During a typical spring, the jet stream undulates across North America, bringing a series of troughs and ridges to any given region; the former allow cool air to spill southward while the latter permit warmth to build northward. Cold and warm fronts separate these air masses, bringing intermittent storms and showers through the course of a week.
However, over the past week, a persistent ridge of high pressure, known as a "blocking high," developed over the Pacific Northwest. Shunting Pacific fronts to the north, this ridge also brought a steady, southerly flow into Alaska, producing temperatures well above the seasonal norm. At the same time, this blocking high allowed a broad trough to settle over much of the country, with its southern boundary stretching from Texas to the Mid Atlantic region. Upper air disturbances, moving eastward along this "stationary front," directed a series of storms across the same swath of country; such "training" results in heavy precipitation totals and eventual flooding.
Now that the Pacific high is breaking down, storm fronts will resume their typical march across the continent and this week's stationary front will be swept off the map. As a result, both Alaska and the Southeast should return to more seasonable weather patterns.
