Snowfall in the Sierra Nevada. 



313 



the mean date at which all snow is of¥ the ground at 

 Summit is May 26th. The mean date at which it is 20 

 inches deep is May loth, etc. In this way we complete 

 our curve along A B E F G, and throwing out small 

 irregularities, may call the smooth curve I H G, the mean 

 curve of melting at Summit Station. It will be borne in 

 mind that this curve includes the light snowstorms of 

 April and May. We may now compare our mean curve 

 of melting with actual curve of any given year. If the 

 actual curve falls below the mean for the most part, the 

 season is a dry one, — that is to say, the rivers will be 

 low and traveling easy in July. If, on the contrary, the 

 actual curve of melting falls far above the mean, the 

 snow will lie long in the mountains and the floods will 

 come late. It is not necessary to have the entire curve 

 of melting in order to make a very fair prediction of the 

 state of the coming summer with respect to the mean of 

 the past ten years. By the first of May enough of the 

 curve of melting can be platted to show the general trend, 

 and any late storms give rise to very light snow, which 

 goes off rapidly. For example, it may be said of the 

 summer of 1908 that it will be slightly below the average 

 in snow, even though the snow on the ground at Summit 

 now* is above the normal. 



It remains to be seen what constitutes a normal snow 

 depth in summer. It will be seen that the summer of 

 1902 follows almost exactly the mean curve of melting. 

 So also does the summer of 1903. Those who visited 

 the King's and Kern river canons during those years 

 will have a general idea of the amount of snow found 

 there in July. Granite Basin on the Middle-South Fork 

 divide was free of snow on July 15th. The basin at 

 the head of Kern River was free of snow July ist. The 

 Troga Road between Yosemite and Lake Tenaya was 

 free of snow before July ist. 



The record of snow on the ground at Summit Station 

 can be found each day in the Weather Bureau's Report 



* June I, 1908. 



