Categorical Graphic
Probabilistic Tornado 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
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
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 041953
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0253 PM CDT FRI MAY 04 2012
   
   VALID 042000Z - 051200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
   PLAINS...CNTRL PLAINS...UPPER MS VALLEY...OH VALLEY...CNTRL
   APPALACHIAN MTNS AND MID-ATLANTIC...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN PLAINS...
   
   A FEW CHANGES HAVE BEEN MADE TO THE OUTLOOK AT 20Z. THE FIRST IS TO
   REMOVE THE SLIGHT RISK FROM PARTS OF NE AND CNTRL SD WHERE
   INSTABILITY IS VERY WEAK IN THE WAKE OF CONVECTION MOVING EWD INTO
   THE SW MN. THE SECOND CHANGE IS TO EXTEND THE 5 PERCENT TORNADO
   PROBABILITY EWD ACROSS FAR SRN MN AND NRN IA ALONG THE PROJECTED
   TRACK OF A SUPERCELL CURRENTLY JUST NORTH OF THE MN-IA STATELINE.
   THE THIRD CHANGE TO THE OUTLOOK IS TO MAKE THE 30 PERCENT WIND
   DAMAGE PROBABILITY IN SRN IND AND WRN KY SMALLER AND LOCATED JUST
   AHEAD OF A BOWING LINE-SEGMENT CURRENTLY IN SRN IND.
   
   ..BROYLES.. 05/04/2012
   
   .PREV DISCUSSION... /ISSUED 1128 AM CDT FRI MAY 04 2012/
   
   ...SYNOPSIS...
   
   MOST PROMINENT LARGE-SCALE FEATURE THIS PERIOD IS MIDLEVEL TROUGH
   WHICH WILL UNDERGO AMPLIFICATION WHILE PROGRESSING FROM THE PACIFIC
   NW INTO NRN INTERMOUNTAIN REGION.  THIS FEATURE WILL BE EMBEDDED
   WITHIN THE PRIMARY BELT OF WESTERLIES EXTENDING EWD ACROSS THE
   N-CNTRL STATES TO A DOWNSTREAM TROUGH MOVING SEWD THROUGH QUEBEC AND
   NEW ENGLAND.  ELSEWHERE...A LOWER LATITUDE BELT OF HIGHER MOMENTUM
   FLOW WITH EMBEDDED VORTICITY MAXIMA --SOME OF CONVECTIVE ORIGIN--
   WILL EXIST FROM THE SRN PLAINS THROUGH MID-MS AND OH VALLEYS TO
   MID-ATLANTIC COAST.
   
   AT THE SURFACE...MORNING ANALYSIS SHOWS PRIMARY SYNOPTIC FRONT
   EXTENDING FROM THE LOWER GREAT LAKES WWD THROUGH THE MID-MO VALLEY
   TO LOW PRESSURE OVER SWRN NEB...AND THEN NNWWD INTO ERN MT.  THE ERN
   EXTENSION OF THIS BOUNDARY WILL ADVANCE EWD/SEWD THROUGH THE NERN
   STATES IN CONJUNCTION WITH THE ABOVE-MENTIONED SHORTWAVE TROUGH. 
   LITTLE NET SWD DISPLACEMENT OF THE FRONT IS ANTICIPATED OVER THE
   NRN/CNTRL PLAINS OWING TO FALLING HEIGHTS/PRESSURES ASSOCIATED WITH
   PRIMARY MIDLEVEL TROUGH MOVING INTO THE NRN ROCKIES.  THIS SYNOPTIC
   FRONT AND PRE-EXISTING CONVECTIVE OUTFLOW BOUNDARIES OVER THE OH AND
   MID-MS VALLEYS WILL LIKELY SERVE AS THE FOCI FOR STRONG-SEVERE TSTM
   DEVELOPMENT THIS AFTERNOON INTO TONIGHT.
   
   ...NRN/CNTRL PLAINS INTO MID-MS VALLEY THIS AFTERNOON THROUGH
   TONIGHT...
   
