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I I A gauge site planned to be between the GSC and GTR proved quite difficult to locate. That region consists of a long ridge extending west-northwest from the major hill just south of the TAR. The ridge has steep slopes to either side. With one exception discussed later, the ridge top had very little conifer forest cover. The south facing slope has some aspen forest but mostly low sagebrush while the north facing slope has considerable conifer tree cover. During early September 2003 the lead field technician, very familiar with the area from hunting, surveyed the entire ridge and other potential gauge areas. A few days later one of the authors joined him and walked the ridgeline, examining the few possible clearings the technician had discovered well down the north slope. The north facing slope is very steep all along the ridgeline and has fallen dead trees everywhere, often crisscrossing one another at every conceivable angle. The author and field technician mutually agreed that besides the obvious avalanche danger on such steep slopes, winter travel was impossible by oversnow vehicle and even by snowshoe. The only practical site found anywhere between GSC and GTR was on a saddle atop the ridge where GRD (Gauge Ridge) was later established. The saddle is covered by conifer trees and a small clearing was found. Conifer forest did not extend very far to the southwest (typically upwind) before the terrain rapidly became steep without any trees for protection. This was clearly not an ideal site but in the absence of any other choices it was hoped the location would have enough local wind protection to prove adequate. The site proved to be a poor location, but that was not obvious until observations had been made there and compared with other gauge measurements. The GRD gauge also proved to be by far the most difficult to service, requiring a tedious snowshoe trek over steep terrain. I I I I I It also proved difficult to locate a good gauge clearing sufficiently south of GTR to serve as a control site. A well protected clearing was found at the bottom of a steep slope, which was practical to service by snowmobile from the south and east across open terrain. However, this location, known as GSO for Gauge South, was only 1.3 Ian southeast of GTR and only 1.0 km due south (crosswind) of it on the north-south oriented plateau. Consequently, the possibility existed of "contamination" by seeding. That is, seeding might sometimes increase snowfall at this control site as well as at target gauges. While this was a concern, the frequency of possible contamination was not fully appreciated at the time. Scouting further south revealed only aspen forest for a limited distance and then completely open terrain which extends southward from many kilometers. The GSO gauge was located as far south ofthe GTR as suitable conifer forest exists. However, later examination of previous plume tracking data, discussed in Sec. 4, demonstrated that not only was the location insufficiently crosswind to usually escape seeding effects, but would frequently be under the seeding plume, typically 2 Ian wide. The GSO was therefore treated as a target gauge. I I I I I The location of the gauge to be downwind ofGTR was also limited by available conifer forest. A fairly protected clearing was found just east of Fairview Lakes. This gauge site was named GDN for Gauge Downwind. It wa<; located 2.0 km from GTR along a bearing 01'70 deg true in a limited area of conifers. Subjectively the GDN location did not appear to have as much forest protection as gauges GNO, GTR, GSO and GSC which were all well protected. However, it was the most protected clearing that could be found in the vicinity. With prevailing westerly flows on top the plateau, it was desired to locate the downwind gauge further south so as to be due east ofGTR. Such a location should have more frequently been under the seeding plume. But only aspen trees or open terrain exist south ofGDN. As with the GRD location, the choice was to use a site which might or might not prove suitable or to take no observations. It should be realized that selection of forest clearings for snowfall measurements is partially an art as well as science. Only local wind observations during snowstorms and comparisons with nearby well-protected gauges will ultimately demonstrate the suitability of a particular location for snowfall measurement. With the definite exception of the ridge top gauge, GRD, and some concerns about adequate protection for GDN, the other four gauge clearings are believed to have performed well in providing accurate snowfall observations. I I I I I 19 I II