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• "Temperatures at Grand Junction have ranged from 105° to -23°, but readings of 100° or <br />higher are infrequent, and about one-third of the wihters have no readings below zero. <br />Summer days with maximum temperatures in the middle and low 90's and minima in the low <br />60's are common. Relative humidity is very low during the summer, with values close to such <br />other dry localities as the southern parts of New Mexico and Arizona. Spells of cold winter <br />weather are sometimes prolonged due to cold air becoming trapped in the valley. W finds are <br />usually very light during the coldest weather. Changes in winter are generally gradual, and <br />abrupt changes are much less frequent than in eastern Colorado. "Cold waves" are rare. <br />Sunny days predominate in all seasons. <br />"Flying weather conditions are generally favorable for operation of light airplanes, with <br />visibilities of 20 miles or more and ceiling of 5,000 feet or higher prevailing approximately 95 <br />percent of the time. Gusty surface winds are rather frequent in the spring and early summer. <br />The prevailing wind is from the east-southeast due to the "valley breeze" effects, but the <br />strongest winds are <br />usually from the south and southwest, and are associated with thunderstorms or with pre- <br />• 'frontal weather." <br />Wind Speed and Wind Direction <br />Wind speed and wind direction are not recorded at the Nucla Mine site nor is it available from the <br />Uravan or Norwood Stations. The closest National Weather Service Station that records wind <br />information is at Grand Junction, Colorado. <br />The prevailing wind direction at Grand Junction is from the east-southeast at a mean wind speed <br />of 8.1 miles per hour. It must be stressed that the information from Grand Junction does not likely <br />apply to the Nucla Mine site. The Grand Junction Station is situated in a valley (elevation 4,849 <br />feet), surrounded by mountains and is greatly influenced by the valley winds rather than the <br />synoptic winds. The mine site is, however, located above a valley on a mesa (elevation <br />approximately 5,700 feet) and is therefore more likely to be subject to the synoptic winds from the <br />west to southwest (Dosken, 1980 and Benson, 1979). <br />• <br />(REVISED MARCH 2006) 2.04.8-5 <br />