MESO: Mesoscale Discussion 2162

ACUS11 KWNS 121815
SWOMCD
SPC MCD 121815
MIZ000-WIZ000-MNZ000-122015-

MESOSCALE DISCUSSION 2162
NWS STORM PREDICTION CENTER NORMAN OK
0115 PM CDT MON SEP 12 2011

AREAS AFFECTED...MN ARROWHEAD / NRN WI / WRN U.P. MICH

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 121815Z - 122015Z

CONVECTIVE TRENDS WILL BE MONITORED REGARDING THE POSSIBLE NEED FOR
A SEVERE WW THIS AFTERNOON INTO THE EARLY EVENING HOURS. AN ISOLD
SEVERE THREAT IS EXPECTED TO SHIFT EWD FROM INITIALLY THE MN
ARROWHEAD S AND E INTO NRN WI AND THE WRN U.P. OF MICH.

EARLY AFTERNOON SUBJECTIVE SURFACE ANALYSIS SHOWS A TROUGH/LOW LEVEL
CONFLUENCE ZONE /EXTENDING FROM THE MN ARROWHEAD SWWD INTO W-CNTRL
MN/ AHEAD OF AN ADVANCING COLD FRONT THAT EXTENDS FROM A LOW 130 MI
NE INL SWWD INTO SERN ND. THE PREFRONTAL WARM SECTOR IS
DESTABILIZING WITH AOA 1000 J/KG MLCAPE DEVELOPING BY MID AFTERNOON
AS TEMPS WARM THROUGH THE 70S. AS UPPER FORCING FOR ASCENT
ASSOCIATED WITH A POTENT SHORTWAVE TROUGH MOVING INTO THE REGION
COMBINES WITH FRONTAL LIFT...THIS WILL LEAD TO THE REMOVAL OF THE
CAP AND LEAD TO SCTD STORMS LATER TODAY.

CHANCES FOR STORM INITIATION/INCREASE IN STORM COVERAGE IS EXPECTED
BY MID-LATE AFTERNOON ALONG A WEAK LOW LEVEL CONFLUENCE ZONE/SURFACE
TROUGH AS IT IS OVERTAKEN BY THE FRONT OVER THE MN ARROWHEAD. SOME
QUESTION REMAINS REGARDING THE DURATION OF THE THREAT ACROSS THIS
REGION AS THE FRONT IS EXPECTED TO MOVE INTO WRN LK SUPERIOR BY LATE
AFTERNOON. FARTHER SE ACROSS NRN WI INTO WRN U.P. MICH...RECENT
RUNS OF STORM RESOLVING MODEL GUIDANCE DEVELOP STORMS IN THE 22-02Z
PERIOD. FORECAST SOUNDINGS SHOW STEEP LAPSE RATE PROFILES WITHIN AN
INCREASING/STRONG WIND PROFILE WHICH SHOULD SUPPORT AN ISOLD LARGE
HAIL/SEVERE WIND RISK...ESPECIALLY AS STORMS RESPOND TO THE
MAGNITUDE OF LINEAR FORCING THAT WOULD SUPPORT UPSCALE GROWTH INTO
AN EVENTUAL LINE SEGMENT.

..SMITH.. 09/12/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MQT...GRB...DLH...ARX...MPX...

LAT...LON 46619270 47609252 48379219 48499127 48088823 47088779
46048856 45089079 45749203 46619270

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