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Cross-section of omega and negative EPV* (shaded) (February 13, 18 UTC 0-24 hr NAM forecast)
Notes:
Focused lift associated with frontogenesis was doubtlessly one factor that produced the intense banding of heavy snow observed over northeast Pennsylvania and the western Catskill mountains during the afternoon on the 14th. Another factor was the reduced mid-tropospheric stability that developed in that area, and became co-located with the focused lift associated with the frontogenesis. The presence of the reduced stability (indicated on these plots by negative EPV*, shaded in blue), juxtaposed with frontal-scale forcing for lift, resulted in a narrowing and intensification of the lift. The plots on this loop shows how the maxima of upward vertical motion became increasing well co-located with negative EPV* as the event progressed.
