Cold, rain-chilled air is forcing outflow boundary to move southward, turning winds to the north & northwest at Lafayette, Attica & Covington. Meanwhile, warm front is trying to move northward in response to disturbance riding through central Illinois.
The cold outflow boundary is tend to shove warm front to the south & the two are merging over Fountain, Montgomery & Tippecanoe to Clinton counties, separating 50 from nearly 70 degrees.
This is resulting in enhanced surface to 1 km low-level shear in this zone of up to 35 knots.
Helicity or spin values of up to 300-350 m2/s2 are also found in this zone.
This overlaps a little tongue of +500 J/kg of surface CAPE or surface buoyancy.
This is resulting in a little nudge of 10% conditional tornado probability getting into this zone.
So now to 1-2 a.m., an isolated severe storm or two cannot be ruled out with any storm(s) that can really organize.
A randomhailer of pea to quarter size is possible anywhere (north, along or south of the warm front/gust front or outflow boundary) & risk of an isolated brief, weak tornado just south of the warm front. The risk of an isolated severe gust will exist just south & south of the warm front.
It is possible that this risk moves a bit northward as the warm front tries to drift northward. However, any isolated severe risk will diminish before 2 a.m.
So, rain/storms begin to migrate northward & then weaken with time.
Isolated showers Wednesday morning will give way to clouds/sun & windy, humid conditions & highs 73-80.
Some scattered storms will pop late afternoon-evening.
Isolated severe storms are possible.
Another round of showers & storms is likely Thursday morning. An isolated severe storm is possible, followed by clouds/sun & 70-78 Thursday after overnight lows in the 60s.
A final wave of showers & storms may pass Thursday evening-night.
An isolated severe storm cannot be ruled out if it gets unstable enough.
River flooding will increase over the weekend & next week & ponding of fields & in lawns & on roads will occur with these downpours.
Friday looks dry with sun & 62-67.
Some rainfall is possible Saturday with 62-66.
Warm front will meander back & forth of the area next week, resulting in off & on showers & storms & some severe risk. Temperatures will also vary greatly over the area at times between 50s & 60s & 70s & 80s.
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- April 4, 11 PM Weather Forecast Update