ACUS11 KWNS 072037
SWOMCD
MESOSCALE DISCUSSION 1658
NWS STORM PREDICTION CENTER NORMAN OK
0336 PM CDT WED SEP 07 2016
AREAS AFFECTED...PORTIONS OF NRN IL...SRN WI...FAR NWRN INDIANA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 072036Z - 072300Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING POTENTIAL
FOR DMGG WIND GUSTS AND POSSIBLE ISSUANCE OF A WW.
DISCUSSION...TSTMS HAVE ORGANIZED FROM SRN WI TO THE ERN IA/NWRN IL
BORDER IN ASSOCIATION WITH ASCENT PRECEDING A LONG-LIVED MCV.
EMBEDDED BOWING STRUCTURES HAVE OCCASIONALLY BECOME EVIDENT WITHIN A
QUASI-LINEAR CONVECTIVE SEGMENT CROSSING THE MS RIVER...AND THIS
LINE WILL CONTINUE ADVANCING EWD/ENEWD THROUGH THE LATE
AFTERNOON/EARLY EVENING -- PERHAPS EVENTUALLY AFFECTING THE CHICAGO
METROPOLITAN AREA AND VICINITY. STRONG SFC HEATING AMIDST DEWPOINTS
IN THE LOWER/MIDDLE 70S HAS BOOSTED MLCAPE TO AROUND 1500-2500 J/KG
WITH NEGLIGIBLE MLCINH IN ADVANCE OF THIS ACTIVITY. THIS SHOULD
SUPPORT CONVECTIVE MAINTENANCE FOR THE NEXT SEVERAL HOURS...GIVEN
25-40 KT OF EFFECTIVE SHEAR IN PLACE. POOR MID-LEVEL LAPSE RATES AND
ONLY MODEST LOW-LEVEL FLOW SAMPLED BY THE LOT VWP MAY LIMIT THE
OVERALL SVR RISK. HOWEVER...THE UPSTREAM DVN VWP IS SAMPLING AROUND
30-40 KT OF FLOW IN THE 1-2-KM-AGL LAYER...AND LOW-LEVEL FLOW COULD
INCREASE ACROSS THE REGION RELATED TO THE PASSAGE OF A SUBTLE
MID-LEVEL SPEED MAX. THIS COULD LOCALLY ENHANCE THE SVR-WIND RISK
VIA CONVECTIVE MOMENTUM TRANSPORT...ESPECIALLY AS CONVECTION
ENCOUNTERS STEEPER LOW-LEVEL LAPSE RATES ACROSS N-CNTRL/NERN IL AND
VICINITY.
..COHEN/HART.. 09/07/2016
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...ILX...MKX...DVN...
LAT...LON 40629055 41629036 42428976 42838879 42758777 42298736
41388718 40398830 40198991 40629055
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