Laserfiche WebLink
<br />20 <br /> <br />Rockies had been present for several days or more. A fresh outbreak of <br /> <br />Arctic air was moving southeast across the Great Plains, and it reached <br /> <br /> <br />into northern Texas 24 hours after this time. None of this cold air <br /> <br /> <br />reached west of the eastern front range of the Rockies into Utah. <br /> <br /> <br />Cyclogenesis ahead of the upper trough began as lee troughing in eastern <br /> <br />Colorado 24 hours previously. At the time of these maps, the surface <br /> <br />cylone was split between the older low in southern Nevada and the <br /> <br />developing one in eastern Colorado. Notice that the upper level flow was <br /> <br />nearly parallel with the surface cold front in Utah. Consequently, after <br /> <br />this time the Utah cold front moved only a little further south and <br /> <br />began to weaken as the upper level support was transfered east of the <br /> <br />mountains. <br /> <br />The surface cold front passed the project site at about the time of <br /> <br />these maps and was accompanied by heavy snowfall for several hours. <br /> <br />Figure 7 shows an atmospheric cross section of equivalent potential <br /> <br />temperature that was constructed from the rawinsonde observations taken <br /> <br />at the Adamsville site. The location of the cold frontal surface was <br /> <br />determined from the wind shift boundary. The significant feature <br /> <br /> <br />related to the precipitation for this STORM is the layer of convectively <br /> <br />neutral or unstable air. It begins in the lowest 100 mb 22 hours before <br /> <br />frontal passage and becomes elevated and extends to about 6 hours after <br /> <br />frontal passage. This neutral/unstable layer at low levels has been <br /> <br />identified as a characteristic of the early stages in orographic storms <br /> <br />in Colorado's San Juan mountains (Cooper and Saunders, 1980). However, <br /> <br />the lowest level blocked flow that was found there is not present here. <br /> <br />The greatest convective instability occurred from eight hours before to <br /> <br />one hour after frontal passage. Notice that there was a shallow (ca. SO <br /> <br />~ <br /> <br />~ <br /> <br />~ <br />