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

   SPC AC 260548
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1248 AM CDT THU JUN 26 2008
   
   VALID 261200Z - 271200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS CORRIDOR FROM NRN HIGH PLAINS
   TO PORTIONS NEW ENGLAND...
   
   ...SYNOPSIS...
   PROGRESSIVE NRN STREAM PATTERN TO CONTINUE THROUGH DAY-1.  NRN
   PORTIONS OF POSITIVELY TILTED SHORTWAVE TROUGH -- NOW EVIDENT IN
   MOISTURE CHANNEL IMAGERY FROM INTERIOR PACIFIC NW SWWD OFF NRN CA --
   IS EXPECTED TO MOVE EWD THROUGH MEAN RIDGE POSITION OVER NRN ROCKIES
   EARLY IN PERIOD.  PERTURBATION THEN SHOULD MOVE EWD ACROSS
   DAKOTAS...TO MN BY 27/12Z.  MEANWHILE...ANOTHER/UPSTREAM TROUGH --
   INITIALLY LOCATED OVER NRN BC -- WILL DIG SEWD TO NRN HIGH
   PLAINS...PRECEDED BY BROAD AREA OF HEIGHT FALLS THAT WILL EXTEND EWD
   TO VICINITY WEAKER/LEAD WAVE.  NET WWD DISPLACEMENT OF RIDGING TO
   PACIFIC COAST WILL RESULT.
   
   AT SFC...COLD FRONT IS EXPECTED TO DEVELOP/INTENSIFY EARLY IN PERIOD
   OVER NRN HIGH PLAINS AND ADJACENT CANADIAN HIGH PLAINS...AND MOVE
   SEWD/EWD OVER MUCH OF DAKOTAS...WY AND WRN NEB BY END OF PERIOD. 
   WARM FRONT -- INITIALLY STATIONARY OVER NEB/IA -- SHOULD LIFT NEWD
   ACROSS UPPER MS VALLEY...WITH WEAK/TRIPLE-POINT LOW PERHAPS FORMING
   AT ITS INTERSECTION WITH COLD FRONT LATE IN PERIOD.  AFTERNOON
   DRYLINE SHOULD BECOME EVIDENT FROM WRN KS SSWWD ACROSS VICINITY
   TX/NM BORDER.
   
   ...CENTRAL/NRN PLAINS...
   WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP
   ALONG/AHEAD OF STRENGTHENING COLD FRONT...DURING AFTERNOON OVER ERN
   MT/NERN WY AND WRN DAKOTAS.  STEEP LOW-MIDLEVEL LAPSE RATES WILL BE
   AUGMENTED BY SFC HEATING...JUXTAPOSED WITH SE-NW ALIGNED SFC MOIST
   AXIS EXTENDING ALONG/S OF WARM FRONT FROM SERN SD TO WRN ND. 
   DEEP-LAYER SHEAR PROFILES WILL BE FAVORABLE...ESPECIALLY INVOF WARM
   FRONT WHERE PRONOUNCED VEERING WITH HEIGHT WILL ENLARGE LOW LEVEL
   HODOGRAPHS AND AUGMENT DEEP-LAYER BULK SHEAR.
   INITIAL POTENTIAL FOR SUPERCELLS -- WITH LARGE/DESTRUCTIVE HAIL
   LIKELY AS WELL AS OCCASIONALLY SVR WIND -- SHOULD EVOLVE TO MORE
   PURELY WIND-BASED THREAT AS ACTIVITY SHIFTS EWD ACROSS MT/DAKOTAS
   AND GROWS UPSCALE DURING EVENING/OVERNIGHT HOURS.  SOME SPATIAL
   OVERLAP IS POSSIBLE BETWEEN OVERNIGHT PART OF THIS THREAT OVER SRN
   MN/NWRN IA REGION AND EARLIER MCS POTENTIAL  MENTIONED BELOW. 
   THEREFORE...BROAD AREA OF RELATIVELY MAXIMIZED WIND PROBABILITIES
   ACTUALLY COVERS TWO DISTINCT CONVECTIVE EVENTS.
   
   SOME SUBSET OF THIS AREA MAY REQUIRE CATEGORICAL OUTLOOK UPGRADE
   ONCE MESOSCALE INFLUENCES ON FOCI ARE BETTER SORTED...FOLLOWING
   PRIOR/OVERNIGHT MCS ACTIVITY.
   
