The High Risk has been issued for eastern Illinois and much of Indiana, likely pointing to the Storm Prediction Center's concern over potentially tornadic cells that may develop as they coagulate with one another to form a powerful squall line. Categorical outlooks issued below tell the story; tornadoes and wind are the top two concerns for today.
|Damaging Wind Outlook|
Initiation of these storms is expected around the noon hour Central Time in Illinois, and further intensification will occur explosively until the 3:00 PM hour, before coagulation occurs and the storms race eastward towards the Ohio Valley at over 50 knots, per recent sounding analysis.
This is a dangerous situation. If you are in the Moderate Risk (red) or High Risk (pink) areas on the top image, you are advised to prepare for potentially extreme weather, which may include tornadoes (some strong), potentially extreme damaging winds, and hail. The scope of this now-likely outbreak is displayed on excerpts of the Storm Prediction Center write-up below.
...TORNADO OUTBREAK WITH MULTIPLE SIGNIFICANT TORNADOES AND
WIDESPREAD DAMAGING WINDS EXPECTED ACROSS THE OH VALLEY AND SRN
GREAT LAKES REGION TODAY...
...THE DEVELOPMENT OF A SQUALL-LINE APPEARS LIKELY DURING
THE LATE AFTERNOON ACROSS THE OH VALLEY WITH THE LINE DEVELOPING SWD
INTO THE TN VALLEY DURING THE EARLY EVENING.
0-3 KM STORM RELATIVE HELICITIES OF 400 TO 450 M2/S2 WILL BE
FAVORABLE FOR STRONG TORNADOES WITH SEVERAL LONG-TRACK DAMAGING
TORNADOES EXPECTED TO OCCUR FROM ERN IL ENEWD ACROSS MUCH OF WRN AND
CNTRL IND FROM LATE MORNING INTO EARLY AFTERNOON. AS CELL COVERAGE
INCREASES AHEAD OF THE FAST MOVING FRONT...A SQUALL-LINE SHOULD
ORGANIZE LATE THIS AFTERNOON. WIDESPREAD WIND DAMAGE WILL BE
ASSOCIATED WITH THE LINE ALONG WITH TORNADOES WITH ROTATING CELLS
EMBEDDED IN THE LINE. THE SEVERE THREAT SHOULD RAMP UP SOUTH OF THE
OH RIVER DURING THE LATE AFTERNOON AS CELLS INITIATE SWD ALONG THE
FRONT. THE POTENTIAL FOR WIND DAMAGE AND TORNADOES SHOULD DEVELOP AS
A FAR SOUTH AS THE TN VALLEY DURING THE EVENING AS AN EXTENSIVE LINE
OF SEVERE STORMS MOVES EWD INTO THE UPPER OH VALLEY AND CNTRL
SEVERAL FACTORS APPEAR TO BE COMING TOGETHER FOR A TORNADO OUTBREAK
ACROSS THE OH VALLEY. THE FIRST FACTOR IS THAT THE SYSTEM IS
NEGATIVELY-TITLED AND VERY WELL-ORGANIZED. THE SECOND IS THAT THE
LOW AND MID-LEVEL JETS WILL BECOME FAVORABLY COUPLED IN THE OH
VALLEY TODAY COINCIDING WITH AN OUTBREAK OF STORMS ACROSS THE WARM
SECTOR. THE THIRD IS THAT SUPERCELLS ARE EXPECTED TO REMAIN DISCRETE
INTO THE MID-AFTERNOON. THESE FACTORS COMBINED WITH EXTREMELY
FAVORABLE LOW-LEVEL SHEAR PROFILES JUSTIFIES THE ISSUANCE OF A HIGH
RISK ACROSS ERN IL...IND AND SW LOWER MI.