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that basically all the seeding signal was contained within the 69 EUs where targeting was highly likely. The same partition ~xc!uded northwest flow ETJs expected to transport seeding plumes south of the target gauges. . A dual partition used the same wind direction partition combined with exclusion of the larger 20% of natural SWE amounts observed at control gauge GNO. Overall results were encouraging, suggesting that real seeding effects were particularly detectable and pronounced when natural snowfalls were no more than moderate in spite of reduced correlations with the control gauge. . Results were analyzed for several other single and dual partitions, the latter always including the southwest quadrant winds at the seeding site. These results were mixed, ranging from strongly suggestive to somewhat suggestive to inconclusive depending upon the particular partition, gauge and statistical test. A number of partitions provided interesting suggestions but none of the results were as convincing as the wind direction partition or entire population testing. . There were suggestions that seeding may have been more effective when SL W cloud (icing) was detected, when seeding plume temperatures were warmer and when wind speeds were lighter. But rigorous testing of these interesting but mostly inconclusive suggestions would require a larger sample size than available from the limited 3.5 month experimental period. Recommendations for Further Development of Propane Seeding The statistical results from the 2003/04 Utah randomized experiment, together with supporting physical observations during that period and from considerable past investigation at the same location, present a strong case for propane seeding effectiveness in increasing mountain snowfall. To date, applied research into propane seeding has been limited by available resources as federal funding for weather modification research has significantly declined over the past several years. Those who would be critical of limited progress should bear that reality in mind. The randomized propane seeding experiment was not designed to answer all remaining questions, and a number remain. In particular, the downwind extent of seeding effects received little attention. But there is certainly sufficient evidence to justify further development of this promising emerging technology, especially given propane's (," .. ability to seed significantly warmer SL W cloud than possible with AgI. That fact alone is a powerful argument for continued development of propane seeding for winter orographic clouds in the western United States and elsewhere. It is strongly recommended that a follow-on confirmatory randomized experiment be conducted on the Wasatch Plateau or similar mountain barrier over at least three winters. The experiment would require a minimum of three high elevation propane seeding sites separated by 2-3 kIn crosswind distance. A significantly larger precipitation gauge network would be required extending further downwind. The central downwind gauges should be targeted by at least one ofthe seeding sites as wind directions shifted within a reasonable range. Crosswind control gauges would be maintained both south and north (crosswind) of the target gauges. Because of the difficulties of finding naturally protected clearings in evergreen forest at higher elevations some gauges might require elaborate double-fence wind shields. A numerical model should be verified and used which has the capability of handling local transport and dispersion over the rugged terrain, and with sophisticated microphysics. The experiment should be provided with comprehensive physical observations to include a microwave radiometer to monitor the SL W cloud zone, and to provide much improved microphysical measurements, both in target and crosswind control locations. These specific recommendations for a propane seeding experiment follow the general recommendations of the most recent (1998) American Meteorological Society Policy Statement on Weather Modification which stated, "Whereas a statistical evaluation is required to establish that a significant change resulted from a given seeding activity, it must be accompanied by a physical evaluation to confirm that the statistically observed change was due to the seeding." Until that approach is followed, with results published in the peer reviewed scientific literature, there will continue to be controversy and uncertainty concerning winter orographic cloud seeding effectiveness with either AgI or propane. With ever developing demands on limited water resources in the western states, and recent evidence of declining mountain snowpacks since about 1950, policy makers should be able to make decisions based on physical reality as revealed through sound scientific inquiry. Such information remains limited in the field of winter orographic cloud seeding. In the meantime, water users interested in using cloud seeding to increase the winter mountain snowpack will continue to make 12