Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS48 KWNS 310841
SWOD48
SPC AC 310840

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0340 AM CDT WED AUG 31 2016

VALID 031200Z - 081200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS INCLUDING THE ECMWF AND GFS BEGIN THE DAY 4
TO 8 PERIOD WITH AN UPPER-LEVEL RIDGE OVER THE GREAT LAKES REGION
AND AN UPPER-LEVEL TROUGH IN THE WRN STATES. THE MODELS DEVELOP AN
AXIS OF INSTABILITY IN THE GREAT PLAINS ON SATURDAY/DAY 4 BENEATH
SOUTHWEST MID-LEVEL FLOW WHERE ISOLATED THUNDERSTORMS WILL BE
POSSIBLE SATURDAY AFTERNOON AND EVENING. THE ECMWF AND GFS SOLUTIONS
REMAIN IN DECENT AGREEMENT ON SUNDAY/DAY 5 WITH THE INSTABILITY AXIS
STILL IN THE CNTRL AND NRN PLAINS. THUNDERSTORMS WITH SOME SEVERE
THREAT WILL BE POSSIBLE ALONG THE NRN EDGE OF THE STRONGER
INSTABILITY IN THE NRN PLAINS SUNDAY AFTERNOON AND EVENING. ON
MONDAY/DAY 6 AND TUESDAY/DAY 7...THE DETAILS OF THE ECMWF AND GFS
SOLUTIONS DIVERGE SOMEWHAT BUT CONTINUE TO SUGGEST SOUTHWEST
MID-LEVEL FLOW WILL BE IN PLACE WITH A CORRIDOR OF MODERATE
INSTABILITY DEVELOPING FROM THE CNTRL PLAINS NEWD INTO THE UPPER MS
VALLEY. THUNDERSTORMS WITH SOME SEVERE THREAT WILL AGAIN BE POSSIBLE
ALONG THE INSTABILITY GRADIENT FROM NRN PARTS OF THE CNTRL PLAINS
NEWD INTO THE UPPER MS VALLEY. ON WEDNESDAY/DAY 8...THE MODELS
DIVERGE SHARPLY CONCERNING THE DETAILS BUT SUGGEST THE GREATEST
POTENTIAL FOR A SEVERE THREAT WILL BE IN THE UPPER MS VALLEY ON THE
NRN EDGE OF THE STRONGER INSTABILITY.

AT THIS POINT...THE DAY WITH THE GREATEST SEVERE THREAT COULD
POTENTIALLY BE ON MONDAY/DAY 6 AS A SHORTWAVE TROUGH AND ASSOCIATED
MID-LEVEL JET EJECT NEWD OUT OF THE CNTRL AND NRN ROCKIES. A 15
PERCENT CONTOUR COULD BE ADDED FOR PARTS OF THE CNTRL AND NRN PLAINS
EWD INTO THE UPPER MS VALLEY IF LATER MODEL RUNS CONTINUE TO SHOW
THIS FEATURE MOVING NEWD ACROSS THE NCNTRL STATES ON MONDAY.

..BROYLES.. 08/31/2016



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