NOAA scientists predict major flooding across most of the United States, due to record rainfall and snow pack this winter. La Niña continues through June 2008, weakening.

This March, meteorologists and climatologists from the National Oceanic and Atmospheric Administration (NOAA) met to discuss the Spring 2008 Outlook, a 3-month forecast on weather and climate. NOAA scientists paid special attention to the urgent issue and potential for natural disaster, predicting major flooding across many parts of the United States. NOAA urged communities to stay alert, and prepare for flooding and a wet spring.

NOAA Predicts Major Flooding

Scientists expect more rain and melting snow to increase the probability of major flooding this spring, which has already been seen in the Mid-west during the month of March. Record rainfall and snow pack have already been recorded in the West, regions of New England and the Rocky Mountains.

NOAA predicts above-average flooding conditions for the following regions:

• Mississippi River basin
• Ohio River basin
• Lower Missouri River basin
• Widespread flooding in Pennsylvania, New Jersey, New York and all of New England
• Possible flooding for most of the West, including Colorado and Idaho, where “150 – 200 percent of average water contained in snow pack” could cause major flooding

U.S. Drought Outlook

NOAA scientists also predicted some improvement for the drought regions of the Southeast, yet water supply is still low. The Southeastern United States recorded near-average rainfall during the winter. However, La Niña conditions will continue to affect the area, with below-average precipitation predicted for spring.

Other predictions for the months of April, May and June include above-average temperatures in the West, the South and Alaska, based on long-term trends. Below-average precipitation is forecasted for the Southwest, a region already experiencing continued drought conditions.

A Moderate La Niña Continues

Continuing this spring, a moderate La Niña will bring above-average precipitation to many areas. Strong La Niña conditions brought above-average snowfall to many parts of the West this past winter. A moderate La Niña will continue into June, becoming weaker as the summer approaches.

Factors for Climate Outlook

Meteorologists and climatologists evaluate many factors when making seasonal climate outlooks. Factors include:

• La Niña or El Niño conditions in effect, using atmospheric and oceanic measurements of ENSO, or El Niño Southern Oscillation
• Trends – 10 year mean temperatures, 15-year mean precipitation, and 30-year climatology period
• Patterns of oscillation - measuring surface air pressure across oceans or long-term global climate patterns – Several oscillations or patterns are observed and measured including the Madden Julian Oscillation also known as the Tropical 30-60 Day Oscillation, the North Atlantic Oscillation and the Pacific North American Pattern
• Anomalies – any departure from norms
• Forecast Models - various means of calculating forecasts using computer models

To compare these predictions with previous seasons, read Climate Predictions Winter 2008.