Spring could bring floods to Phila. region

With the ground as soaked as it has been in at least 75 years, a flood season that is off to a roaring start in the Midwest could also turn dangerous in the Philadelphia region and throughout the Northeast, government meteorologists warned yesterday.

"We're primed for a rough spring," said Douglas LeComte, a forecaster with the Climate Prediction Center.

Soil-moisture levels from Maine to Oklahoma - a 1,000-mile arc that passes through Pennsylvania - are at "unprecedented" levels in the period of record, dating to the early 1930s, LeComte said.

At a morning briefing, he blamed what he called "a jet stream on steroids" for overfilling rivers and streams and piling on the snowpack in the Northeast and the Midwest, where recent heavy rains have been blamed for at least a dozen deaths. The west-to-east jet stream winds, which form at the boundaries of warm and cold air, help generate and move storms.

Major flooding has hit more than 250 towns in 12 states, according to the National Oceanic and Atmospheric Administration. And the season is just beginning.

"All the ingredients" are there for more flooding in a broad area that covers virtually the entire Corn Belt, the Mississippi and Ohio Valleys, all of Pennsylvania, New Jersey and the entire Northeast except extreme northern New York, Joanna Dionne, a National Weather Service meteorologist, said during the briefing.

In the last two months, rainfall has been significantly above normal in every Pennsylvania, New Jersey and New York county, according to the National Weather Service. But the local flood outlook would have been even bleaker if the snowpack had been deeper in the Delaware, Schuylkill and Lehigh River headwater areas and in the immediate Philadelphia region.

So far, Philadelphia has had a mere 6.2 inches of snow officially.

Meteorologists attribute the winter's peculiar behavior to one of the strongest La Niña events on record. During a La Niña, surface waters of the equatorial Pacific become cooler than normal over an enormous area.

That disturbs the atmospheric circulation in such a way that storms and cold air pass to the north and west of Philadelphia in winter. This year, interior New England and points north, as well as parts of the Midwest, were hammered by snowstorms that did little more than wring out nuisance rains over Philadelphia.

Some of the storms were especially potent because of a hyperactive jet stream energized by a disturbance in the far western Pacific, LeComte said.

La Niña is finally weakening, said Mike Halpert, a meteorologist at the Climate Prediction Center, and it appears that winter may try to make up for lost time in the mid-Atlantic region. Some snow is possible early tomorrow, and the outlook for next week is chilly.

"We have a reluctant spring," said Joe Bastardi, the long-range forecaster at AccuWeather Inc.

"People want to be able to tiptoe through the tulips on April 1. I highly doubt they will have that opportunity."