Contact: Randee Exler FOR IMMEDIATE RELEASE
3/18/97
More of the country is likely to see flooding this year than in any year in the past decade, according to National Oceanic and Atmospheric Administration hydrologists who released the annual Spring Hydrologic Outlook in Washington, D.C., today.
With the high prospect of severe flooding in the upper Midwest and significant probabilities for some flooding in the West; the Mississippi, lower Missouri and Ohio valleys; and in parts of the Southeast, officials with NOAA's National Weather Service stressed the need for people to know what to do to protect themselves during flood events.
"We're very concerned that people recognize the dangers of floods and flash floods and take appropriate action," said Elbert W. Friday Jr., NOAA assistant administrator for weather services. "During the recent flooding in the Ohio river basin, more than 20 people lost their lives. Many people perished in vehicles, and most of these fatalities occurred in areas that were under flash flood and/or flood warnings. In many cases, the loss of life was preventable."
"The Red River of the North in North Dakota and Minnesota and the James River in South Dakota could see record flooding," said Frank Richards, chief of the NWS Hydrologic Information Center in Silver Spring, Md. "Snow cover in this area has unusually high water content. In addition, flooding is forecast to be widespread in the eastern Dakotas, southern portions of Minnesota and Wisconsin, and northern Iowa. As a result of inflow from so many tributaries, minor to moderate flooding is a virtual certainty on the lower Missouri and on the Mississippi rivers."
To the west, there is also considerable concern for spring flooding in the northern and central Rocky Mountains, particularly in Idaho and parts of Montana, Wyoming, Utah and Colorado, as snowpack totals are significantly above average. Locations on the lower Milk River in northeast Montana are expected to reach record levels. Much of Washington and northern Oregon also have exceptional snowpacks and are in jeopardy of spring flooding.
While deep snow in the central and southern Sierra threaten the possibility of snow melt flooding in western Nevada and the Sacramento and San Joaquin River drainages in California, six weeks of generally dry conditions have significantly reduced the flood risk in much of the far West.
Other areas of elevated risk for spring flooding include the Great Lakes region and much of the Southeast from eastern Texas through South Carolina, excluding Florida and southern parts of Alabama and Georgia.
"Large accumulations of snow can be a key factor in springtime flooding," said Richards, "but the degree of flooding depends not only on snow cover but also on how saturated the ground is already, depth of ground frost, and how quickly or slowly frozen rivers thaw, accumulated snowpacks melt, stream levels, and, most importantly, future precipitation. Under almost any scenario, significant flooding is likely on the Red River of the North and the lower James River."
Substantial snow fell during the winter across north-central and western sections of the United States. As this snow begins to melt, the potential for flooding exists across these areas. Heavy rainfall during February and early March caused devastating flooding in the Ohio Valley and residual flooding continues across portions of the Southeast, the middle and lower Mississippi Valley and the Great Lakes regions. These wet conditions create the possibility of continuing flooding if spring rains are heavy in these areas.
Much of the areas of the country that saw heavy precipitation and significant snowpack buildup during most of the early part of the Water Year (which began Oct. 1, 1996, and ends Sept. 30, 1997) have received subnormal precipitation since the end of January. This aided in the effort to draw down reservoirs to provide water storage capacity in the West. Many reservoirs had filled to very high levels from earlier precipitation and snow melt conditions that led to devastating flooding along the West Coast over the Christmas-New Year's holidays. Only Southwest desert areas had subnormal precipitation throughout the winter. During February, however, the middle third of the nation saw the passage of several very wet storm systems, and accumulated a widespread area of more than 150 percent of normal precipitation.
The annual Spring Flood Outlook for the nation is a compilation of flood outlooks prepared by the NWS river forecast centers and weather forecast offices. NWS hydrologists and meteorologists work with federal, state and local agencies to gather snow, streamflow, soil moisture and river ice measurements, and combine that information with rainfall data, and short- and long-term weather forecasts to determine the likelihood of flooding throughout the United States.
For complete information in the National Spring Hydrologic Outlook, visit the National Weather Service web site at: http://www.nws.noaa.gov/oh/hic/nho. For sidebar story ideas on topics such as flood safety or advanced forecasting techniques, visit the NWS public affairs web site at: http://www.nws.noaa.gov/pa/seasonal/index.html