Aug 13, 2011 1630 UTC Day 1 Convective Outlook
Updated: Sat Aug 13 16:28:10 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110813 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110813 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
20110813 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
20110813 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.
   SPC AC 131623
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1123 AM CDT SAT AUG 13 2011
   
   VALID 131630Z - 141200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS IL EWD INTO SRN LOWER MI/WRN OH
   AND SEWD INTO FAR NWRN KY...
   
   ...SYNOPSIS...
   SATELLITE AND RADAR SHOWED A PROGRESSIVE SHORTWAVE TROUGH MOVING
   ESEWD THROUGH NERN IA AT MID MORNING...WHICH IS FORECAST TO MOVE EWD
   INTO THE FAR NRN UPPER OH VALLEY BY EARLY SUNDAY. THIS WILL RESULT
   IN LOWERING HEIGHTS AND STRENGTHENING WIND FIELDS OVER THE ERN HALF
   OF THE CONUS...AS THE UPPER RIDGE BUILDS NWD ACROSS THE ROCKIES. AT
   THE SURFACE...A WEAK SURFACE LOW WAS LOCATED IN SRN WI WITH A WEAK
   FRONT STRETCHING SWWD THROUGH MO...INTO NRN OK AND ERN NM. WHILE
   STORMS ARE EXPECTED ALONG THE FRONT FROM IL EWD THIS AFTERNOON AND
   EVENING...THE SRN PORTION OF THE FRONT WILL CONTINUE TO SHIFT SEWD
   THROUGH AN AIR MASS THAT WAS OVERTURNED BY OVERNIGHT
   CONVECTION...REFERENCE 12Z OKC/SGF/LIT SOUNDINGS. THIS SHOULD LIMIT
   STRONG CONVECTIVE DEVELOPMENT ALONG THIS PORTION OF THE
   FRONT...THOUGH ISOLATED STRONG STORMS ARE POSSIBLE NEAR BOUNDARIES
   LOCATED WELL SOUTH AND EAST OF THE FRONT.
   
   ...IL EWD INTO SRN LOWER MI/WRN OH AND SEWD INTO FAR NWRN KY...
   A FEW STORMS WERE ALREADY ONGOING NEAR SURFACE LOW EWD INTO SRN
   LOWER MI. STORMS SHOULD SLOWLY INTENSIFY THROUGH THE DAY AS LARGE
   SCALE FORCING SPREADS EWD...COMBINED WITH COOLING ALOFT...500 MB
   TEMPERATURES FROM -12C TO -14C...AND STRONG HEATING. GIVEN DEEP
   TROPOSPHERIC UNIDIRECTIONAL WLY FLOW ALOFT AND 35-40 KT MID LEVEL
   WINDS...ENVIRONMENT APPEARS FAVORABLE FOR STORMS TO ORGANIZE INTO
   LINE SEGMENTS/EMBEDDED BOWS. ACROSS NRN HALF OF SLIGHT RISK...
   SLIGHTLY STRONGER LOW/DEEP LAYER SHEAR MAY SUPPORT A FEW SUPERCELLS
   WITH MARGINALLY SEVERE HAIL. ONCE A LINE DEVELOPS...
   IT SHOULD MOVE SEWD AT 25-30KT...AND EVEN FASTER IF A COLD POOL
   DEVELOPS. STORMS ARE EXPECTED TO WEAKEN DURING THE EVENING WITH LOSS
   OF BOUNDARY LAYER INSTABILITY.
   
   ...ERN TX NEWD INTO NRN AL/MIDDLE TN...
   CONSIDERABLE CLOUD COVER AND WEAKENING CLUSTERS OF CONVECTION WERE
   LOCATED OVER THE REGION THIS MORNING. WHERE STRONGER
   HEATING/MODERATE INSTABILITY OCCURS...WIDELY SCATTERED SURFACE BASED
   STORMS MAY DEVELOP ON REMNANT OUTFLOW BOUNDARIES. HOWEVER...WEAK
   FORCING AND EFFECTIVE SHEAR AT 10 TO 20 KT INDICATE THAT THE THREAT
   FOR MORE THAN ISOLATED WIND DAMAGE IS LOW.
   
   ...NC NWD INTO CNTRL PA/NY...
   SCATTERED STORMS WERE OCCURRING FROM SC NWD INTO DELMARVA WITHIN
   MOIST AND WEAKLY FORCED ENVIRONMENT...ASSOCIATED WITH CYCLONIC FLOW
   ALOFT AND GRADUAL HEIGHT FALLS. DEEP LAYER SHEAR AT 20-30 KT MAY
   BRIEFLY ORGANIZE A FEW STORMS WITH ISOLATED GUSTY WINDS.
   HOWEVER...MOIST ADIABATIC LAPSE RATES COMBINED WITH MOSTLY CLOUDY
   SKIES/SCATTERED/NUMEROUS STORMS SHOULD LIMIT POTENTIAL FOR A MORE
   WIDESPREAD DAMAGING WIND THREAT.
   
   ..IMY/COHEN.. 08/13/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z