Omega and negative EPV 03/06 UTC.

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The data on this cross-section indicates that the instability was located at a lower level in the atmosphere by 06 UTC. A mid-level maximum of omega is still evident, however it is no longer co-located with instability. However, a low-level maximum of omega over northeastern Pennsylvania is co-located with instability (as indicated by the negative (shaded) EPV). Thunderstorms were occurring over northern Pennsylvania, where the low-level omega was co-located with low-level instability.