Nov 17, 2013 0600 UTC Day 1 Convective Outlook
Updated: Sun Nov 17 05:56:44 UTC 2013 (20131117 1200Z Day 1 shapefile | 20131117 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20131117 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20131117 1200 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20131117 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20131117 1200 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
HIGH 35,138 6,232,779 Indianapolis, IN...South Bend, IN...Terre Haute, IN...West Lafayette, IN...Paxton, IL...
MODERATE 145,478 36,518,950 Chicago, IL...Columbus, OH...Detroit, MI...Louisville, KY...Milwaukee, WI...
SLIGHT 284,078 31,116,631 Memphis, TN...Nashville, TN...Cleveland, OH...St. Louis, MO...Pittsburgh, PA...
   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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