Tuesday, October 2, 2018

A Forty Degree Swing

Autumn is the season when those of us along the Colorado Front Range often experience a 40 degree (F) temperature swing in the course of a day, awakening to a temperature in the upper thirties and basking in warmth near 80 degrees by mid afternoon.  Such broad temperature ranges are common in arid and semiarid regions across the globe, especially those that lie at relatively high elevation in the Temperate Zone.

By October, the longer nights, high elevation and dry air augment heat radiation, permitting overnight temperatures to fall near freezing.  During the day, intense sunshine, dry (dense) air and, on some days, a downsloping wind push afternoon highs into the seventies or eighties.

Of course, potent cold fronts or a persistent upslope flow may disrupt this cycle, as is forecast to develop later this week.  By early next week, daytime highs may be within 10 degrees of the overnight low and the first snow showers of the season are expected to dust the urban corridor.