MODERATE RISK Today; Damaging Wind Threat Continues

Today’s Severe Threat

Thunderstorms continue to track southeast into the Ohio Valley with strong to severe thunderstorms possible through the daylight hours. The Storm Prediction Center has highlighted areas across the Ohio Valley under a MODERATE RISK today and tonight for the potential of hail, high winds and isolated tornadoes. The primary concern during the overnight hours looks to be damaging winds and heavy rain.

…SUMMARY…
MULTIPLE ROUNDS OF SEVERE THUNDERSTORMS CAPABLE OF DAMAGING
WINDS…TORNADOES AND LARGE HAIL ARE LIKELY TODAY AND TONIGHT ACROSS
MUCH OF THE MIDWEST…BUT ESPECIALLY ACROSS PORTIONS OF
ILLINOIS…INDIANA…AND KENTUCKY.

…CORN BELT AND OH VALLEY REGION THROUGH TONIGHT…
A SHORTWAVE TROUGH OVER THE NRN PLAINS/UPPER MS VALLEY…WITH
SEVERAL EMBEDDED SPEED MAXIMA…WILL PROGRESS SEWD AROUND THE NE
PERIPHERY OF A CLOSED UPPER HIGH OVER THE SRN PLAINS. AN ONGOING
MCS AND MCV NEAR CHICAGO AS OF 12Z WILL LIKELY CONTINUE TO MOVE SEWD
TODAY IN ASSOCIATION WITH THE INTERACTION OF ITS COLD POOL AND A
PRE-EXISTING FRONT FROM NE IL ACROSS WRN/SRN INDIANA TO NRN KY.
SURFACE HEATING/DESTABILIZATION IN ADVANCE OF THIS MCS SHOULD ALLOW
THE CONVECTION TO MAINTAIN INTENSITY THROUGH LATE MORNING AND INTO
THE AFTERNOON…WITH THE CONTINUED RISK FOR DAMAGING OUTFLOW GUSTS
FROM NE IL/NW INDIANA THIS MORNING INTO KY BY EARLY-MID AFTERNOON.
THE INTENSITY OF THE DAMAGING GUST RISK IS IN QUESTION AS FAR E AND
SE AS THE INDIANAPOLIS AND LOUISVILLE AREAS SINCE THE RELATIVELY
EARLY ARRIVAL OF THE MCS /ROUGHLY 16Z AT IND AND 19Z AT LOU/ WILL BE
SUBOPTIMAL WITH RESPECT TO DIURNAL DESTABILIZATION.

OUTFLOW TRAILING WWD AND NWWD FROM THIS EARLY MCS WILL PROVIDE A
FOCUS FOR ADDITIONAL SEVERE THUNDERSTORM DEVELOPMENT THIS
AFTERNOON/EVENING ACROSS EXTREME ERN IA INTO IL. STRONG TO EXTREME
BUOYANCY /MLCAPE OF 4000-5500 J PER KG/ IS EXPECTED ALONG THIS
BOUNDARY BY MID AFTERNOON AS SURFACE TEMPERATURES WARM TO NEAR 90 F
WITH MID-UPPER 70S BOUNDARY LAYER DEWPOINTS…BENEATH THE ERN EXTENT
OF AN ELEVATED MIXED LAYER PLUME. LOW-LEVEL ASCENT ALONG THE
REMNANT OUTFLOW SHOULD BE SUFFICIENT TO INITIATE ADDITIONAL STORMS
BY MID-LATE AFTERNOON…WITH STORMS SUBSEQUENTLY SPREADING SEWD
THROUGH THIS EVENING AND TONIGHT.

THE ENVIRONMENTAL PARAMETER SPACE /LARGE CAPE AND EFFECTIVE BULK
WIND DIFFERENCES AOA 50 KT/ FAVORS INTENSE SUPERCELLS WITH THE
INITIAL STORM DEVELOPMENT THIS AFTERNOON ACROSS EXTREME ERN IA INTO
NW AND CENTRAL IL. SOME ENHANCEMENT TO LOW-LEVEL SHEAR ALONG THE
OUTFLOW BOUNDARY…IN CONJUNCTION WITH THE EXTREME BUOYANCY AND RICH
MOISTURE…WILL SUPPORT THE RISK FOR A STRONG TORNADO OR TWO AND
VERY LARGE HAIL EARLY IN THE STORM EVOLUTION. THE CONVECTION SHOULD
GROW UPSCALE INTO ANOTHER MCS THIS EVENING WHILE SURGING SEWD/SSEWD
ACROSS IL…WITH AN ACCOMPANYING RISK FOR SWATHS OF DAMAGING WINDS.