Aug 13, 2011 0600 UTC Day 1 Convective Outlook
Updated: Sat Aug 13 05:46:24 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110813 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110813 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
20110813 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
20110813 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.
   SPC AC 130542
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1242 AM CDT SAT AUG 13 2011
   
   VALID 131200Z - 141200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS CNTRL GREAT LAKES/MIDWEST/OH
   VLY REGIONS...
   
   ...SYNOPSIS...
   AN UPR LOW/TROUGH AMPLIFYING OVER THE UPR MIDWEST EARLY SATURDAY
   WILL DIG INTO THE GREAT LAKES AND OH VLY REGIONS BY SATURDAY NIGHT. 
   AT THE BASE OF THE TROUGH...SVRL MCV/S WILL TRAVEL ESE FROM THE SRN
   PLAINS/OZARKS INTO THE MID/DEEP-SOUTH.  IN THE LWR-LVLS...THE SFC
   LOW TIED TO THE STRONGER WAVE WILL DEVELOP EWD FROM MN/WI INTO LWR
   MI DURING THE AFTN.  SEGMENTED COLD FRONT/WIND SHIFTS WILL SETTLE
   SEWD THROUGH THE MIDWEST AND OH/MID-MS VLYS AND BE IMPETUS FOR PSBL
   ORGANIZED SVR STORMS.  TO THE S...A SERIES OF OUTFLOW BOUNDARIES/OLD
   FRONT WILL EXIST FROM PARTS OF THE RED RVR VLY SEWD INTO THE DEEP S.
   
   
   ...CNTRL GREAT LAKES/MIDWEST/OH VLY REGIONS...
   THERE WILL LIKELY BE ONGOING CLOUDS/CONVECTION EARLY IN THE PD
   ACROSS THE GREAT LAKES REGION...TIED TO A WEAK LEAD MID-LVL WAVE
   MOVING ACROSS LWR MI.  PASSAGE OF THIS IMPULSE WILL RESULT IN A
   DECIDEDLY VEERED WSW LLVL FLOW REGIME AHEAD OF THE STRONGER WAVE
   OVER THE UPR MS VLY.  WHILE THIS WILL LIMIT OVERALL MASS
   CONVERGENCE...FLOW REGIME WILL TRANSPORT LWR 60S SFC DEW POINTS FROM
   THE CNTRL PLAINS NEWD INTO THE MIDWEST.  COOLING MID-LVL TEMPS AND
   REASONABLY MOIST BOUNDARY LAYER WILL YIELD 1000-2000 J/KG MLCAPE BY
   AFTN FROM IL NEWD INTO SERN LWR MI.
   
   CONVECTION MAY FESTER ALL DAY IN LWR MI...LIMITING NWD EXTENT OF
   STRONGER THERMAL BUOYANCY.  HOWEVER...PRESENCE OF THE SFC LOW/WEAK
   TURNING IN LOWEST 1-2KM AND POCKETS OF HEATING PSBL...BRIEF
   ORGANIZED STORMS MAY RESULT IN DMGG WIND GUSTS AND PERHAPS A TORNADO
   ACROSS LWR MI.  THE STRONGER THREATS OF SVR STORMS WILL DEVELOP
   MID-AFTN ONWARD IN NRN/CNTRL PARTS OF IL/IND IN COMPARATIVELY
   STRONGER CAPE AND AS LARGER-SCALE FORCING ARRIVES.  THE REGION WILL
   BE ALONG/N OF A 40-45 KT WLY MID-LVL JET WITH FAVORABLE SHEAR TO
   SUPPORT BOTH BOWS AND SUPERCELLS WITH SVR WINDS/HAIL.  ACTIVITY WILL
   BACKBUILD SWWD INTO THE LWR OH AND PSBLY THE MID-MS VLYS DURING THE
   LATE AFTN AND ADVANCE SEWD TOWARD SRN OH/KY DURING THE EVE WITH A
   CONTINUED HIGH WIND THREAT.
   
   ...MID/DEEP-SOUTH...
   LOW CONFIDENCE FCST EXISTS FOR SATURDAY.  ONE OR MORE MCV/S WILL
   LIKELY EVOLVE FROM CURRENT STORMS OVER THE MID-SOUTH/SRN PLAINS. 
   THESE WILL GENERALLY TRACK ESE TOWARD THE MID/DEEP-SOUTH DURING PEAK
   HEATING.  THERE WILL BE SOME INCREASE IN NWLY MID-LVL FLOW ALONG THE
   BASE OF THE MIDWEST UPR TROUGH...ALONG WITH SPEED MAXIMA ASSOCIATED
   WITH THE MCV/S.  STRONGEST HEATING WILL TAKE PLACE OVER N TX EWD
   INTO NRN LA AND DELTA REGION OF MS AND STORMS MAY REKINDLE ALONG
   OUTFLOW BOUNDARIES AND PROPAGATE ESE.  AT LEAST ISOLD STORMS MAY
   POSE A DMGG WIND RISK...ALTHOUGH COVERAGE IS IN QUESTION.  LATER
   OTLKS WILL ADDRESS SHORT-TERM TRENDS AND PSBLY AN UPGRADE TO
   CATEGORICAL SLGT RISK.
   
   ...NC NWD INTO CNTRL PA/NY...
   LEAD MID-LVL WAVE/PV-FILAMENT WILL MOVE EWD ACROSS THE UPR OH
   VLY/CNTRL-NRN APPALACHIANS SATURDAY AFTN.  IN ADVANCE OF THIS
   FEATURE...PWAT VALUES OF 1.5-1.75 WILL SURGE NWD ALONG THE
   MOUNTAINS/COASTAL PLAINS.  TSTMS WILL READILY FORM ALONG THE HIGHER
   TERRAIN FROM NC NWD INTO SRN NY.  ISOLD STORMS MAY BRIEFLY ORGANIZE
   /ISOLD DMGG WIND GUSTS/ GIVEN WLY DEEP-LAYER SHEAR INCREASING TO
   30-35 KTS...PARTICULARLY ALONG/N OF THE MASON-DIXON LINE.  STORMS
   WILL MOVE ONTO THE COASTAL PLAINS DURING THE EVENING...WITH PERHAPS
   A LINGERING THREAT FOR GUSTY WINDS.
   
   ..RACY/LEITMAN.. 08/13/2011
   
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