Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 261233
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 AM CDT THU JUN 26 2008
   
   VALID 261300Z - 271200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF SRN ND...SD..NERN
   NEB..SWRN MN..CENTRAL/NWRN IA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE CORRIDOR FROM
   THE NRN/CENTRAL HIGH PLAINS EWD INTO THE SRN GREAT LAKES REGION...
   
   ...NRN/CENTRAL PLAINS...
   SURFACE PATTERN REMAINS QUITE COMPLEX EARLY THIS MORNING DUE TO
   SEVERAL OUTFLOW BOUNDARIES FROM PRIOR CONVECTION...REINFORCED BY
   ONGOING COMPLEXES OVER THE LOWER/MID MO RIVER VALLEY.  EXPECT MCS
   OVER MO WILL CONTINUE WEAKENING THIS MORNING...WHILE ONE OR MORE
   COMPLEXES EVOLVE ACROSS SRN/ERN SD-NEB TRACKING GENERALLY ESEWD INTO
   IA/NRN MO/SRN MN THROUGH THE DAY AHEAD OF LOW AMPLITUDE SHORTWAVE
   TROUGH.  SURFACE LAYER AHEAD OF THIS ACTIVITY WILL LIKELY REMAIN
   FAIRLY STABLE FOR MUCH OF THE DAY IN WAKE OF EXTENSIVE OUTFLOW
   BOUNDARY EXTENDING FROM E-CENTRAL MO INTO NERN NEB AT 12Z. 
   HOWEVER...FEED OF VERY UNSTABLE ELEVATED PARCELS WITHIN NERN
   PERIPHERY OF STEEP MID LEVEL LAPSE RATES SHOULD SUSTAIN A RISK OF
   LARGE HAIL AND ISOLATED DAMAGING WINDS.  SURFACE BASED THREAT WILL
   INCREASE WITH ANY STORM REMAINING ANCHORED NEAR OUTFLOW BOUNDARY
   OVER WRN/CENTRAL IA/NRN MO.
   
   MORE ACTIVE/INTENSE DEVELOPMENT IS EXPECTED TO OCCUR LATER TODAY AND
   FARTHER TO THE NORTHWEST AS ANOTHER SHORTWAVE TROUGH SHIFTS ACROSS
   THE NRN HIGH PLAINS.  EFFECTS OF EARLY DAY STORMS AND STRONG CAPPING
   SHOULD LIMIT ACTIVITY FOR MUCH OF THE DAY IN WAKE OF MORNING STORMS.
    ALTHOUGH MODELS AGREE IN INCREASING SLY LOW LEVEL FLOW ACROSS THE
   WRN DAKOTAS AHEAD OF APPROACHING WAVE...SUGGESTING SURFACE
   RECOVERY/MOISTURE INFLUX SHOULD SPREAD OUT OF THE CENTRAL PLAINS
   INTO THIS REGION DURING THE AFTERNOON.  MODELS INDICATE EXTREME
   INSTABILITY AND MID-UPPER 60F SURFACE DEW POINTS WILL BE IN PLACE SD
   AND POSSIBLY PORTIONS OF SRN/WRN ND BY 21-00Z.  HOWEVER...THIS
   REMAINS QUESTIONABLE TO SOME DEGREE GIVEN AMOUNT OF RECOVERY WHICH
   NEEDS TO OCCUR.  REGARDLESS...AS MASS FIELDS RESPOND TO APPROACHING
   HEIGHT FALLS ALOFT...EXPECT NWWD EXTENSION OF RICH
   MOISTURE/INSTABILITY AXIS INTO WRN-CENTRAL SD/SWRN ND BY LATE TODAY.
    THIS SHOULD RESULT IN A ESE-WNW AXIS OF VERY STRONG INSTABILITY
   FROM THE LOWER MO/MID MS RIVER VALLEYS TOWARDS SWRN ND.
   
