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.