ACUS11 KWNS 071800
SWOMCD
MESOSCALE DISCUSSION 1654
NWS STORM PREDICTION CENTER NORMAN OK
0100 PM CDT WED SEP 07 2016
AREAS AFFECTED...PORTIONS OF NRN/WRN IL...NERN MO...ERN IA...SRN WI
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 071800Z - 072030Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...THE RISK FOR ISOLATED SVR TSTMS CAPABLE OF PRODUCING DMGG
WIND GUSTS AND PERHAPS A TORNADO IS INCREASING. WHILE WW ISSUANCE IS
PRESENTLY UNLIKELY...CONVECTIVE/ENVIRONMENTAL TRENDS WILL CONTINUE
TO BE MONITORED.
DISCUSSION...TO THE SE OF A WIDESPREAD CLOUD CANOPY COVERING
PORTIONS OF WI THROUGH CNTRL/WRN IA AND INTO NWRN MO...THE AIR MASS
IS DESTABILIZING OWING TO INSOLATION AMIDST SFC DEWPOINTS IN THE
MIDDLE 70S. WITH MLCAPE INCREASING TO 1000-2000 J/KG AND LIMITED
MLCINH...TSTMS WILL INCREASE IN NUMBER/INTENSITY OWING TO...
/1/ FORCING FOR ASCENT ACCOMPANYING A LONG-LIVED ENEWD-MOVING MCV
PRESENTLY CROSSING S-CNTRL IA...
/2/ ASCENT ALONG A NRN-IL OUTFLOW BOUNDARY DEPOSITED BY CONVECTION
MOVING THROUGH/E OF THE CHICAGO AREA...
/3/ BAROCLINIC CIRCULATIONS IN PROXIMITY TO THE
CLOUD-COVERAGE-GRADIENT DRIVEN BY DIFFERENTIAL HEATING...AND
/4/ ASCENT RELATED TO DIURNALLY BOLSTERED BOUNDARY-LAYER
CIRCULATIONS AMIDST NEGLIGIBLE CAPPING.
GIVEN THE AFOREMENTIONED DEGREE OF BUOYANCY...COMBINED WITH AROUND
25-45 KT OF EFFECTIVE SHEAR...ORGANIZED CONVECTIVE STRUCTURES
INCLUDING SMALL BOWING SEGMENTS -- AND PERHAPS A FEW TRANSIENT
SUPERCELL STRUCTURES -- COULD EVOLVE. ISOLATED DMGG WIND GUSTS
SHOULD BE THE PRIMARY HAZARD. HOWEVER...VWPS AT LOT/ILX/DVN ARE
SAMPLING AROUND 20-30 KT OF FLOW IN THE 1-2-KM-AGL LAYER...OFFERING
SUFFICIENT LOW-LEVEL SHEAR FOR A MARGINAL RISK FOR A BRIEF/WEAK
TORNADO.
POOR MID-LEVEL LAPSE RATES...AND THE LACK OF A MORE SALIENT
MID-LEVEL PERTURBATION...SHOULD PREVENT A MORE SUBSTANTIAL SVR RISK
FROM EVOLVING. HOWEVER...IF A MORE FOCUSED CORRIDOR OF SVR WIND
AND/OR TORNADO POTENTIAL WERE TOO EVOLVE...IT IS POSSIBLE THAT
WW-ISSUANCE PROBABILITIES COULD INCREASE LATER THIS AFTERNOON.
..COHEN/HART.. 09/07/2016
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...ILX...MKX...LSX...DVN...ARX...DMX...
LAT...LON 40609222 41349198 42709068 42968847 42298771 41548789
40478996 39889133 39939198 40609222
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