   OVERALL SCENARIO OF EXPECTED SEVERE EVENT DIFFICULT TO NAIL DOWN AT
   THIS JUNCTURE GIVEN UNCERTAINTIES MENTIONED ABOVE.  HOWEVER...
   COMBINATION OF EXTREME INSTABILITY...35-45 KT EFFECTIVE SHEAR AND
   APPROACHING SHORTWAVE TROUGH SHOULD SUPPORT WIDESPREAD SEVERE
   THUNDERSTORMS /SOME SIGNIFICANT/...ESPECIALLY DURING LATTER HALF OF
   THE PERIOD ALONG/AHEAD OF DEVELOPING SURFACE COLD FRONT.  STORMS
   WILL OCCUR IN MULTIPLE MODES...INCLUDING SUPERCELLS...AND MAY EVOLVE
   INTO A LARGER SEVERE COMPLEX /POSSIBLE DERECHO/ MOVING ESEWD ALONG
   INSTABILITY GRADIENT ACROSS MUCH OF MDT RISK AREA LATER THIS
   EVENING/OVERNIGHT.  SIGNIFICANT/DAMAGING HAIL CAN BE EXPECTED WITH
   ANY PERSISTENT SUPERCELL...ALONG WITH POTENTIAL FOR ISOLATED
   TORNADOES.  DAMAGING WIND POTENTIAL IS ALSO EXPECTED TO INCREASE
   LATER TODAY AND TONIGHT.
   
   ...CENTRAL HIGH PLAINS SWD INTO THE SRN HIGH PLAINS...
   WV IMAGERY DEPICTS SLOW MOVING IMPULSE MOVING ACROSS NM THIS
   MORNING.  THIS SHOULD INCREASE THUNDERSTORMS EWD ACROSS THE CENTRAL
   HIGH PLAINS LATER TODAY WHERE DEEPLY MIXED AND VERY WARM BOUNDARY
   LAYER WILL SUPPORT THREATS OF DAMAGING WINDS AND ISOLATED LARGE HAIL
   THROUGH THE MID EVENING...DESPITE ONLY MODEST DEEP LAYER SHEAR.
   
   ...MID MS RIVER VALLEY ACROSS THE SRN/ERN GREAT LAKES...
   CONVECTIVELY ENHANCED VORT CENTER NOW OVER CENTRAL IL WILL CONTINUE
   SLOWLY EWD TODAY...WHERE LARGE AREA OF MODERATE INSTABILITY SHOULD
   DEVELOP OVER THE SRN GREAT LAKES REGION.  ASSOCIATED INCREASE IN MID
   LEVEL WSWLY FLOW AND ASCENT ARE EXPECTED TO INCREASE THREATS OF
   LARGE HAIL/DAMAGING WINDS BY THE EARLY AFTERNOON THUNDERSTORMS
   DEVELOP INTO NRN IND/SWRN MI/OH.  SCATTERED THUNDERSTORMS ARE ALSO
   EXPECTED WITHIN MODEST INSTABILITY INTO THE UPPER OH RIVER VALLEY
   INTO WRN PA/NY TODAY...IN WAKE OF MORNING CLOUDS/SHALLOW CONVECTION.
    FOCUS FOR ACTIVITY WILL BE DIFFUSE...HOWEVER SUFFICIENT SHEAR
   /20-30 KT DEEP LAYER SHEAR/ WILL BE IN PLACE TO MAINTAIN A RISK OF
   LARGE HAIL/DAMAGING WINDS ACROSS THIS REGION.
   
   ...NEW ENGLAND...
   EXTENSIVE AREA OF SHALLOW CONVECTION ASSOCIATED WITH LOW AMPLITUDE
   SHORTWAVE TROUGH WILL OVERSPREAD THE REGION EARLY TODAY AND INHIBIT
   MUCH IN THE WAY OF DESTABILIZATION.  ALTHOUGH RESIDUAL LOW LEVEL
   MOISTURE /SURFACE DEW POINTS NEAR 60F/ SHOULD SUPPORT WEAK
   INSTABILITY WITH DIURNAL HEATING...OVERALL SEVERE THREAT SHOULD BE
   LIMITED TO MARGINAL HAIL/WIND WITH STRONGER STORMS.
   
   ...SERN CONUS/GULF COAST STATES...
   SCATTERED TO LOCALLY NUMEROUS TSTMS WILL DEVELOP ONCE AGAIN ACROSS
   THIS REGION DURING PEAK HEATING.  WEAK AMBIENT SHEAR WILL LIMIT
   ORGANIZED SVR POTENTIAL...HOWEVER RATHER BROAD AREA OF MRGL THREAT
   EXISTS WHERE LOCALIZED PULSE/MULTICELL ORIGINATED DOWNBURSTS MAY
   CAUSE DAMAGE.  ACTIVITY SHOULD UNDERGO NET DECREASE DURING EVENING
   AS COMBINATION OF EXPANDING OUTFLOW AIR AND LOSS OF DIABATIC SFC
   HEATING COMBINE TO REDUCE BUOYANCY.
   
   ..EVANS/SMITH.. 06/26/2008
   
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