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If future. re-analysis of the research programs indicate that revised criteria are appropriate, NAWCts seeding criteria. can be altered to take such criteria into consideration. 2.2 Rawinsonde Data Sources In recent years (since 1977) rawinsonde data have been collected from sites near Milford, Beaver J and Blanding (see Figure 2-2, open circles). NWS operated rawinsonde data sites outside of the target area are shown in Figure ,2.2 as solid circles. Generally the five NWS sites nearest the target, namely, Salt Lake City, Grand Junction, Winslow, Desert Bange, and Ely are ,more representative of target conditions than are those further away but even the five closest to the target are some distance away from most of the high yield target areas. In adqition to the problems created due to this spatial resolution question, even greater problems in interpretation exist because of the temporal resolution . The NWS .rawinsonde si tes routinely sample the upper atmosphere twice daily at 12 hour intervals. Since release times are not tied to sampling any specific portion of a passing storm they randomly sample various portions of a storm and can frequently entirely miss whole segments such as a frontal zone. Experience has shown that within a storm period, conditions can change rapidly and certain parameters affecting seedability criteria can be easily misinterpreted when the sampling in.t.erval is as long as 12 hours. This can be illustrated in Figure 2.3 which shows a time section plot of cloud top temperature and height, cloud base temperature and height, and cloud base mixing ratio from serial soundings taken at Richfield this past winter during a storm period. At OlOOZ on March 3, 1980 (time 0) the sounding indicated a cloud top at 5971 m, temperature 2-7 ,.;.j~......:::..:~..:;