ACUS11 KWNS 261434
SWOMCD
MESOSCALE DISCUSSION 1620
NWS STORM PREDICTION CENTER NORMAN OK
0934 AM CDT TUE AUG 26 2014
AREAS AFFECTED...PORTIONS OF NRN IL...NWRN INDIANA...SERN WI
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 261434Z - 261630Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...THUNDERSTORMS CROSSING THE REGION THIS MORNING COULD
PRODUCE ISOLATED MARGINALLY SVR WIND/HAIL. WHILE CONVECTIVE TRENDS
WILL CONTINUE TO BE MONITORED...WW ISSUANCE IS CURRENTLY UNLIKELY.
DISCUSSION...THE REMNANTS OF NOCTURNAL CONVECTION THAT EVOLVED FROM
ERN NEB TO IA HAVE CROSSED THE MS RIVER...PRESENTLY REACHING A LINE
FROM ROCKFORD TO MOLINE. CAPPI DATA AT 9 KM INDICATE SUSTENANCE OF
ONGOING MULTICELL CLUSTERS...WHICH ARE APPROACHING A SFC BOUNDARY
DRAPED FROM THE CHICAGO AREA INTO W-CNTRL IL. THE 12Z ILX RAOB AND
SFC OBSERVATIONS SUGGEST RICH BOUNDARY-LAYER MOISTURE IN PROXIMITY
TO AND ON THE WARM SIDE OF THIS BOUNDARY -- E.G. LOWEST-100-MB MEAN
MIXING RATIO AROUND 16 G/KG. DIURNAL HEATING OF THIS MOISTURE WILL
BOOST BUOYANCY...WITH MLCAPE LIKELY REACHING 1500-2500 J/KG DURING
THE NEXT FEW HOURS.
ONGOING MULTICELL CLUSTERS WILL APPROACH/CROSS THE BOUNDARY --
INCLUDING THE CHICAGO AREA IN THE 1545-1700Z TIME FRAME -- AND A
RISK FOR INTENSE UPDRAFTS/DOWNDRAFTS WILL EXIST. LOT AND MKX VWPS
SAMPLE 25-30 KT WLYS IN THE 1-4-KM LAYER...WHICH WILL BOLSTER
CONVECTIVE MOMENTUM TRANSPORT TO POTENTIALLY YIELD ISOLATED DMGG
WIND GUSTS. ISOLATED MARGINALLY SVR HAIL CANNOT BE RULED OUT.
HOWEVER...ONLY MODEST MID-LEVEL FLOW/DEEP SHEAR YIELD UNCERTAINTY IN
A MORE ORGANIZED...SUSTAINED SVR RISK. NEVERTHELESS...CONVECTIVE
TRENDS WILL CONTINUE TO BE MONITORED.
..COHEN/MEAD.. 08/26/2014
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...MKX...DVN...
LAT...LON 42718878 42768753 41468694 40878805 41458932 42718878
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