Sep 11, 2013 1630 UTC Day 1 Convective Outlook
Updated: Wed Sep 11 16:01:44 UTC 2013 (20130911 1630Z Day 1 shapefile | 20130911 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130911 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130911 1630 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
20130911 1630 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
20130911 1630 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
SLIGHT 170,246 26,881,793 Columbus, OH...Detroit, MI...Cleveland, OH...Pittsburgh, PA...Toledo, OH...
   SPC AC 111558

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1058 AM CDT WED SEP 11 2013

   VALID 111630Z - 121200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER GREAT LAKES AND
   UPPER OH VALLEY INTO NRN NEW ENGLAND...

   ...SYNOPSIS...

   A SIGNIFICANT SHORT-WAVE TROUGH OVER CNTRL MANITOBA WILL PROGRESS
   SEWD CONTRIBUTING TO THE AMPLIFICATION OF A LONG-WAVE TROUGH OVER
   CNTRL/ERN CANADA INTO THE UPPER MS VALLEY AND GREAT LAKES.  A
   LOWER-AMPLITUDE IMPULSE /NOW OVER THE UPPER GREAT LAKES/ WILL
   PRECEDE THE MANITOBA SYSTEM...EJECTING ENEWD ALONG THE ST. LAWRENCE
   VALLEY.  

   IN THE LOW LEVELS...MID-MORNING SURFACE ANALYSIS SHOWED A
   SLOW-MOVING COLD FRONT EXTENDING FROM LOW PRESSURE OVER CNTRL QUEBEC
   SWWD THROUGH THE UPPER GREAT LAKES INTO THE MID MO VALLEY AND CNTRL
   HIGH PLAINS.  THIS BOUNDARY WILL CONTINUE TO SLOWLY SETTLE SEWD WITH
   THE WRN SEGMENT BEING OVERTAKEN BY A STRONGER...MORE PROGRESSIVE
   COLD FRONT ADVANCING OUT OF THE NRN PLAINS AND UPPER MS VALLEY. 

   ...LOWER GREAT LAKES/UPPER OH VALLEY INTO NEW ENGLAND THIS AFTERNOON
   INTO TONIGHT...

   LATEST MODEL GUIDANCE INDICATES A COMPLEX CONVECTIVE EVOLUTION TODAY
   WITH STORMS FORMING ALONG THE SEWD-MOVING COLD FRONT...LAKE BREEZE
   CIRCULATIONS...AND WITHIN THE OPEN WARM SECTOR AS BACKGROUND FORCING
   FOR ASCENT IS ENHANCED BY THE LEAD SHORT-WAVE TROUGH MOVING ACROSS
   THE GREAT LAKES.  ABUNDANT SUNSHINE COUPLED WITH A SEASONABLY MOIST
   AIR MASS WILL CONTRIBUTE TO MODERATE TO STRONG INSTABILITY BY
   AFTERNOON WITH MLCAPE VALUES APPROACHING 2000-3000+ J/KG.  

   THE STRONGEST VERTICAL SHEAR /I.E. EFFECTIVE BULK SHEAR MAGNITUDES
   OF 35-50 KT/ WILL RESIDE ACROSS NRN NEW ENGLAND INTO THE ADIRONDACKS
   WHERE A MIXTURE OF SUPERCELLS AND BOWING STRUCTURES WILL BE
   POSSIBLE.  WHILE VERTICAL SHEAR WILL DECREASE WITH SWD EXTENT ACROSS
   WARM SECTOR...THE DEGREE OF INSTABILITY WILL SUPPORT ORGANIZED
   MULTICELL CLUSTERS AND LINE SEGMENTS.  DAMAGING WINDS WILL BE THE
   PRIMARY SEVERE WEATHER HAZARD...THOUGH A TORNADO OR TWO IS POSSIBLE
   OVER NRN NEW ENGLAND WHERE LOW-LEVEL SHEAR WILL BE THE STRONGEST.

   FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 1871.

   ...MIDWEST TO CNTRL HIGH PLAINS THIS AFTERNOON AND EVENING...

   CONVERGENCE/UPLIFT ALONG THE COLD FRONT WILL PROMOTE WIDELY
   SCATTERED TSTMS THIS AFTERNOON WITHIN A HOT...STEEP-LAPSE-RATE
   BOUNDARY LAYER WHERE MLCAPE WILL APPROACH 1000-2000 J/KG.  ISOLATED
   OCCURRENCES OF DAMAGING WINDS WILL BE POSSIBLE WITH GENERALLY WEAK
   MIDLEVEL LAPSE RATES AND VERTICAL SHEAR PRECLUDING ORGANIZED SEVERE
   WEATHER POTENTIAL.

   ..MEAD/JEWELL.. 09/11/2013

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