SWOD48
SPC AC 220700
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0200 AM CDT THU SEP 22 2011
VALID 251200Z - 301200Z
...DISCUSSION...
REASONABLE AGREEMENT EXISTS AMONGST MEDIUM RANGE NUMERICAL GUIDANCE
THAT THE LARGE CUT-OFF LOW OVER THE MIDWEST WILL REMAIN A
SEMI-PERMANENT FEATURE ON THE UPPER AIR MAPS INTO NEXT WEEK. LATEST
GFS AND YESTERDAY/S 12Z UKMET...AS WELL AS YESTERDAY/S ECMWF
ENSEMBLE MEAN ALL KEEP THE CUT-OFF LOW CENTERED SOMEWHERE BETWEEN
THE LOWER GREAT LAKES AND OHIO VALLEY THROUGH AT LEAST MONDAY/DAY5.
A STRONG OPEN WAVE FROM THE NERN PAC IS FORECAST TO SPREAD HEIGHT
FALLS INLAND ACROSS THE INTERIOR NW AND WRN CANADA BY THAT TIME.
HOWEVER...MODEL SCENARIOS BEGIN TO DIVERGE FROM ABOUT THAT POINT
FORWARD WITH HOW THE INCOMING PAC SYSTEM EVOLVES AND WHAT INFLUENCE
IT HAS ON DISLODGING THE CUT-OFF LOW.
THERE MAY BE A DAY OR TWO WHERE SCATTERED STRONG TO ISOLATED SEVERE
STORMS COULD DEVELOP ON THE PERIPHERY OF THE COLD CORE LOW AS
SMALLER SCALE PERTURBATIONS ORBIT AROUND THE LARGER CYCLONE. THIS
DEVELOPMENT COULD OCCUR AS LOCAL DIURNAL DESTABILIZATION AND
STRONGER CYCLONIC FLOW ALOFT BECOME FAVORABLY JUXTAPOSED TO SUSTAIN
CLUSTERS OF TSTMS FROM ONE DAY TO THE NEXT. PREDICTING A CORRIDOR OR
TWO OF ENHANCED STORM POTENTIAL AT THIS FORECAST RANGE DOES NOT
APPEAR LIKELY TO SUCCEED GIVEN THE EXTENSIVE NATURE OF THE
VERTICALLY STACKED COLD CORE SYSTEM AND THE LIMITED AREAL EXTENT OF
ANY REGIME SUPPORTIVE OF SEVERE TSTMS.
..CARBIN.. 09/22/2011
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