2014-10-10_PERMIT FILE - C1996083A (22)

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1I The shape and orientation of the North Fork Valley is such that the drainage (or katabatic) flow is the dominant flow for most hours of the day. This occurs because the westerly draining orientation of the valley width in its upper reaches, results in much of the upper valley bottom being in shadow during the early and mid - morning hours. The air adjacent to the south sides of the mountains on the north side of the river is warmed and rises directly up the side of the mountains. Since the lower valley is only sparsely vegetated with generally dry soils, the greatest upslope flow occurs in this area. The air from the upper reaches of the valley thus continues to drain down the valley until nearly noon (particularly so in winter when the sun angle is low) and up the valley (or anabatic) flow does not begin until mid -day. Again, because of the narrowness of the upper valley, the heating of the valley floor (say above Somerset and beyond) is terminated by topographic shading by mid- afternoon, and with the air still being warmed and rising in the lower valley, the North Fork may be one of the best examples of mountain - valley flow in the State of Colorado. Because of the narrowness of the upper valley, the cold air layer becomes quite deep with the wind velocity at the mouth of the upper valley usually reaching a maximum in the early morning hours. Prevailing winds are from the south southeast with wind speeds of ten miles per hour occurring in June. Below Paonia the wind speed appears to decrease sharply as the air spreads over the lower valley. Because of this strong drainage wind, frost pockets are not allowed to form, thus creating a favorable microclimate for fruit tree farming. (1)(c) Mean monthly temperature and temperature ranges. The closest weather station to the permit area where temperature data is available is the Paonia weather station. According to the Bowie Resources No. 1 Mine permit, page 58, the Paonia station was established in April 1892, on the east side of town. It was deactivated in September 1898 and reactivated in December 1905 at the PR -14 2.04-71- 03/14