FORECASTERS WARN OF FLOOD POTENTIAL THROUGH SUNDAY

February 19, 2003 — On the heels of last weekend’s major East Coast snow storm, forecasters at the NOAA National Weather Service are eyeing the possibility that another round of storms will dump significant rain from Texas into the Tennessee Valley, the Mid-Atlantic and Northeast regions beginning Friday. Localized flooding is possible in Texas, parts of Arkansas, Louisiana and Mississippi. Serious flooding is a concern in parts of Kentucky and Tennessee. Forecasters said the risk of flooding is probably greater there than in the Mid-Atlantic region. (Click NOAA satellite image taken Feb. 17, 2003, at 10:33 a.m. EST for larger view of the storm that struck the eastern USA inundating many states with snow. Please credit “NOAA.”)

“At this time, we do not expect a repeat of the disastrous river flooding of late January 1996,” said Frank Richards, a senior NOAA hydrologist at the NOAA National Weather Service. “However, where storm drains are now snow-clogged, serious urban flooding could be a problem unless concerted efforts are made to open storm drains.”

Last weekend, a major storm swept though upper portions of the Tennessee Valley and the southern Ohio River Valley, the Mid-Atlantic and Northeast. As a result, there was widespread flooding in northern Alabama, portions of Tennessee, Kentucky, Virginia and West Virginia. Another storm system this weekend could produce an additional 2-3 inches of rain that could cause significant rises in streams that are already running high. The potential exists for serious flooding in Kentucky and Tennessee starting on Friday. (Click NOAA image for larger view of snowfall totals in the USA from Feb. 17-19, 2003. Please credit “NOAA.”)

Currently, forecasts for the coming weekend indicate as much as 2-3 inches of rain could fall over areas of the Mid-Atlantic with lesser amounts in coastal New England. While this could cause flooding, particularly in the Mid-Atlantic, major river flooding is not anticipated at this time, Richards said. “Significant urban flooding may cause serious damage because it will affect areas with high population density and susceptible infrastructure, for example, basement flooding, increased weight on snow-covered roofs.”

He said there are reasons that will make a repeat of 1996 flooding unlikely in the Mid-Atlantic, including:

• A deep, fresh snow pack, which will act like a sponge, absorbing an inch or more of rain, reducing runoff and mitigating river flooding.
• While rains will be accompanied by warmer temperatures, snow melt is not likely to match the conditions of 1996. In 1996, snow melt made a significant contribution to the runoff that caused flooding. The unprecedented snow melt largely was due to very moist air condensing on the snow surface and releasing heat. In 1996, dew points were in the mid-50s. Dew points this weekend are not likely to exceed the mid-40s, substantially reducing snow melt potential, compared to 1996.
• The 1996 rain event was caused by a series of low pressure centers and warm air that was in place for a prolonged period. Current forecasts indicate the storm will move more rapidly than 1996 and cooler air will reduce snow melt once the storm moves out.

The NOAA National Weather Service advises the public to keep ahead of the storm by listening to NOAA Weather Radio and commercial radio and television broadcasts for the latest information on this system and the issuance of winter storm watches, warnings and advisories in order to take proper precautions.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources. NOAA is part of the U. S. Department of Commerce.

Relevant Web Sites
Animation of the Predicted Path of the Storm

NOAA Storm Watch

NOAA Significant River Flood Outlook

NOAA Floods Page

NOAA Hydrologic Information Center — includes National Flood Summary

NOAA River Forecast Centers

U.S. Hazards Assessment

U.S. Snow Monitoring

NOAA Winter Storm Preparedness Guide

Media Contact:
John Leslie, NOAA National Weather Service, (301) 713-0622