Posted by JAC on 5/28/2009, 7:52 am, in reply to "Re: Severe weather returns to the CONUS this weekend"

DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0356 AM CDT THU MAY 28 2009 VALID 311200Z - 051200Z ...DISCUSSION... GOOD MODEL AGREEMENT BETWEEN THE GFS AND ECMWF CONTINUES IN GENERAL THIS PERIOD...WITH A WNWLY FLOW PATTERN ALOFT EXPECTED ACROSS THE NRN CONUS ON THE SWRN FRINGE OF THE ERN NOAM TROUGH EARLY IN THE PERIOD. WITH TIME...MODELS FORECAST THAT AN UPPER LOW WILL SHIFT EWD OUT OF THE PACIFIC AND INTO THE WRN CONUS...AND WEAKLY-CYCLONIC FLOW TO PREVAIL OVER THE N CENTRAL AND ERN CONUS ON SRN FRINGES OF PERSISTENT CENTRAL AND ERN CANADA TROUGHING. DAY 4 /SUN. MAY 31/...A COLD FRONT IS FORECAST TO SHIFT ACROSS THE MID MO/UPPER MS VALLEY REGION...FOCUSING AFTERNOON CONVECTIVE DEVELOPMENT AS THE WARM SECTOR DESTABILIZES FROM NEB ENEWD INTO IA/MN/WI DURING THE AFTERNOON. SHEAR/INSTABILITY COMBINATION SUPPORTIVE OF SEVERE POTENTIAL WARRANTS CONTINUATION OF A THREAT AREA FROM THE MID MO VALLEY EWD INTO THE SRN UPPER GREAT LAKES REGION. DAY 5 /MON. JUN. 1/...THE FRONT SHOULD CONTINUE EWD ACROSS THE GREAT LAKES...BECOMING MORE E-W ORIENTED FROM THE OH VALLEY WWD INTO THE CENTRAL PLAINS. SECONDARY CYCLOGENESIS IS FORECAST ALONG THE WRN FRINGE OF THE FRONT OVER THE CENTRAL/SRN HIGH PLAINS. GIVEN THIS...AN ELONGATED AREA OF HEIGHTENED SEVERE POTENTIAL APPEARS TO EXIST FROM THE CENTRAL HIGH PLAINS -- WITHIN ELY LOW-LEVEL UPSLOPE REGIME N OF THE DEVELOPING LOW -- ENEWD ACROSS THE MID MO VALLEY INTO THE UPPER MIDWEST. AS THE COLD FRONT CONTINUES EWD ACROSS THE NORTHEAST U.S. DAY 6...SOME THREAT SHOULD EXIST OVER THE NORTHEAST...THOUGH SOME UNCERTAINTY WITH DEGREE OF DESTABILIZATION PRECLUDES THE INITIATION OF A THREAT AREA ATTM. MEANWHILE...THE FRONT SHOULD SAG SWD ACROSS THE OH VALLEY REGION AND MOVE S OF THE STRONGER FLOW ALOFT...LIMITING SEVERE POTENTIAL WITH STORMS DEVELOPING INVOF THE SAGGING FRONT TO SOME DEGREE. A GREATER THREAT APPEARS POSSIBLE OVER THE CENTRAL AND NRN HIGH PLAINS...WITHIN A CONTINUED UPSLOPE FLOW REGIME...BUT WILL REFRAIN AT THIS TIME FROM INTRODUCING A DAY 6 THREAT AREA. BEYOND DAY 6...INCREASING DIFFERENCES IN THE SURFACE PATTERN BETWEEN THE TWO MODELS OVER THE CENTRAL U.S. -- WHERE GREATEST CONVECTIVE CONCERN EXISTS -- PRECLUDES THE ADDITION OF ANY THREAT AREAS. ..GOSS.. 05/28/2009