Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 290858
SWOD48
SPC AC 290856

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0356 AM CDT MON AUG 29 2016

VALID 011200Z - 061200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS INCLUDING THE ECMWF AND GFS BEGIN THE DAY 4
TO 8 PERIOD WITH AN UPPER-LEVEL TROUGH OVER THE ERN U.S. AND A
HIGH-AMPLITUDE UPPER-LEVEL RIDGE OVER THE GREAT PLAINS. ON
THURSDAY/DAY 4...THE NATIONAL HURRICANE CENTER IS FORECASTING A
TROPICAL STORM TO MOVE ACROSS CNTRL FL. IF THIS TAKES PLACE...AN
ISOLATED TORNADO THREAT WOULD BE POSSIBLE ACROSS PARTS OF THE FL
PENINSULA DEPENDING UPON THE STRENGTH OF THE TROPICAL SYSTEM.
THUNDERSTORMS COULD ALSO DEVELOP ON THURSDAY AHEAD OF THE ERN U.S.
UPPER-LEVEL TROUGH AND IN THE SRN PLAINS ALONG THE SERN PERIPHERY OF
THE UPPER-LEVEL RIDGE. THE NAM AND GFS MOVE THE UPPER-LEVEL RIDGE
EWD INTO THE MID MO VALLEY AND UPPER MS VALLEY ON FRIDAY/DAY 5. THE
TROPICAL STORM IS FORECAST TO MOVE FROM THE FL PENINSULA INTO THE
WRN ATLANTIC ON FRIDAY BUT UNCERTAINTY CONCERNING THE STRENGTH AND
TIMING OF THE TROPICAL SYSTEM IS SUBSTANTIAL. ON SATURDAY/DAY 6 AND
SUNDAY/DAY 7...BOTH THE ECMWF AND GFS MOVE THE UPPER-LEVEL TROUGH
EWD INTO THE ATLANTIC AND ESTABLISH SOUTHWEST MID-LEVEL FLOW OVER
THE WRN AND NCNTRL STATES. A SEVERE THREAT COULD DEVELOP SATURDAY
AFTERNOON OR SUNDAY AFTERNOON ALONG AN AXIS OF INSTABILITY IN THE
CNTRL AND NRN PLAINS EWD INTO THE MID MO VALLEY. ON MONDAY/DAY
8...THE ECMWF AND GFS MOVE THE POTENTIAL FOR SEVERE STORMS EWD INTO
THE UPPER MS VALLEY EXTENDING SWWD INTO THE MID MO VALLEY. AT THIS
POINT...CONSIDERABLE UNCERTAINTY EXISTS THROUGHOUT THE DAY 4 TO 8
PERIOD CONCERNING THE POSITIONING AND MAGNITUDE OF ANY SEVERE THREAT
AND WILL NOT ADD PROBABILITY CONTOURS UNTIL THE MODELS CAN SHOW MORE
RUN TO RUN CONSISTENCY.

..BROYLES.. 08/29/2016



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