   CLUSTERS OF ELEVATED TSTMS ARE ONGOING OVER SD AND ERN MO...WITH
   ACTIVITY LARGELY BEING FORCED BY LOWER TO MID-TROPOSPHERIC WAA
   ASSOCIATED WITH A MULTI-BRANCHED NOCTURNAL LLJ.  THE DIURNAL
   CESSATION OF THIS FEATURE ALONG WITH WEAK MIDLEVEL HEIGHT RISES
   ACROSS THE REGION TODAY CAST SOME UNCERTAINTY AS TO WHETHER CURRENT
   STORMS WILL RE-INTENSIFY BY LATE MORNING INTO AFTERNOON.  DESPITE
   THE GRADUAL WEAKENING OF LARGE-SCALE FORCING FOR ASCENT...12Z
   SOUNDINGS FROM THE CENTRAL PLAINS INTO OZARKS SHOWED THE PRESENCE OF
   A MOIST BOUNDARY LAYER /I.E. LOWEST 100-MB MEAN MIXING RATIOS OF
   11-15 G PER KG/ BENEATH A PLUME OF STEEP MIDLEVEL LAPSE RATES
   /7.5-9.0 C PER KM/...WHICH WILL YIELD MODERATE-STRONG AFTERNOON
   INSTABILITY ALONG/S OF SYNOPTIC BOUNDARY.
   
   THOUGH SCENARIO REMAINS UNCLEAR...SEVERE WEATHER POTENTIAL WILL
   INCREASE THIS AFTERNOON INTO EVENING EITHER WITH THE
   RE-INTENSIFICATION OF ONGOING STORMS AND/OR NEW TSTM DEVELOPMENT
   ALONG SYNOPTIC FRONT AND CONVECTIVE OUTFLOW BOUNDARIES.  THE
   STRONGEST LOW- AND DEEP-LAYER SHEAR IS FORECAST ACROSS SD/NEB INTO
   MN/IA WHERE SUPERCELLS CAPABLE OF DAMAGING WINDS...LARGE HAIL AND A
   FEW TORNADOES ARE POSSIBLE.  ELSEWHERE...THE MODERATE-STRONG
   INSTABILITY AND MODEST DEEP-LAYER FLOW WILL FOSTER A MIX OF
   MULTICELL AND SUPERCELL/BOWING STRUCTURES CAPABLE OF MAINLY DAMAGING
   WINDS AND LARGE HAIL.
   
   ...OH VALLEY TO MID-ATLANTIC COAST THIS AFTERNOON INTO TONIGHT...
   
   MORNING VISIBLE SATELLITE AND RADAR DATA SHOW A SERIES OF
   CONVECTIVELY INDUCED VORTICITY MAXIMA PROGRESSING EWD ACROSS THE
   REGION.  FORCING ASSOCIATED WITH THESE FEATURES...SEWD-PROGRESSING
   COLD FRONT...LEE TROUGH...AND PRE-EXISTING CONVECTIVE OUTFLOW
   BOUNDARIES WILL FOCUS AN INCREASE IN TSTM DEVELOPMENT TODAY WITHIN
   AN MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000+ J/KG.  THE
   STRONGEST DEEP-LAYER SHEAR WILL EXIST ACROSS THE OH VALLEY WHERE
   ENVIRONMENT WILL SUPPORT SUPERCELL AND/OR BOWING STRUCTURES CAPABLE
   OF LARGE HAIL AND DAMAGING WINDS.  FARTHER E...WEAKER VERTICAL SHEAR
   WILL MODULATE THE DEGREE OF STORM ORGANIZATION WITH MULTICELL AND
   PULSE STORM MODES WITH A RISK FOR DAMAGING WINDS AND PERHAPS SOME
   HAIL.
   
   ...SRN PLAINS THIS AFTERNOON INTO TONIGHT...
   
   12Z OUN/FWD SOUNDINGS SHOWED 8.0-9.0 C/KM 700-500-MB LAPSE RATES
   ATOP 100-MB LOWEST-MEAN MIXING RATIOS OF 14-15 G/KG WHICH WILL
   COMBINE WITH DAYTIME HEATING TO YIELD A VERY UNSTABLE AIR MASS BY
   AFTERNOON.  FORCING FOR ASCENT ATTENDANT TO SHORTWAVE TROUGH MOVING
   NEWD ACROSS AREA WILL COMBINE WITH A DEEPENING DRYLINE CIRCULATION
   TO FOSTER ISOLATED-WIDELY SCATTERED SURFACE-BASED TSTM DEVELOPMENT
   BY AFTERNOON FROM SWRN TX INTO CNTRL/ERN OK.  THE DEGREE OF
   INSTABILITY WILL COMPENSATE FOR MARGINALLY STRONG VERTICAL SHEAR TO
   PROMOTE MULTI- AND SUPERCELL STORM MODES WITH THE PRIMARY HAZARD
   BEING LARGE HAIL.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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