POTENTIAL FOR A REGIONAL SEVERE THREAT EXTENDING FROM NRN LA TO
   IA AND EWD THROUGH THE TN/OH VALLEYS AND PART OF THE WRN GREAT LAKES
   FROM SUNDAY AFTERNOON THROUGH SUNDAY NIGHT/EARLY MONDAY MORNING
   REMAINS VERY LIKELY.  CONFIDENCE REMAINS HIGH FOR THIS SEVERE
   WEATHER EVENT WITH THE POTENTIAL FOR DAMAGING WINDS AND TORNADOES AS
   STRONG HEIGHT FALLS SPREAD ACROSS THE DAY 4 OUTLOOK AREA...
   ESPECIALLY DURING THE LATTER HALF OF THE FORECAST PERIOD.
  
   A SURFACE LOW ATTENDANT TO THE PROGRESSIVE MID-UPPER LEVEL TROUGH IS
   EXPECTED TO TRACK FROM WRN KS INTO IA BY LATE SUNDAY AFTERNOON AND
   REACH THE WRN GREAT LAKES BY 12Z MONDAY.  A TRAILING COLD FRONT IS
   EXPECTED TO OVERTAKE THE PLAINS DRY LINE WITH TSTMS DEVELOPING
   INITIALLY FROM ERN OK TO WRN IA.  SLY LOW LEVEL WINDS WILL MAINTAIN
   A MOIST AIR MASS ALREADY IN PLACE AT THE START OF DAY 4 AND SUPPORT
   A MODERATELY UNSTABLE WARM SECTOR.  STRENGTHENING DEEP LAYER WIND
   FIELDS ACROSS THE UNSTABLE AIR MASS WILL PROMOTE BOTH LINE SEGMENTS
   AND SUPERCELLS WITH THE INITIAL ACTIVITY SPREADING TO THE MS VALLEY.
   FOR SUNDAY NIGHT...THE SEVERE WEATHER THREAT SHOULD EVOLVE TO
   PRIMARILY DAMAGING WINDS AS A BROAD SWLY LLJ /50-70 KT/ DEVELOPS
   FROM THE MID SOUTH TO OH VALLEY AND A SQUALL LINE ADVANCES EWD FROM
   THE MS VALLEY.
  
   ...DAY 5 /MON APR 11/...
   GIVEN MODEL DIFFERENCES IN THE TIMING AND ORIENTATION OF THE DAY 4
   TROUGH AS IT MOVES EWD ON DAY 5 AND UNCERTAINTY IN THE DEGREE OF
   DESTABILIZATION WITH EWD EXTENT...A REGIONAL SEVERE WEATHER THREAT
   AREA WILL NOT BE INCLUDED FOR THIS PERIOD.
  
   ...BEYOND DAY 5...
   MODEL UNCERTAINTIES WITH THE TIMING OF A PACIFIC TROUGH REACHING THE
   PLAINS STATES NEXT WEEK PRECLUDES THE INCLUSION OF ANY THREAT AREAS
   FOR DAYS 7-8 /WED APR 13 THROUGH THU APR 14/.
  
   ..PETERS.. 04/07/2011