The Bridger Range, Montana, 1986-1987 snow pack augementation program

A winter orographic snow pack augmentation program was conducted for the benefit of a ski resort near Bozeman, Montana, during the winter of 1986-87. The operational goals were to help ensure a timely opening of the resort and to increase the snow pack, especially for the Christmas-New Year's holiday season. Seeding was from a single surface-based AgI generator located well up the west slope of the Main Bridger Ridge. Three hundred and eighty five hours were seeded during the period of 11 Nov. to the end of Feb. A research program was ``piggy-backed'' upon the operations to test the targeting effectiveness, to document the existence of supercooled liquid water, to examine the microphysical aspects of the seeding and to determine if the seeding increased the seasonal snow pack. Supercooled liquid water was documented and AgI was verified as crossing the Main Ridge by an acoustical ice nucleus detector. Analysis of sedimentation plate images suggested that aggregation and riming were important contributors to the rapid growth of crystals falling on the ski resort, the center of which was 4 km SE of the generator. Target-control analysis of snow course data suggested 35 to 50% additional seasonal snow pack within the target.