Oct 18, 2007 2000 UTC Day 1 Convective Outlook
Updated: Thu Oct 18 20:24:18 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms with tornadoes are expected over parts of the lower ohio and tennessee valleys and lower mi this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20071018 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20071018 2000 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20071018 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20071018 2000 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 182021
   
   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0321 PM CDT THU OCT 18 2007
   
   VALID 182000Z - 191200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SRN LOWER
   MI...IND...WRN OH...ERN AND SRN IL...WRN KY...SE MO...WRN TN AND FAR
   NE AR...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT
   LAKES...OH VALLEY...TN VALLEY AND CNTRL GULF COAST STATES...
   
   CORRECTED FOR WORDING TN VALLEY SECTION
   
   ...SEVERE WEATHER OUTBREAK IS EXPECTED THIS AFTERNOON AND EVENING
   ACROSS PARTS OF THE SRN GREAT LAKES...LOWER OH VALLEY...MID-MS
   VALLEY AND TN VALLEY...
   
   ...GREAT LAKES REGION/LOWER OH VALLEY...
   A POWERFUL NEGATIVELY TILTED UPPER-LEVEL LOW IS EVIDENT ON WATER
   VAPOR IMAGERY OVER THE UPPER MIDWEST. A FRONT CURRENTLY EXTENDS SWD
   FROM AN ERN MN 980 MB SFC LOW ACROSS ERN IA AND ERN MO. AHEAD OF THE
   FRONT...MODERATE INSTABILITY IS PRESENT FROM IND EXTENDING SWD
   ACROSS WRN KY WHERE MLCAPE VALUES ARE IN THE 1000 TO 2000 J/KG
   RANGE. DESTABILIZATION SHOULD CONTINUE ACROSS THE WARM SECTOR WHICH
   COMBINED WITH STRONG LARGE-SCALE ASCENT AHEAD OF A PRONOUNCED DRY
   SLOT SHOULD RESULT IN WIDESPREAD CONVECTIVE DEVELOPMENT ACROSS THE
   REGION LATE THIS AFTERNOON. A SQUALL-LINE SHOULD ORGANIZE JUST AHEAD
   OF THE FRONT AND MOVE EWD INTO SRN LOWER MI...IND AND CNTRL KY.
   
   A WELL-DEFINED 100 KT MID-LEVEL JET IS CURRENTLY LOCATED FROM THE
   OZARK REGION EXTENDING NEWD INTO THE SRN GREAT LAKES. THIS JET IS
   CREATING VERY STRONG VERTICAL SHEAR PROFILES ACROSS THE REGION WHICH
   WILL BE FAVORABLE FOR SEVERAL ORGANIZED SEVERE LINE-SEGMENTS.
   REGIONAL WSR-88D VWPS ACROSS KY...IND AND LOWER MI SHOW SUBSTANTIAL
   LOW-LEVEL DIRECTIONAL AND SPEED SHEAR WHICH SHOULD ALSO BE FAVORABLE
   FOR LONG-LIVED SUPERCELLS ESPECIALLY LATE THIS AFTERNOON WITH STORMS
   THAT REMAIN DISCRETE. 0-3 KM SRH VALUES ABOVE 250 M2/S2 ACROSS MUCH
   OF THE REGION SUGGESTS STRONG TORNADOES WILL BE POSSIBLE ACROSS MANY
   AREAS. THE WIND DAMAGE THREAT SHOULD BECOME MORE DOMINANT AS A
   SQUALL-LINE DEVELOPS AND STORMS BECOME LINEAR IN NATURE DURING THE
   EVENING. AN ENHANCED WIND DAMAGE POTENTIAL WILL LIKELY DEVELOP WITH
   THE FASTER MOVING LINE-SEGMENTS/BOW ECHOES EMBEDDED IN THE LINE.
   TORNADOES WILL ALSO BE POSSIBLE THIS EVENING WITH ROTATING STORMS
   EMBEDDED IN THE LINE OR AHEAD OF THE LINE ACROSS THE WARM SECTOR.
   THE SEVERE THREAT SHOULD PERSIST THROUGH MUCH OF THE NIGHT WITH THE
   THREAT BECOMING MORE ISOLATED SOMETIME AFTER MIDNIGHT AS INSTABILITY
   DECREASES.
   
   ...TN VALLEY/CNTRL GULF COAST STATES...
   THE LATEST WATER VAPOR IMAGERY CURRENTLY SHOWS A WELL-DEVELOPED
   UPPER LEVEL-TROUGH LOCATED ACROSS THE SRN PLAINS. A BAND OF
   MID-LEVEL MOISTURE LIKELY ASSOCIATED WITH THE LEADING EDGE OF ASCENT
   IS LOCATED FROM NE TX ACROSS AR INTO SRN IL. A FRONTAL BOUNDARY
   EXISTS ALONG THIS CORRIDOR AND WIDESPREAD THUNDERSTORMS SHOULD
   DEVELOP AHEAD OF THE BOUNDARY...MOVING EWD ACROSS THE REGION LATE
   THIS AFTERNOON INTO THE EVENING. THUNDERSTORMS WILL ALSO CONTINUE TO
   AFFECT ERN MS AND AL ASSOCIATED WITH AN ONGOING MCS. A SQUALL-LINE
   SHOULD ORGANIZE ALONG THE FRONT OVERNIGHT AND MOVING EWD ACROSS THE
   CNTRL GULF COAST STATES THROUGH LATE TONIGHT.
   
   THE LATEST OBJECTIVE ANALYSIS SHOWS A 100 MID-LEVEL JET OVER THE SRN
   PLAINS WITH THE SERN EDGE OF THE JET LOCATED ACROSS THE LOWER MS
   VALLEY AND TN VALLEY. 50 TO 60 KT WINDS ALOFT ARE CREATING MODERATE
   TO STRONG VERTICAL SHEAR PROFILES FROM SRN MS AND CNTRL AL NWD TO
   TN. THIS ALONG WITH BACKED SSELY SFC WINDS ACROSS AL...THE FL
   PANHANDLE AND WRN GA IS CREATING WIND PROFILES FAVORABLE FOR
   SUPERCELLS AND TORNADOES. IN ADDITION...THE TORNADO THREAT SHOULD
   INCREASE LATE THIS AFTERNOON ACROSS WRN AND CNTRL MS AS SUPERCELLS
   AND SEVERE LINE SEGMENTS ORGANIZE AHEAD OF AN APPROACHING FRONT. THE
   LATEST WSR-88D VWPS ACROSS CNTRL MS AND CNTRL AL SHOW 0-1 KM SHEAR
   VALUES IN THE 20 TO 30 KT RANGE. IN ADDITION...SFC DEWPOINTS IN THE
   LOWER TO MID 70S F ARE CREATING LOW LCL HEIGHTS. THESE FACTORS WILL
   BE FAVORABLE FOR TORNADOES WITH THE MORE PERSISTENT SUPERCELLS. A
   FEW STRONG TORNADOES MAY ALSO OCCUR ACROSS THE REGION. AS THE
   SQUALL-LINE DEVELOPS AND MOVES EWD ACROSS TN...MS AND AL LATER THIS
   EVENING INTO THE OVERNIGHT PERIOD...WIND DAMAGE SHOULD BECOME THE
   MORE DOMINATE MODE OF SEVERE. THE SEVERE THREAT SHOULD BECOME MORE
   ISOLATED AFTER MIDNIGHT AS INSTABILITY DECREASES ACROSS THE REGION.
   
   ..BROYLES.. 10/18/2007
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z