COLORADO – Here’s my next item in a series of articles giving viewers insight into those quirky terms we use during our forecasts. When you hear them for the first time you may wonder if the idea is new. If the term was recently ‘invented’, or even if it is a real thing!
Today’s topic – Cold Air Damming
This is a phrase that relates cold air at the surface, and mountainous terrain nearby. Cold air, because it is heavier than warm air, sinks low.
Picture our topography here in Colorado. Tall mountain chain, Plains east. Winds usually come over these mountains, from west to east. Imagine a pool of cold air in the Plains, banked up against the mountains. Even if there is a moderate west wind coming over top of the peaks, it may take hours and miles downstream, for that west wind to flush out the cold air, 5000 feet below in the Plains. And, if the surface wind in the Plains is East, that low level surface wind will fight the higher aloft west wind from breaking up that cold air.
So, cold air damming refers to the cold surface east wind pushing that cold air against the (right) side of the mountain range, and stubbornly holding on, while warmer west winds are flying over top of us along the I-25 corridor.
Needless to say, this can wreak havoc on our forecasts, because all one has to do, to blow a forecast, is miss the low level surface wind in the Plains. That not only affects the temps, but the sky-cover and the precipitation TYPE!
This scenario is always in the back of our minds, when either an upslope flow develops in the Plains, or a Backdoor cold front passes through.