DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 170554
SWODY1
SPC AC 170552

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST SAT NOV 16 2013

VALID 171200Z - 181200Z

...THERE IS A HIGH RISK OF SVR TSTMS ACROSS PARTS OF ERN IL...IND
AND FAR SW LOWER MI...

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF IL...LOWER
MI...OH...IND...KY AND WRN TN......

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID TO
UPPER MS VALLEY...OH VALLEY...SRN GREAT LAKES AND TN VALLEY...

...TORNADO OUTBREAK WITH MULTIPLE SIGNIFICANT TORNADOES AND
WIDESPREAD DAMAGING WINDS EXPECTED ACROSS THE OH VALLEY AND SRN
GREAT LAKES REGION TODAY...

AN IMPRESSIVE NEGATIVELY-TILTED UPPER-LEVEL TROUGH AND POWERFUL 80
TO 100 KT MID-LEVEL JET WILL MOVE ACROSS THE NCNTRL U.S. TODAY. AT
THE SFC...A LOW WILL TRACK NEWD INTO THE UPPER MIDWEST AS A COLD
FRONT ADVANCES EWD INTO THE MID TO UPPER MS VALLEY. AHEAD OF THE
FRONT...STRONG MOISTURE ADVECTION WILL OCCUR DUE TO A WELL-DEVELOPED
AND BROAD 60 TO 75 KT LOW-LEVEL JET. AN EXTENSIVE AREA OF
THUNDERSTORMS WITH AN ISOLATED SEVERE THREAT SHOULD BE ONGOING ALONG
THE ERN EDGE OF THE LOW-LEVEL JET FROM NE AR NEWD INTO SRN IND AT
DAYBREAK WITH THIS ACTIVITY MOVING EWD AWAY FROM THE INSTABILITY
AXIS THIS MORNING. FURTHER TO THE WEST...THE LOW-LEVEL JET WILL
TRANSPORT LOW TO MID 60S F SFC DEWPOINTS INTO THE MID MS VALLEY AND
OH VALLEY RESULTING IN A CORRIDOR OF MODERATE INSTABILITY FROM NE AR
NNEWD INTO CNTRL IL BY MID MORNING. DUE TO STRONG LARGE-SCALE ASCENT
ASSOCIATED WITH THE UPPER-LEVEL TROUGH...SFC-BASED CELL INITIATION
SHOULD OCCUR AHEAD OF THE FRONT BY MID MORNING ACROSS NRN AND CNTRL
IL WITH STORM COVERAGE EXPANDING EWD INTO IND AND LOWER MI BY EARLY
AFTERNOON. ALTHOUGH CELLS MAY REMAIN DISCRETE THROUGH MUCH OF THE
AFTERNOON...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.

FORECAST SOUNDINGS AT URBANA IL AND INDIANAPOLIS IND IN THE 18Z TO
21Z TIMEFRAME SHOW SBCAPE NEAR 1500 J/KG...0-6 KM SHEAR AROUND 70
KT...LOW-LCL HEIGHTS AND LONG LOOPED HODOGRAPHS SUGGESTING
SUPERCELLS AND TORNADOES WILL BE LIKELY AS DISCRETE CELLS INTENSIFY.
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
APPALACHIAN MTNS.

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.

..BROYLES/BUNTING.. 11/17/2013

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