AREAS AFFECTED...CNTRL AND SRN WI INTO NRN IL
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 200046Z - 200145Z
PROBABILITY OF WATCH ISSUANCE...80 PERCENT
SUMMARY...AN INCREASING SEVERE WEATHER THREAT IS ANTICIPATED TO THE
EAST OF TORNADO WATCHES 180 AND 183 LATE THIS EVENING INTO TONIGHT.
THE PRIMARY HAZARDS WILL BE DAMAGING WINDS AND HAIL...THOUGH A
TORNADO OR TWO WILL BE POSSIBLE A NEW WATCH WILL LIKELY BE REQUIRED
WITHIN THE HOUR.
DISCUSSION...THE 00Z DVN AND ILX SOUNDINGS SHOWED THAT THE LOCAL
ENVIRONMENT REMAINS MODERATELY UNSTABLE THIS EVENING OWING TO STEEP
LOW TO MIDLEVEL LAPSE RATES AND A MOIST PBL WHERE LOWEST 100-MB
MEAN-MIXING RATIOS OF AROUND 13.5 G/KG WERE OBSERVED. THOUGH SFC
TEMPERATURES WILL START TO COOL...THE MOIST ENVIRONMENT COUPLED WITH
THE ABSENCE OF ANY APPRECIABLE CAP SHOULD MAINTAIN MODERATE
INSTABILITY INTO THE OVERNIGHT HOURS. AS SUCH...EXPECT ONGOING
BOWING TSTM COMPLEX OVER NWRN IL TO PERSIST...WITH ADDITIONAL STORMS
DEVELOPING ACROSS DISCUSSION AREA WITHIN THE EXIT REGION OF A 40-50
KT NOCTURNAL LOW-LEVEL WIND MAXIMUM WHERE WAA AND ISENTROPIC ASCENT
WILL BE ENHANCED. GIVEN A STEADY STRENGTHENING TO THE MID AND
UPPER-TROPOSPHERIC FLOW FIELD...THE ENVIRONMENT WILL BE SUPPORTIVE
OF EMBEDDED SUPERCELL AND BOWING STRUCTURES CAPABLE DAMAGING
WINDS...HAIL...AND PERHAPS A TORNADO OR TWO.
..MEAD/CORFIDI.. 05/20/2013
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...GRB...LOT...ILX...MKX...DVN...ARX...
LAT...LON 41209149 42899142 44019123 44449049 44448946 44108892
43218874 41818885 41208885 40818957 40889068 41209149
