Friday, June 4, 2010

SE Iowa or NW Illinois tomorrow...

The NAM looks less than ideal, with the GFS slightly more kind. I'm not inclined to believe one over the other. I'm not expecting a big day, but a surprise tornado is certainly possible in an area from Ottumwa, Iowa to Galesburg, Illinois. Current thinking is that the outflow boundary from the dying mcs currently located over western Iowa should lay across the Highway 34 corridor in southern Iowa. Seasonable moisture with td's approaching 70 or even slightly above in some areas along the boundary coupled with ample surface heating and the approaching shortwave arriving in eastern Iowa in the early evening should aid in the development of isolated severe thunderstorms by early evening in southeast Iowa. Surface convergence should also increase considerably in the region as the boundary sags southward. Low level shear won't be overly strong, but with the aid of the potential interaction along the outflow boundary I think storm rotation should be manageable. HP storm mode is a concern.

Current thinking is that a tornado or two is possible in southeast Iowa tomorrow evening in an area around Ottumwa to Mount Pleasant, Iowa. This area could shift tomorrow with the movement of surface features, but se Iowa into far nw Illinois has seemed pretty consistent over the last day or so.

Saturday looks potentially big in central Illinois.

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