Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 021247
SWODY1
SPC AC 021246

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0746 AM CDT WED SEP 02 2015

VALID 021300Z - 031200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF WI...

...SUMMARY...
A FEW MARGINALLY SEVERE THUNDERSTORMS WITH STRONG WIND GUSTS WILL BE
POSSIBLE ACROSS PARTS OF WISCONSIN TODAY. NON-SEVERE THUNDERSTORMS
WILL ALSO BE POSSIBLE ACROSS PARTS OF THE EASTERN UNITED
STATES...GREAT LAKES REGION...FOUR CORNERS AREA AND SOUTHERN AND
CENTRAL ROCKIES.

...WISCONSIN...
A SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY...WILL MOVE SLOWLY
EWD TODAY ACROSS THE UPPER MS VALLEY. ELEVATED THUNDERSTORMS ARE
ONGOING THIS MORNING JUST AHEAD OF THE SHORTWAVE TROUGH FROM THE
ARROWHEAD OF MN AND WRN UPPER MI EXTENDING SWD INTO SCNTRL IA AND NW
MO. THE STORMS OVER NRN WI SHOULD CONTINUE TO MOVE ENEWD INTO UPPER
MI THIS MORNING AS CONVECTION FURTHER TO THE SOUTH IN WRN WI
GRADUALLY BECOMES MORE ISOLATED WITH TIME WHICH IS SUGGESTED BY THE
LATEST HRRR. THIS SHOULD SETUP A STRONG THERMAL GRADIENT ACROSS
WCNTRL WI...ALONG WHICH SFC-BASED THUNDERSTORMS SHOULD DEVELOP EARLY
THIS AFTERNOON. SFC DEWPOINTS IN THE UPPER 60S ACROSS MUCH OF CNTRL
WI SHOULD ALLOW FOR THE DEVELOPMENT OF MODERATE INSTABILITY...WHICH
COMBINED WITH LARGE-SCALE ASCENT ASSOCIATED WITH THE SHORTWAVE
TROUGH SHOULD SUPPORT A GRADUAL INCREASE IN STORM COVERAGE THIS
AFTERNOON. SFC-BASED STORMS ARE EXPECTED TO FIRST INITIATE IN WCNTRL
WI WITH THIS CONVECTION MOVING EWD INTO CNTRL WI BY EARLY AFTERNOON
EVENTUALLY REACHING THE WRN SHORE OF LAKE MICHIGAN BY LATE
AFTERNOON. NAM FORECAST SOUNDINGS IN CNTRL WI AT 21Z SHOW MLCAPE
NEAR 1500 J/KG...SOME DIRECTIONAL SHEAR FROM THE SFC TO 700 MB AND
25 TO 30 KT OF DEEP-LAYER SHEAR. THIS COMBINED WITH THE MOIST
BOUNDARY LAYER SHOULD BE ENOUGH FOR A MARGINAL WIND DAMAGE THREAT
WITH SHORT MULTICELL LINE SEGMENTS.

..BROYLES/GLEASON.. 09/02/2015



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