| OCR Text |
Show beginning or the end. ( See Fig. I) Prolonged overcast ( south influence) at the end of storm period is often accompanied by rising temperature, as long as overcast persists, and at times light rain. Clearing skies, ( particularly if clearing occurs at night) often mean a sharp, short drop in temperature. The advent of such sudden clearing is at times marked by short, violent thunder storms, representing the clash of north and south influence. Although temperatures drop when the skies clear, if the north influence persists, a sharp rise can follow in k8 tfours. Usually, it is this post- frontal activity, of the storm system that is responsible for troublesome rain crust or tapioca at the top of the pack, which forms an undesirable old snow surface for future layers. SNOW TYPES ( See Figure II) The most important single feature in the pattern of deposited new snow: types is the presence of graupel, or pellet snow, in almost all new snow layers. Snow densities are high and parallel with the high prevailing storm temperatures. Overnight low temperatures may drop to 10- 20 degrees. However, daytime temperatures, even during storms in mid- winter, are often above the freezing point. It is not uncommon to have mixed rain and snow in mid- winter. The result is stratification of graupel, rain crust, slush, snow types of lighter density, or even what might be considered powder, due to difference in day and night temperatures. The graupel will vary in size from a pin point to £ in. diameter- Such a layer persists in |
