Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS48 KWNS 300811
SWOD48
SPC AC 300810

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0310 AM CDT TUE AUG 30 2016

VALID 021200Z - 071200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS INCLUDING THE ECMWF AND GFS MODELS BEGIN THE
DAY 4 TO 8 PERIOD WITH AN UPPER-LEVEL RIDGE OVER THE NCNTRL U.S. AND
HAVE AN UPPER-LEVEL TROUGH ALONG THE ERN SEABOARD. THE UPPER-LEVEL
RIDGE IS FORECAST TO MOVE EWD ACROSS THE UPPER MS VALLEY INTO THE
WRN GREAT LAKES REGION ON FRIDAY/DAY 4 AS AN UPPER-LEVEL TROUGH
MOVES ACROSS THE WRN STATES. BOTH THE ECMWF AND GFS SOLUTIONS
DEVELOP AN AXIS OF INSTABILITY IN THE CNTRL AND NRN HIGH PLAINS ON
FRIDAY...ALONG WHICH ISOLATED THUNDERSTORMS WILL BE POSSIBLE DURING
THE LATE AFTERNOON AND EARLY EVENING. BOTH SOLUTIONS ESTABLISH
SOUTHWEST MID-LEVEL FLOW ACROSS THE NCNTRL STATES ON SATURDAY/DAY 5
INTO SUNDAY/DAY 6 AND MAINTAIN AN AXIS OF INSTABILITY IN THE GREAT
PLAINS WHERE SOME SEVERE THREAT WILL BE POSSIBLE FROM SATURDAY
AFTERNOON TO SUNDAY EVENING. ON MONDAY/DAY 7 AND TUESDAY/DAY 8...THE
ECMWF AND GFS SOLUTIONS CONTINUE TO SHOW SOUTHWEST MID-LEVEL FLOW IN
THE NCNTRL U.S. WITH AN UPPER-LEVEL TROUGH IN THE WRN STATES. THE
GFS IS MORE AMPLIFIED WITH THE UPPER-LEVEL TROUGH AND SLOWER TO MOVE
THE SYSTEM TO THE EAST THAN THE ECMWF. IN SPITE OF THE
DIFFERENCES...BOTH SOLUTIONS SHOW A POCKET OF INSTABILITY IN THE
CNTRL PLAINS TO MID MO VALLEY FROM MONDAY INTO TUESDAY. THIS AREA
WOULD HAVE POTENTIAL FOR A SEVERE THREAT BUT UNCERTAINTY IS
SUBSTANTIAL THIS LATE IN THE PERIOD.

A SEVERE THREAT WILL BE POSSIBLE EACH AFTERNOON AND EVENING FROM
SATURDAY/DAY 5 TO TUESDAY/DAY 8 MAINLY FROM THE CNTRL AND NRN PLAINS
INTO THE MID MO VALLEY. HOWEVER...WILL NOT ADD A SEVERE THREAT
CONTOUR IN THE NCNTRL U.S. FOR THE DAY 4 TO 8 PERIOD UNTIL MODEL
AGREEMENT AND PREDICTABILITY INCREASE CONCERNING THE FINER-SCALE
DETAILS.

..BROYLES.. 08/30/2016



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