Day 1 Severe Weather Outlook

...THERE IS AN ENHANCED RISK ACROSS MUCH OF THE OHIO VALLEY...

...SUMMARY...
SCATTERED TO NUMEROUS SEVERE THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING ACROSS MUCH OF THE OHIO VALLEY, AS WELL AS PORTIONS OF THE GREAT LAKES AND MIDWEST. VERY LARGE HAIL AND POTENTIALLY SIGNIFICANT DAMAGING WINDS ARE EXPECTED, AS WELL AS POTENTIAL FOR A FEW TORNADOES. 

...DISCUSSION...
STRONG ZONAL FLOW ALOFT ACROSS THE GREAT LAKES AND OHIO VALLEY CONTINUES TODAY ON THE NORTH SIDE OF A PERSISTENT MID TO UPPER LEVEL RIDGE CENTERED OVER THE SOUTHERN PLAINS. A BROAD SURFACE CYCLONE OVER SOUTHWESTERN QUEBEC THIS MORNING WILL RACE EASTWARD TODAY, WITH A TRAILING COLD FRONT SURGING SOUTHWARD INTO THE MIDWEST AND OHIO VALLEY BY THIS EVENING. AN AREA OF SHOWERS ASSOCIATED WITH THE WARM AIR ADVECTION REGIME ONGOING ACROSS SOUTHERN INDIANA AND OHIO WILL CONTINUE TO SHIFT SOUTHEASTWARD AND DISSIPATE BY MID TO LATE MORNING. A BROAD AREA OF FAIRLY CLEAR SKIES ALREADY NOTED IN ITS WAKE WILL SPREAD ACROSS THE OHIO VALLEY AND SOUTHERN GREAT LAKES REGION THIS MORNING, ALLOWING FOR STRONG SURFACE HEATING FROM THE MID-70S ACROSS WEST PENNSYLVANIA INTO THE MID-80S FURTHER WEST. DESPITE FAIRLY MODEST DEWPOINTS IN THE MID-50S TO LOW-60S, VERY STEEP LOW AND MID-LEVEL LAPSE RATES IN EXCESS OF 8.0 C/KM SHOULD SUPPORT ROBUST DESTABILIZATION WITH MLCAPE VALUES INCREASING TO THE 1500-2500 J/KG RANGE THIS AFTERNOON WITHIN A BROAD CORRIDOR ALONG AND AHEAD OF THE COLD FRONT. FAIRLY STRONG CAPPING CURRENTLY ACROSS THE REGION GRADUALLY ERODES WITH THIS DESTABILIZATION, EVENTUALLY ENOUGH TO ALLOW FOR RAPID CONVECTIVE INITIATION ALONG THE COLD FRONT LATE THIS AFTERNOON BETWEEN 20Z-22Z, WITH SHORTWAVE ENERGY PASSING OVERHEAD DURING THIS TIME. 

VERY STRONG DEEP-LAYER SHEAR IN EXCESS OF 65KT DRIVEN BY THE STRONG MID-LEVEL ZONAL FLOW WILL ALSO BE ENHANCED BY A 45-60KT SOUTHWESTERLY LOW-LEVEL JET DEVELOPING BY LATE AFTERNOON. FAIRLY ENLARGED/ELONGATED AND CURVING HODOGRAPHS WILL INITIALLY FAVOR SUPERCELLS PRODUCING SWATHS OF VERY LARGE HAIL IN EXCESS OF 2 INCHES IN DIAMETER AS WELL AS A THREAT FOR DAMAGING WIND GUSTS. A COUPLE OF TORNADOES MAY ALSO MATERIALIZE DUE TO EFFECTIVE SRH IN EXCESS OF 250 M2/S2, THOUGH THIS COULD BE LIMITED IF SIGNIFICANT MIXING OCCURS DURING THE DAY RESULTING IN >1000M LCL HEIGHTS. SHOULD THE TORNADO THREAT MATERIALIZE, A STRONG TORNADO CANNOT BE RULED OUT. STORMS WILL HAVE A TENDENCY TO GROW UPSCALE FAIRLY QUICKLY BY EARLY THIS EVENING, POTENTIALLY INTO A WELL-DEVELOPED MCS PROPAGATING ALONG THE COLD FRONT. DAMAGING WINDS WILL BECOME THE PRIMARY THREAT, WITH A FEW GUSTS IN EXCESS OF 75 MPH POSSIBLE, ESPECIALLY WITHIN BOWING SEGMENTS. A MESOSCALE CORRIDOR FOR FAIRLY WIDESPREAD AND POTENTIALLY INTENSE DAMAGING WIND GUSTS COULD EVOLVE IF A BOWING MCS CAN DEVELOP FAR ENOUGH WEST ALLOWING FOR MAXIMIZED PARAMETER SPACE AHEAD OF IT, AND THIS POTENTIAL WILL BE MONITORED TODAY. BY MID TO LATE EVENING, ORGANIZED STORMS WILL BEGIN TO GRADUALLY WEAKEN AS THEY SPREAD EAST AND BECOME FAIRLY DISORGANIZED AS THEY BECOME UNDERCUT BY THE COLD FRONT.