On Reading the Clouds

Fairbanksans and Tanana Valley residents can use their powers of observation to deduce, with a fair degree of reliability, the probability of snowfall when it is cloudy. Just look to the south.

If there is a bright band between the clouds and the Alaska Range, it probably will not snow. If the Alaska Range is obscured by clouds (ice fog doesn't count), or if you can only see the base of the mountains, the chances for snow are good.

Air flowing into the Interior from the south is forced to rise over the mountains. As it does, it drops much of its moisture. Descending into the Tanana Valley, it causes temperatures to rise and some of the clouds evaporate, producing the bright band. Continuing to the north, the air rises again and the clouds thicken, but because the air beneath is warm and dry, little precipitation reaches the ground.

However, clouds moving in rapidly from the west are likely to portend snow. Air moving in from the west encounters no mountain ranges, so it retains its moisture, which is released as snow when it rises over the colder air of the Tanana Valley.

Clouds moving in from the east, like those from the south, generally produce little snow. Neither do clouds from the north, an area which provides scant sources of moisture.