1 Historic Spring Flooding Ohio River Valley and Mississippi River Ernie Wells Hydrologic Services Division

2 Snow Water Equivalent Substantial stored water in the snow pack represents significant flooding potential in the North Central and Northeast as the spring thaw begins March 18, 2011

3 National Hydrologic Assessment Spring 2011 – Issued March 17, 2011

4 River Observations May 3 Observations of major to record crest levels in the Ohio River Valley along the Mississippi River

5 Observed Precipitation April 18, 2011 – May 2, 2011 During the previous 2 weeks, a broad area of Central US received inches of precipitation; 600% of normal precipitation

6 Forecasted Precipitation May 2, 2011 – May 7, 2011 During the next 5 days, a broad area of Central US received inches additional rain (much has already fallen)

7 Extended Range Forecasts 6-10 Day Forecasts Precipitation (May 8-12)Precipitation (May 10-16) 8-14 Day Forecasts

8 Hydrologic “Perfect Storm” WFO Paducah, KY Confluence of Ohio River and Mississippi River

9 Hydrologic “Perfect Storm” Cairo, IL - Confluence of Ohio River and Mississippi Historic levee break at New Madrid relieving flood crest at Cairo

10 Hydrologic “Perfect Storm” WFO - Memphis Crest Moving downstream – expect flooding through June

11 River Forecasts May 3 – next 48 hours Short-term streamflow forecasts predict minor to major crest levels in the Northeast, Ohio River Valley, and Alabama and Mississippi