May 9, 2011 0600 UTC Day 1 Convective Outlook
Updated: Mon May 9 06:03:08 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110509 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110509 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
20110509 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
20110509 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 090559
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 AM CDT MON MAY 09 2011
   
   VALID 091200Z - 101200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
   PLAINS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN IA...SW WI
   AND IL...
   
   ...NRN PLAINS/NRN HIGH PLAINS...
   AN UPPER-LEVEL LOW OVER THE WRN STATES WILL MOVE SWD TODAY AS A 60
   TO 75 KT MID-LEVEL JET ROUNDS THE BASE OF THE TROUGH. THE EXIT
   REGION OF THE MID-LEVEL JET IS FORECAST TO OVERSPREAD THE NRN PLAINS
   BY EARLY THIS EVENING HELPING TO ENHANCE SHEAR PROFILES ACROSS THE
   REGION. THIS WILL HELP CREATE CONDITIONS FAVORABLE FOR STRONG
   THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THE ECMWF...GFS AND NAM-KF
   ARE IN REASONABLE AGREEMENT...INITIATING A CLUSTER OF THUNDERSTORMS
   AROUND RAPID CITY AT 00Z AND MOVING THIS CONVECTION NEWD INTO CNTRL
   AND NRN SD DURING THE EVENING.
   
   FORECAST SOUNDINGS ACROSS THE SOUTH DAKOTA AT 00Z TO 03Z SHOW MLCAPE
   VALUES RANGING FROM AROUND 1000 J/KG IN SWRN SD TO AROUND 3000 J/KG
   IN ERN SD WITH 0-6 KM SHEAR VALUES ACROSS SD IN THE 30 TO 40 KT
   RANGE. THIS ALONG WITH STEEP MID-LEVEL LAPSE RATES SHOULD BE
   SUPPORTIVE OF LARGE HAIL WITH STORMS THAT HAVE ACCESS TO THE
   STRONGER INSTABILITY. THE NAM IS THE OUTLIER DRIVING THE COLD FRONT
   ACROSS WRN SD AND STABILIZING THE AIR MASS AROUND RAPID CITY. THIS
   INTRODUCES UNCERTAINTY INTO THE FORECAST BUT AM FAVORING THE NAM-KF
   WHICH DEVELOPS MORE INSTABILITY ACROSS CNTRL AND WRN SD. AT THIS
   POINT...WILL MAINTAIN A SMALL 30 PERCENT PROBABILITY FOR LARGE HAIL
   IN CNTRL SD WHERE CONFIDENCE IS THE GREATEST CONCERNING MODERATE TO
   STRONG DESTABILIZATION. IF SUPERCELLS CAN DEVELOP IN CNTRL SD...THEN
   AN ISOLATED THREAT FOR TORNADOES OR VERY LARGE HAIL COULD ALSO
   EXIST. A WIND DAMAGE THREAT MAY ALSO DEVELOP BUT MAY BE FOCUSED
   DURING THE MID TO LATE EVENING HOURS IF A LINE OF STORMS CAN
   ORGANIZE ACROSS THE REGION.
   
   ...ERN IOWA/ILLINOIS/SW WISCONSIN...
   SOUTHWEST FLOW WILL BE IN PLACE ACROSS THE MID TO UPPER MS VALLEY
   JUST TO THE WEST OF AN UPPER-LEVEL RIDGE IN THE WRN GREAT LAKES AND
   LOWER OH VALLEY. BENEATH THE SOUTHWEST FLOW...A BROAD LOW-LEVEL JET
   SHOULD EXIST FROM THE OZARKS NWD INTO THE UPPER MS VALLEY. WARM
   ADVECTION ASSOCIATED WITH THE LOW-LEVEL JET SHOULD MOVE THE
   INSTABILITY AXIS QUICKLY NWD INTO ERN IA AND IL THIS AFTERNOON.
   THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG THE INSTABILITY
   GRADIENT LATE THIS AFTERNOON IN ERN IA...SRN WI AND IL WHERE
   FORECAST SOUNDINGS SHOW FAVORABLE SHEAR PROFILES FOR SEVERE STORMS.
   HOWEVER...A CAPPING INVERSION IS FORECAST TO BE IN PLACE ACROSS THE
   WARM SECTOR SUGGESTING STORMS WILL HAVE TROUBLE INITIATING SOUTH OF
   THE WARM FRONT WHERE THE MOST FAVORABLE ENVIRONMENT IS FORECAST. IF
   CONVECTION CAN INITIATE NEAR THE WARM FRONT WHERE MODERATE
   INSTABILITY SHOULD EXIST...THEN SUPERCELL DEVELOPMENT WILL BE
   POSSIBLE WITH A THREAT FOR ISOLATED LARGE HAIL AND WIND DAMAGE. THIS
   THREAT MAY INCREASE DURING THE EVENING AND OVERNIGHT PERIOD AS THE
   LOW-LEVEL JET STRENGTHENS ACROSS THE REGION AND DESTABILIZATION
   OCCURS FURTHER NORTH AND EAST ACROSS THE REGION.
   
   ...ERN GULF COAST STATES/FLORIDA...
   NORTHWEST FLOW WILL BE IN PLACE FROM THE SRN APPALACHIAN MTNS SEWD
   ACROSS THE ERN GULF COAST STATES. AS SFC TEMPS HEAT UP THIS
   AFTERNOON...ISOLATED THUNDERSTORMS SHOULD INITIATE ALONG AN AXIS OF
   MODERATE INSTABILITY IN THE HIGHER TERRAN OF THE SRN APPALACHIAN
   MTNS AND ACROSS THE COASTAL PLAINS OF ERN GA AND NRN FL. FORECAST
   SOUNDINGS ALONG THIS CORRIDOR AT 21Z TO 00Z SUGGEST MLCAPE VALUES
   WILL BE IN THE 1500 TO 2000 J/KG RANGE WITH 0-6 KM SHEAR VALUES
   AROUND 30 KT. THIS ENVIRONMENT COULD SUPPORT A MARGINAL SEVERE
   THREAT WITH EITHER HAIL AND/OR STRONG GUSTY WINDS POSSIBLE WITH THE
   MORE INTENSE CELLS.
   
   ..BROYLES/STOPKOTTE.. 05/09/2011
   
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