Monday, August 20, 2007

Severe Weather Possible this Afternoon

A remnant surface trough / dryline will interact with a nearly stationary surface boundary located over extreme eastern Nebraska and western Iowa. 40-50kts of deep layer shear exists which is ample for supercells along with isolated tornadoes possible given the low level directional shear in place.

EHI values, which is measured by the amount of CAPE and storm relative helicity (in this case the lowest 1km), are above 5 for eastern Nebraska. In general, 0-1km EHI's above 2 can support a decent tornado threat.

A weather watch, possibly a tornado watch, may be needed later this afternoon for the affected areas.

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