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applied to the regi ons wes t of the 3scade Divide. Distance intervals ed in HMR No. 43 are larger than in present study. because of generally .ronger winds wi thin more stahle air n that region. s a result of stimulation L onsiderations. another smooth veloping line was drawn from the adian border to the Mexican border. oughly 20 mi east of the b~~~~_e t u ~1.QP~~ and this line was ntually !.d_~~~ep._.~.Jep;:~s~!l~~.E~__~ l ical di_visiQ!1.Q...~ t~e~f! __qr.9..a:r.~..ph!c _apci '-roiraphic. . !,e~ion!: The adopted ation of' the orographic paration line (05L) is shown in 'figure 3.1. An additional orographic . bdivision was necessary in Montana to lineate the orographic region "closing the Bear Paw Mountains. 'other subdivision of similar nature a drawn around the Black Hills in oth Dakota. It should be noted that in following e rather simple guidelines for ,. ating the orographic separation ne, \,l~cemen..t._.was somewhat ,,~~vious !o.~_, _Mgn.t.ana ,arid .Colorado. In ming. however. placement is not ways as clear. This is especially case in the central part of the ate where no notably steep slopes . cur and the flow is more along the 29 rriers than normal to them. In this gion. the outline of the Wind River l1ey (fig. 3.1) was followed. 2.2 First Upslopes 9 I ,- '-"'1 101 29 Figure 3.1.--Study region showi~ line separating orographic and nonorographic regions (orographj,c separation line - 081). After separating the broadscale ographic/nonorographic regions. the ographic region was examined for ssible further subdivision. One adily apparent subregion was the ~t upslopes. When considering the flow of moist air in passi~ over such terrain, tne!irst up~~es._.ge!l~!'.!lJ.Jy have the greatest effect in produdng ipitation. The secondary upslopes, behind the first upslopes. are effective producing precipitation only to the extent that they rise higher than the rst upslopes, or that the air can descend and be lifted again when encountering e second slopes. 6S .~ \ ~