Sep 5, 2012 1300 UTC Day 1 Convective Outlook
Updated: Wed Sep 5 13:01:29 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120905 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120905 1300 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
20120905 1300 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
20120905 1300 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 051257
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0757 AM CDT WED SEP 05 2012
   
   VALID 051300Z - 061200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES ACROSS THE
   MIDWEST TO LOWER/MID MS VALLEY...
   
   ...GREAT LAKES/MIDWEST...
   A STRONG SHORTWAVE TROUGH WITH 12H 500MB HEIGHT FALLS AROUND 60M
   CROSSED MN OVERNIGHT AS AN ASSOCIATED COLD FRONT USHERED IN A COOLER
   AND DRIER AIRMASS ACROSS THE NRN/CNTRL PLAINS. WELL AHEAD OF THE
   WIND SHIFT ACCOMPANYING THE COLD FRONT...FROM THE GREAT LAKES TO
   MIDWEST...SCATTERED TSTMS WERE OCCURRING IN THE EXTENSIVE
   PRE-FRONTAL WARM SECTOR. THE MOST ORGANIZED/PERSISTENT STORMS
   OVERNIGHT WERE ASSOCIATED WITH THE NOW WEAKENING MCS MOVING ACROSS
   NRN IL. WHILE STRONGER ASCENT/FORCING WITH THE SHORTWAVE TROUGH OVER
   MN WILL LIFT INTO CANADA TODAY...WEAK HEIGHT FALLS AND STRENGTHENING
   DEEP-LAYER W-NWLY FLOW WILL ACCOMPANY THE COLD FRONT AS IT ADVANCES
   EAST TO THE GREAT LAKES/UPPER MIDWEST...COINCIDENT WITH DIURNAL
   HEATING AND DESTABILIZATION.
   
   THE FORECAST IS COMPLICATED BY ONGOING CONVECTION...CONVECTIVE
   DEBRIS...AND THE NUMBER OUTFLOW BOUNDARIES EXISTING AHEAD OF THE
   PRIMARY SYNOPTIC FRONT. HOWEVER...EXPECT AT LEAST MODEST AIRMASS
   RECOVERY AND AREAS OF POTENTIALLY STRONG DESTABILIZATION TO OCCUR
   NEAR AND IN THE WAKE OF THE MCS OUTFLOW FROM CNTRL IL WWD ACROSS THE
   MS RIVER TO NRN MO AND ERN IA. MLCAPE IN THESE AREAS SHOULD REACH AT
   LEAST 2000 J/KG BY THIS AFTERNOON AHEAD OF THE ADVANCING COLD FRONT.
   ISENTROPIC LIFT ACROSS THE RESIDUAL COLD POOL AND FORCING NEAR
   OUTFLOW/FRONT INTERSECTION...IN CONCERT WITH WEAK HEIGHT
   FALLS...WILL LIKELY AID NEW TSTM DEVELOPMENT IN THESE AREAS THROUGH
   LATE AFTERNOON. THIS DEVELOPMENT SHOULD OCCUR AS MID LEVEL WINDS AND
   EFFECTIVE SHEAR STRENGTHEN TO SUPPORT ORGANIZED STORMS POSING A
   THREAT OF VERY LARGE HAIL. STORM/BOUNDARY INTERACTIONS COULD ALSO
   RESULT IN LOCALLY ENHANCED TORNADO POTENTIAL BUT ACTIVITY WILL
   EVENTUALLY CONGEAL OR FOCUS ALONG THE ADVANCING FRONT AND SPREAD
   EAST ACROSS IL/IND AREA WITH AN INCREASING CHANCE FOR DAMAGING
   WINDS.
   
   ...SRN PLAINS TO TN/MS...
   ISOLATED TSTMS EXIST NEAR A WEAK/FRACTURED FRONTAL SEGMENT FROM THE
   SRN PLAINS TO TN VALLEY THIS MORNING. A WELL-DEFINED SHORTWAVE
   TROUGH WAS LIKELY ENHANCING ASCENT ALONG/NEAR THIS WEAK FRONT OVER
   MO ATTM. LIFT WITH THIS DISTURBANCE SHOULD SUPPORT ADDITIONAL TSTM
   DEVELOPMENT AS AIRMASS FROM SERN MO ACROSS THE MS RIVER BECOMES
   MODERATELY UNSTABLE THROUGH THE LATE MORNING AND INTO AFTERNOON.
   WHILE SHEAR WILL NOT BE AS STRONG AS FARTHER NORTH...EXPECT
   ORGANIZED/PERSISTENT MULTICELL STORMS POSING SOME HAIL AND WIND
   THREAT ACROSS SRN PORTIONS OF THE SLGT RISK AREA. FORCING ALONG THE
   BOUNDARY WILL BE WEAKER WITH WWD EXTENT INTO THE SRN PLAINS WHERE
   INHIBITION WILL ALSO BE A LIMITING FACTOR FOR MORE WIDESPREAD STORM
   DEVELOPMENT. HOWEVER...ISOLATED STRONGER STORMS APPEAR POSSIBLE FROM
   OK INTO NRN TX WHERE WELL-MIXED BOUNDARY LAYER MAY ENHANCE
   DOWNDRAFTS SUFFICIENT FOR A COUPLE OF WIND EVENTS.
   
   ...NY/LONG ISLAND/MID ATLANTIC...
   AS SFC LOW MOVES ACROSS NEW ENGLAND THE TRAILING FRONT/WIND SHIFT
   WILL PASS ACROSS SRN NEW ENGLAND AND INTO THE MID ATLANTIC TODAY.
   LIFT ALONG THIS TRAILING FRONT WILL COINCIDE WITH AREAS OF WEAK TO
   MODEST DESTABILIZATION FROM LONG ISLAND SOUTH ACROSS DELMARVA. A FEW
   TSTMS OR LINE SEGMENTS COULD PRODUCE STRONG WINDS WITH FRONTAL
   PASSAGE.
   
   ..CARBIN.. 09/05/2012
   
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