Wednesday late afternoon update.....
The SPC has kept the 30% outlook for tomorrow the same from this morning's update.
This is an enhanced slight risk area including....
The 15% or slight risk area has been expanded northward all the way into Michigan and much of Ohio. This includes.....
There are 2 chances for storms. During the day, some storms could become severe in the afternoon. In the evening, another line comes through with a severe risk again. Evening timing is uncertain as this could be late evening.
The SPC says.....
For the afternoon: THE STRONGLY SHEARED BUT WEAKLY UNSTABLE ENVIRONMENT COULD BE SUPPORTIVE FOR ORGANIZED TSTMS WITH ANY SEMI-DISCRETE STRUCTURES THAT CAN EVOLVE WITHIN THE WARM SECTOR...WITH AN ATTENDANT THREAT FOR DMGG WINDS AND TORNADOES /PERHAPS ONE OR TWO STRONG/ POSSIBLE. HOWEVER...THE STORM MODE IS LIKELY TO BE SOMEWHAT COMPLEX/MESSY INITIALLY PRECEDING AN UPSTREAM COLD FRONT.
For the evening: WHILE THE DETAILS ARE STILL SOMEWHAT UNCLEAR...A CONTINUOUS LOW-TOPPED CONVECTIVE LINE APPEARS LIKELY TO DEVELOP AND RAPIDLY SHIFT EWD ATTENDANT TO A RAPIDLY DEEPENING SFC LOW. WHILE THE PRIMARY THREAT WILL LIKELY BE DMGG WINDS...BOWING/LEWP STRUCTURES COULD SUPPORT TORNADOES EMBEDDED WITHIN THE LINE...GIVEN THE DEGREE OF LOW-LEVEL SRH PRESENT
NWS Louisville: As for SVR potential, storm-relative helicity will be off the charts, but the limiting factor will be instability. NAM12 forecast soundings for 03Z Friday support a very narrow ribbon of instability just ahead of the cold front, which is a fairly typical mode for severe T-storms in the Ohio Valley. Expect something along the lines of a leading stratiform QLCS, with a fast-moving main line right along the cold front. Wind would be the main threat, but it`s difficult to rule out a quick spin-up with so much shear. Worst weather looks to be late in the evening as the front moves through. Even ahead of the main line, it will not be a pleasant evening to be outdoors, with a wind-driven rain and gusts near 40 mph.
NWS Paducah: Strong deep layer shear and at least modest instability will support the potential of strong to potentially severe convection. Despite marginal instability the wind field will promote bowing segments and the risk for damaging winds. Strong low level shear profiles will also favor the potential of isolated tornadoes.
NWS Indianapolis: SHEAR WILL BE INCREDIBLY STRONG THROUGH MUCH OF THE DAY AND INTO THE EVENING. HOWEVER...INSTABILITY WILL BE DIFFICULT TO COME BY WITH AMPLE CLOUD COVER AND SHOWERS ACROSS THE AREA. GIVEN THE INCREDIBLY STRONG DYNAMICS OF THE SYSTEM HOWEVER...THIS MAY NOT MAKE MUCH OF A DIFFERENCE. ANY SHOWER OR STORM WILL BE CAPABLE OF MIXING DOWN SOME OF THESE SIGNIFICANT WINDS...AND THE SLIGHT RISK IS DEFINITELY REASONABLE EVEN IN THE LIKELY SPARSE THUNDER TO BE FOUND.
NWS Nashville, TN: THE LOW LEVEL SHEAR AND HELICITY ARE EYE OPENING ENOUGH TO WARRANT THE MENTION OF TORNADOES TOMORROW.
Tomorrow morning the SPC will break down the severe types into percentages....tornadoes, wind damage and large hail. The models have increased the instability a bit. It is still not high, but any increase along with the shear values will certainly increase the severe potential.
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