U.S. Spring Flood Forecast: No Widespread Major Flooding Expected
Though the calendar says it's spring, the latest 10-day forecast from the GFS model calls for winter-like weather over the snow-covered northern tier of states in the U.S. through March 26, followed by a slow warm-up. No heavy rainfall events capable of triggering widespread major flooding are predicted through the end of March. A shift to a less winter-like pattern is in the offing for the first week of April, when the flood risk will rise. This weather pattern will put rivers in approximately half of the continental United States at risk of minor or moderate flooding this spring, NOAA said on Thursday in their annual spring flood risk forecast. The highest flood threat is in the southern Great Lakes region, due to above-average snow pack and a deep layer of frozen ground. The unusually long and severe winter in the northern tier of the U.S. from Montana eastward to northern New England has resulted in much more ice formation on rivers than usual, and there is a greater than usual chance of ice jam flooding, caused when a rise in river levels due to melt water run-off or rain causes a sudden break-up of river ice. Fortunately, no widespread major flooding is expected in the U.S., though a deep layer of frozen ground and significant river ice throughout the northern tier of states may cause localized major flooding. The flood risk is highly dependent on the amount and timing of future rainfall, and the rate of snow melt this spring. There are a number of areas at risk of moderate flooding:
Mississippi River between Davenport, Iowa and Burlington, Iowa
Illinois River between Beardstown, Illinois and Henry, Illinois
Red River of the North between eastern North Dakota and northwest Minnesota
Souris River in North Dakota
Western South Dakota
Southern Lower Michigan
Figure 1. The NOAA spring flood forecast shows a large portion of the country is at risk of minor to moderate flooding, but there are no areas at high risk of major flooding. Image credit: NOAA Spring Flood Forecast.
Flood categories are defined by NOAA as follows:
Minor Flooding: Minimal or no property damage, but possibly some public threat (e.g., inundation of roads).
Moderate Flooding: Some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations.
Major Flooding: Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.
Video 1. On March 20, 2014, NOAA's National Weather Service issued its Spring Outlook, covering flooding, drought, temperature, and precipitation through June.
Have a great weekend, everyone!
Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
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