Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 290517
SWODY1
SPC AC 290515

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1215 AM CDT MON AUG 29 2016

VALID 291200Z - 301200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF THE
UPPER-MISSISSIPPI VALLEY...

...SUMMARY...
A MARGINAL SEVERE THREAT WITH STRONG WIND GUSTS AND HAIL WILL BE
POSSIBLE MONDAY ACROSS PARTS OF EASTERN SOUTH
DAKOTA...MINNESOTA...NORTHWEST WISCONSIN AND WESTERN PART OF THE
UPPER PENINSULA OF MICHIGAN.

...SYNOPSIS...
IN THE MID-UPPER LEVELS...AN EXPANSIVE RIDGE WILL PERSIST ACROSS
MUCH OF THE CONTIGUOUS UNITED STATES...WITH TROUGHS ALONG EACH COAST
BOOKENDING THIS RIDGE. WITHIN THIS BROAD MID-UPPER-LEVEL RIDGE...A
CLOSED LOW OVER THE SOUTHERN ROCKY MOUNTAINS WILL CONTINUE TO WEAKEN
AND FILL AS IT SLOWLY LIFTS NORTHEAST. AT THE SURFACE...A BROAD
ANTICYCLONE WILL SETTLE INTO THE OHIO VALLEY IN THE WAKE OF THE
PREVIOUS DAYS COLD FRONT. SOUTH/SOUTHWEST WINDS ON THE WESTERN
PERIPHERY OF THIS ANTICYCLONE WILL HELP TO MAINTAIN SURFACE
DEWPOINTS AT OR ABOVE 60F AHEAD OF AN APPROACHING COLD FRONT ACROSS
PORTIONS OF THE UPPER MISSISSIPPI VALLEY.

...UPPER MISSISSIPPI VALLEY...
THUNDERSTORMS MAY BE ONGOING AT THE START OF THE FORECAST PERIOD
WITHIN A MODEST WARM-AIR ADVECTION REGIME ACROSS PORTIONS OF
NORTHEAST MINNESOTA...NORTHWEST WISCONSIN...AND THE MICHIGAN UPPER
PENINSULA. MARGINALLY SEVERE HAIL MAY BE POSSIBLE WITHIN THE
STRONGEST THUNDERSTORM CORES. THESE THUNDERSTORMS SHOULD QUICKLY
MOVE EAST AND WEAKEN THROUGH LATE MORNING.

BY MID-LATE AFTERNOON...THUNDERSTORMS SHOULD DEVELOP ALONG AN
APPROACHING SURFACE COLD FRONT. AHEAD OF THIS FRONT...SURFACE
DEWPOINTS AT OR ABOVE 65F COUPLED WITH AFTERNOON HEATING WILL RESULT
IN STRONG DESTABILIZATION ACROSS WESTERN MINNESOTA AND EASTERN SOUTH
DAKOTA. DESPITE WEAK MID-LEVEL FLOW...A PLUME OF MID-LEVEL LAPSE
RATES AT OR ABOVE 7 C/KM WILL SUPPORT MARGINALLY SEVERE HAIL AND AN
ISOLATED SEVERE WIND GUST OR TWO WITH THE STRONGEST THUNDERSTORM
CORES. TO THE NORTHEAST OF THIS AREA...UNCERTAINTY REMAINS REGARDING
THE AMOUNT OF DESTABILIZATION THAT WILL OCCUR IN THE WAKE OF MORNING
CONVECTION. SHOULD THUNDERSTORMS DEVELOP HERE...STRONGER MID-LEVEL
FLOW THAN AREAS TO THE SOUTHWEST MAY OFFSET WEAKER INSTABILITY TO
SUPPORT MARGINALLY SEVERE HAIL AND A SEVERE WIND GUST OR TWO.

..MARSH/ROGERS.. 08/29/2016

$$



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