U.S. Weather: Cleon Still Going Strong; Dion on Deck


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freezing rain

Freezing rain can bring down power lines and shut down roads; are you ready for Cleon and Dion? Image by Paulabflat

An unusually cold and stormy weather pattern covers the continental United States today. Residents of a wide band from Texas and Okolahoma to New England are still feeling the impacts of storm Cleon; meanwhile, storm Dion is entering the Pacific coast.

A pronounced wiggle in the jet stream is responsible for this rare occurrence of bad weather from coast to coast.

Winter Storm Cleon Begins to Wind Down

The major ice storm has knocked down power lines and trees, and caused school closings – in Texas, Arkansas, Illinois, Indiana, and Kentucky. School children may be cheering, but parents are struggling with power outages and nearly impossible travel.

Daytime heating will narrow the zone of freezing rain in the areas that were affected overnight, but tonight’s cooling will fuel another ice event farther northeast, and freezing rain will most likely occur today in Pennsylvania and New York, and tonight in New England.

Winter Storm Dion Arrives

The effects of Dion will arrive today in the form of unseasonably cold weather throughout the western states, along with precipitation that will fall as snow in some lower elevations that normally get all rain. As the storm moves east, another round of freezing rain could occur Sunday and Monday in the same regions that experienced the wrath of Cleon.

The Jet Stream is Causing This Stormy Weather

A river of air a few miles above the ground controls our weather in the mid-latitudes. This jet stream flows from west to east, but its motion is not smooth in either shape or speed. Waves ripple through the jet stream, with dips (troughs) and crests (ridges). The shorter waves are typically a thousand miles or so from crest to crest, move from west to east, and control our day-to-day weather. The sharper the dip and the faster the wind flow within the wave, the more unsettled the weather. The longer waves tend to be stationary or  move slowly westward. Typically there are five or six long waves that circle the globe.

Stormy Weather: The Current Pattern

Inclement weather is normally associated with troughs. Right now a very long and pronounced trough in the jet stream covers all of the continental United States. This situation is the result of two long-wave troughs, one near each coast, merging to form one abnormally broad area of cold and stormy weather that covers most of the lower 48. As short-wave troughs travel through this longer wave, nasty weather accompanies each one. To this scenario we can add the local conditions that arise when warm, humid air from the Gulf of Mexico meets cold air coming south from Canada. This is the setup for freezing rain.

Dion and Cleon: Will the Pattern Change?

Long-wave troughs tend to be anchored by orographic (higher-elevation) features, especially mountains. A long-wave trough typically persists over the Rockies, for example. Shorter waves coming around this trough cause storms in the southeast, midwest, and eastern seaboard states. There is no indication that the current pattern will change substantially within the next couple of weeks, so most of the United States will experience below normal temperatures. However, the conditions that are producing the damaging ice storms will not be present.

With the passage of Dion, the winds within the long-wave trough will weaken and flatten; by Tuesday, a period of cold but less unsettled weather should begin.

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