ZCZC SPCSWOD48 ALL ACUS48 KWNS 140856 SPC AC 140856 DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0356 AM CDT SUN JUL 14 2013 VALID 171200Z - 221200Z ...DISCUSSION... MULTI-DAY SEVERE EVENT POSSIBLE D5 /THU JUL 18/ THROUGH D7 /SUN JUL 20/ MEDIUM RANGE GUIDANCE FROM THE GFS...ECMWF AND CMC GLOBAL MODELING SYSTEMS HAS BEEN CONSISTENT WITH THE LARGE SCALE PATTERN EVOLUTION DURING THE D4-8 PERIOD SHOWING DEVELOPMENT OF BROAD LONG WAVE TROUGH MOVING ACROSS SERN CANADA...THE GREAT LAKES AND NERN STATES. AS THIS OCCURS A SURFACE LOW...INITIALLY OVER THE NRN PLAINS...WILL MOVE ENEWD ACROSS THE NRN GREAT LAKES AND SERN CANADA WHILE A TRAILING COLD FRONT EXTENDING SWWD FROM THE LOW ADVANCES SEWD ACROSS GREAT LAKES AND NERN STATES. ALTHOUGH THE ECMWF DETERMINISTIC RUNS AND ENSEMBLE SYSTEMS HAVE EXHIBITED MORE RUN-TO-RUN CONTINUITY THAN THE GFS IN THE HANDLING OF THE SHORT WAVE FEATURES AND ASSOCIATED WIND FIELDS ASSOCIATED WITH THE LONG WAVE TROUGH...A SIMILAR LARGE SCALE SIGNAL FROM MULTIPLE MODELING SYSTEMS SUGGESTS PATTERN PREDICTABILITY IS RELATIVELY HIGH DURING THIS PERIOD IN THE REGION OF INTEREST. A VERY MOIST AND UNSTABLE AIR MASS IS LIKELY TO BE PRESENT OVER THE NRN PLAINS/UPPER MS VALLEY AND INTO THE NERN STATES ON D4-5 IN ADVANCE OF THE SURFACE LOW AND COLD FRONT. THIS WILL INCREASE THE POTENTIAL FOR WIDESPREAD DAMAGING WIND GUSTS AND OCCASIONAL HAIL TO OCCUR WITH SEVERE STORMS ALONG AND AHEAD OF THE COLD FRONT. ALTHOUGH PRIMARY THREAT AREAS MAY BE MODULATED BY EFFECTS OF PRIOR CONVECTION/OUTFLOW BOUNDARIES...OVERALL SYNOPTIC SCALE FORCING APPEARS SUFFICIENT TO DELINEATE REGIONS OF ENHANCED SEVERE POTENTIAL DURING THIS PERIOD. D5 /THU JUL 18/...SEVERE STORM POTENTIAL IS EXPECTED TO INCREASE BY LATE AFTERNOON/EVENING OVER THE UPPER MS VALLEY ALONG/NORTH OF A WARM FRONT...WITH SEVERE STORMS POSSIBLY SPREADING EWD DURING THE OVERNIGHT HOURS TOWARD THE GREAT LAKES. THIS WILL OCCUR AS THE SURFACE LOW MOVES EWD AND THE LOW LEVEL JET VEERS...STRENGTHENS AND BECOMES COUPLED WITH A STRONG WNWLY MID/UPPER LEVEL JET POSITIONED IMMEDIATELY TO ITS NORTH. D6 /FRI JUL 19/...THE ELONGATED COUPLED LOW/MID LEVEL JET STRUCTURE IS EXPECTED TO PROGRESS EWD ACROSS THE GREAT LAKES AND INTO THE NERN STATES AS THE SURFACE LOW MOVES ACROSS SRN CANADA...AND THE COLD FRONT MOVES SEWD ACROSS THE GREAT LAKES. SEVERE STORM POTENTIAL IS EXPECTED TO CONTINUE EWD/ESEWD ALONG AND AHEAD OF THE COLD FRONT FROM THE GREAT LAKES INTO NRN PARTS OF THE NERN STATES. D7 /SAT JUL 20/...THE COLD FRONT AND STRONGER WINDS ALOFT WILL MOVE ACROSS THE REMAINDER OF THE NERN STATES AND NRN MIDDLE ATLANTIC REGION MAINTAINING A SEVERE THREAT OVER THIS AREA. ..WEISS.. 07/14/2013 CLICK TO GET WUUS48 PTSD48 PRODUCT