Last evening, after two days of clear, cold weather, a shelf of high clouds stretched across the western horizon, lit by the colorful rays of the setting sun. Along the leading edge of this sheet of ice crystals was a series of ripples, giving the appearance of pink beach sand, molded by incoming waves.
This spectacle was produced by low pressure over the Great Plains, injecting moisture into the upper layers of the atmosphere and creating turbulence as the rising, warmer air encountered the frigid air at an altitude of 40,000 feet. Later in the evening, this thin veil of cirrus clouds moved across central Missouri and produced a halo around the bright crescent moon.
Such high cloud formations usually signal an advancing front and, in this case, a deep trough is forming across the western U.S.; this dip in the jet stream will bring heavy snow and frigid temperatures across the Rocky Mountain corridor and spawn Santa Ana winds in Southern California. Ahead of the front, milder air is pushing up from the Gulf Coast and we'll enjoy a brief respite before winter reclaims the Heartland.
