The reason for the sudden change in the nature of the convection goes back to a very strong storm that was occurring about 35 miles (~60 km) to the east, near Greeley, Colorado.   At about 8:30 p.m., this storm put out a very strong, low-level outflow.

      A narrow (but intense) low-level jet developed along the northern edge of this outflow, and reached Spring Creek (near co-ordinate 0, 0 on the above figure) just before 9:00 p.m.   The upslope associated with this accelerated flow was much more significant than that which had occurred during the earlier part of the evening.   This figure shows the 0.5 degree tilt, dual-Doppler wind vectors computed using the CSU-CHILL Doppler and the WSR-88D at Cheyenne, Wyoming.   Click here to view a   radar loop   for the period 0216 - 0400 UTC.

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