NOAA: Imminent Flood Threat in Midwest, South and East Also at Risk

March 16, 2010

Major flooding has begun and is forecast to continue through spring in parts of the Midwest according to NOAA’s National Weather Service. The South and East are also more susceptible to flooding as an El Niño influenced winter left the area soggier than usual.

Spring 2010 Flood Risk Map

Spring 2010 Flood Risk map.

High resolution (Credit: NOAA)

Overall, more than a third of the contiguous United States has an above average flood risk –– with the highest threat in the Dakotas, Minnesota and Iowa, including along the Red River Valley where crests could approach the record levels set just last year.

Supporting the forecast of imminent Midwest flooding is a snowpack more extensive than in 2009 and containing in excess of 10 inches of liquid water in some locations. Until early March, consistently cold temperatures limited snow melt and runoff. These conditions exist on top of: above normal streamflows; December precipitation that was up to four times above average; and the ground which is frozen to a depth as much as three feet below the surface.

“It’s a terrible case of déjà vu, but this time the flooding will likely be more widespread. As the spring thaw melts the snowpack, saturated and frozen ground in the Midwest will exacerbate the flooding of the flat terrain and feed rising rivers and streams,” said Jane Lubchenco, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator. “We will continue to refine forecasts to account for additional precipitation and rising temperatures, which affect the rate and severity of flooding.”

“In the South and East, where an El Niño-driven winter was very wet and white, spring flooding is more of a possibility than a certainty and will largely be dependent upon the severity and duration of additional precipitation and how fast existing snow cover melts,” said Jack Hayes, Ph.D., director of the National Weather Service. “Though El Niño is forecast to continue at least through spring, its influence on day-to-day weather should lessen considerably.”

Without a strong El Niño influence, climate forecasting for spring (April through June) is more challenging, but NOAA’s Climate Prediction Center says odds currently favor wetter-than-average conditions in coastal sections of the Southeast; warmer-than-average temperatures across the western third of the nation and Alaska; and below-average temperatures in the extreme north-central and south-central U.S.

Rockewell Aero Commander

The Rockwell Aero Commander (AC-500S) is one of the aircrafts used by NOAA’s National Hydrologic Remote Sensing Center to collect snow data to develop accurate flood forecasts.

High resolution (Credit: NOAA)

Meteorologists and hydrologists with the National Weather Service issue timely and accurate flood forecasts and warnings from local weather forecast offices and regional river forecast centers across the nation. They constantly monitor precipitation, temperature, snowpack and waterway levels using a network of gauges, some of which are operated by vital partners such as the U.S. Geological Survey, and using NOAA aerial surveys of snowpack and its water content.

The National Weather Service provides a suite of decision support services ranging from direct briefings with emergency management agencies at all levels to its graphical Advanced Hydrologic Prediction Service available at weather.gov/water.

This is also national Flood Safety Awareness Week. Floods are the deadliest weather phenomena — claiming an average of 100 lives annually. Many of these deaths occur in automobiles and are preventable. If confronted with a water-covered road on foot or in an automobile, follow National Weather Service advice: Turn Around, Don’t Drown.

NOAA understands and predicts changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.