CLIMATE 



The climate of the two watersheds com- 

 prising the study area is generally representa- 

 tive of large areas of midelevation 

 (7,000-8,000 ft.) mountain country in the 

 Intermountain region. Winter weather pat- 

 terns are primarily influenced by frontal 

 systems moving in from the Pacific North- 

 west. For 6 months of the year (November- 

 April), winter prevails, and average monthly 

 temperatures are uniformly below 30 degrees; 

 however, periods of subzero temperatures are 

 both infrequent and of short duration. Heavy 

 snowfall accounts for about 80 percent of the 

 yearly precipitation. Summers are short, cool, 

 and dry. Most summer storms are convective 

 thunderstorms, although a few are associated 

 with weak fronts moving eastward from the 

 Pacific. Prevailing winds are from the south 

 and southwest carrying summer moisture 

 aloft from the Gulf of Mexico. 



As in most of the Intermountain region, 

 aspect greatly influences the study area's 

 climate by affecting radiation, temperature, 

 wind, and moisture regimes. Response to 

 these influences is markedly reflected in the 

 local vegetation patterns. 



A climatic station was established on the 

 West Branch watershed (fig. 2) in May 1971. 

 Total and net radiation, air temperature, rela- 

 tive humidity, wind direction, and windspeed 

 at two elevations are being continuously re- 

 corded. 



Precipitation 



The precipitation network on the two 

 study watersheds consists of one recording in- 

 tensity gage, three storage gages, and two addi- 

 tional intensity gages used only during the 

 summer months. Storage gages have been in 

 use since 1956, except for the years 



1960-1962. Summer intensity records are 

 available for 1962 and from 1964 and 

 thereafter. The network is supplemented by 

 long-term (up to 30 years) summer intensity 

 records from 14 nearby stations at elevations 

 ranging from 4,350 to 9,000 feet on the 

 DCEW and from two additional storage gages 

 at 6,800 and 7,500 feet elevation in the Farm- 

 ington Creek drainage where the study water- 

 sheds are located. 



Average yearly precipitation on the study 

 watersheds is 45 inches, and, as noted earlier, 

 80 percent of this occurs as snow. The month- 

 ly distribution of precipitation is presented in 

 figure 3. The June-through-September period 

 is the driest of the year, and a 9-year average 

 for this period was only 5.06 inches. How- 

 ever, summer rainfall is quite variable, ranging 

 from 1.01 to 12.82 inches per year. Converse- 



6r 



■ ■ ■ I I I I ■ ' I I 



ONDJFMAMJ JAS 

 MONTHS 



Figure 3. — Distribution of average monthly 

 precipitation, 1956-1959. 



4 