   ...UPPER MS VALLEY REGION TO NEW ENGLAND...
   MCS -- ONGOING AT OUTLOOK TIME OVER SRN SD/NRN NEB...MAY PERSIST
   INTO EARLY DAY-1 PERIOD AND DEVELOP MCV THAT...IN TURN...SUPPORTS
   REINVIGORATED CONVECTIVE/SVR POTENTIAL ACROSS PORTIONS IA AND/OR SRN
   MN EWD TOWARD VICINITY LM DURING AFTERNOON/EVENING HOURS.  PRIMARY
   ASSOCIATED SVR CONCERN WILL BE DAMAGING WIND...WITH SECONDARY THREAT
   LARGE HAIL...AND TERTIARY/MRGL RISK OF TORNADOES PRIMARILY
   ASSOCIATED WITH BOW/LEWP CIRCULATIONS.  LOW-MIDLEVEL SHEAR PROFILES
   WILL BE RATHER MEAGER THANKS TO WEAK SPEEDS -- WITH FCST SOUNDINGS
   SHOWING EFFECTIVE SHEARS GENERALLY 25-35 KT.  HOWEVER...FAVORABLE
   STORM-RELATIVE INFLOW IS LIKELY ALONG AND JUST N OF WARM
   FRONT...WHICH SHOULD SERVE AS PRIMARY FOCUS FOR FORWARD PROPAGATION
   OF BULK OF ACTIVITY.  AIR MASS OVER PORTIONS ERN IA WILL HAVE BEEN
   OVERTURNED BY CURRENT COMPLEX MOVING SEWD INTO NERN MO/NWRN IL --
   LEAVING BEHIND TEMPORARY POCKET OF RELATIVELY LOW THETAE. 
   HOWEVER...COMBINATION OF WARM/MOIST ADVECTION IN ITS WAKE...DIURNAL
   HEATING...AND EVAPOTRANSPIRATION FROM BROAD AREAS OF
   PONDED/SATURATED GROUND...SHOULD RENEW THETAE TO LEVELS APCHG THOSE
   IN RELATIVELY UNDISTURBED AIR MASS FARTHER E AND W.  NET RESULT
   SHOULD BE SFC DEW POINTS UPPER 60S TO MID 70S F SUPPORTING MLCAPES
   UP TO 5000 J/KG OVER PORTIONS IA/IL.
   
   BUOYANCY GENERALLY SHOULD WEAKEN GRADUALLY EWD ACROSS GREAT LAKES
   STATES...BUT REMAIN FAVORABLE FOR ORGANIZED SVR ACROSS NRN
   APPALACHIANS AND PERHAPS PORTIONS NEW ENGLAND.  WEAKER...MORE SUBTLE
   PERTURBATIONS IN MID/UPPER FLOW FIELD...INCLUDING RESIDUAL MCV
   MOVING EWD FROM OH...MAY SUPPORT POTENTIAL FOR SCATTERED TSTMS TO
   DEVELOP IN INCREASINGLY UNSTABLE AIR MASS.
   
   ...SERN CONUS...GULF COAST STATES...
   SCATTERED TO LOCALLY NUMEROUS TSTMS ONCE AGAIN SHOULD DEVELOP DURING
   PEAK OF DIURNAL HEATING AND INTO LATE AFTERNOON.  PREFERENCE FOR SVR
   THREAT WILL GO TO MESOBETA SCALE BOUNDARIES -- E.G. OUTFLOWS AND SEA
   BREEZES -- AND THEIR INTERSECTIONS...WHERE CONVERGENCE WILL BE
   MAXIMIZED LOCALLY.  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.
   
   ...SRN HIGH PLAINS...
   TSTM FORMATION IS POSSIBLE ON BOTH SIDES OF DRYLINE...IN ZONES OF
   VERY STG SFC HEATING AND RESULTANT DEEP MIXING OF BOUNDARY LAYER. 
   LARGE HAIL AND STG-SVR DOWNDRAFTS MAY OCCUR WITH MOST INTENSE CELLS.
    WELL-DEFINED TURNING WITH HEIGHT IS FCST ALONG/E OF DRYLINE...BUT
   WITH WEAK FLOW THROUGH MOST OF TROPOSPHERE KEEPING EFFECTIVE SHEAR
   MAGNITUDES AOB 30 KT MOST AREAS.  ATTM...THEREFORE...ORGANIZED SVR
   POTENTIAL APPEARS TOO CONDITIONAL/WEAK TO ASSIGN CATEGORICAL SLGT
   RISK.
   
   ..EDWARDS/SMITH.. 06/26/2008
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z