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might be expc:cted that a real seeding signal would be more evident during light to moderate natural sno.....falls than during hea\)' snowfalls, these results are n:markable In view of considerably weaker associations (correlations) with the control gauge. Table J. HAS dlrL'Clion panltion <"" 270 deg eombincd .....ilh GNQ SV.'E<= 0.05 inch: 24 pair;. 30 seeded and 25 nonscedcd Pooled R,- Target- randomiLL-d l-taik-d<)5% G!\:O Samp!.: I-tailed Confidence Gauge Correlation ~IDR P-\'alue [nlenal GSC 0.52 1.30 0.10 1.16-x: GTR 0.67 1.32 0.04 UN-x: GSO 0.58 1045 0.01 I.2I-x GON 0,60 1.51 0.02 1.20-x Somewhat encouraging suggestions resulted from other single and dual partitions mentioned above but not presented in detail here. There were suggestions that ell"ective seeding might have been associated with the presenceofSLW as detected by icing sensors. with wamler than median liAS temperatures and .....ith less than median liAS wind spc:eds. But none of these tested partitions provided results as convincing as those already noted. It is suspected that tack of a significant seeding signal for SL W (icing) partitions was partial due to limitations in the icing rate sensors discussed in the references. -'lost of the resulting statistical suggestions should be regard.;-d more as tantalizing than as conclusive. The main underlying problem IS very likely the limited population sizes tested when any two partitions .....ere app1i.;-d. If any actual s.xding effects existed. the available sample size was too limited to det.;-ct them to an acceptable level of statistical significance. Such results should be consid.;-red inconclusive, neither demonstrating an actual seeding etT.;-ct /lor the lack of olle. Only testing a larger population than av'ailable would alTer the possibility of providing more definitive results. The most solid and imp(lnam results of the statistical testing can be: summarized as follows. It is highly likely that a real seeding e1Tect resultoo. from propane seeding when transport wmds carried the seeding plume mer the target gauges. Overall. seeded units provided at least 20'% more snowfall than nons.xded units. Based on those results. it was hypothetically estimated that if all hours containing the 69 EUs had bl,.'t'n operationally seeded. the overall precipnation increase would have been 80io in the Mseasonal" precipitation averaged for gauges GSC and GTR for the 3.5 month expc:rimental period. This result was provided both by considering the mean residuals from the pairs testing and from the mean double ratio testing .;-mphasized above. Case Stud~' Anal~'sis A case study analysis was perfomled for three adjoining EUs on 21 December 2003. with two of the EUs nonseeded and th.;- middle EU seeded. By chanc.;-. this particular seeded EU coincided .....ith a time period having minimal natural snowfall. seldom obser\'Cd during other EUs. The adjoining nonseeded EUs had considerably more natural snowlall than the s.;-.;-ded EU. both with highest accumulations at the control gauge. But that gauge received only 0.009 inch during th.;- seeded period while targ.;-t gauges had 2 to"; times as much SWE. increasing with distance downwind ofth.;- seeding site. The most convincing evidence that sc.;-ding produced much of the increase was provid.;-d by examination of 2D-C probe ice panicle images from TAR. Th.;-s.;- were very similar to those published lTom pulsed seeding experiments conducted during earlier winters. As seen in Figure 5. bas.;-d on the :m-c probe observations of individual ice crystals. the see-ded images .....ere relatively small and generally unifonn in size and shape. They were in much higher concentrations than observed during the adjoining nonseeded pc:riods which had much greater natural snowfall rates. The first nonseeded period would be c1assilied as having heavy snowfall rates and the last as having moderate rates. Even with conservative assumptions Iktailed in the references. it was estimated that seeded snowfall rates exceeded 0.010 inch per hour at the core target gauges and likely approached twice that rate at the do.....nwind gauge. Such seeding- produced precipitation rates are in good agreement with earlier cas.;-s study e'l;pc:rim.;-nts in Utah and elsewhere in the Intermountain West. .