Rainfall intensity and location can only be accurately forecast days in the future therefore, flood risk can change rapidly. Heavy rainfall at any time can lead to flooding, even in areas where the overall risk is considered low. The information presented in this report focuses on spring flood potential, using evaluation methods analyzed on the timescale of weeks to months, not days or hours. The flood potential is expected to be above normal for the Upper Yukon, Upper Tanana, and portions of the Copper River basins.īased on the expected spring flood outlook, average hypoxia zones are expected for the Gulf of Mexico and for the Chesapeake Bay. In Alaska, spring ice breakup and snowmelt flood potential is forecasted to be normal for the majority of the state with some exceptions. This is due to a combination of near to below normal snowpack. Over the Northwestern United States as well as the Upper Missouri, Arkansas, and Rio Grande basins, normal to below normal water supply volumes are expected. Above normal snowpacks in the Sierra Nevada, Great Basin, and portions of the Central Rockies will lead to the continued potential for minor to moderate flooding for higher elevation basins in those areas as well as portions of the Upper Snake River.Ĭurrent water supply forecasts in the western United States indicate above normal water supply conditions over California, Nevada, the Great Basin, and the Colorado River due to well above normal snowpacks. Numerous atmospheric river events in the west, combined with near record snowpacks, have led to recent widespread flooding throughout California, including ongoing minor to moderate river flooding. Moderate flooding is expected along the Red River of the North in North Dakota and the James River in South Dakota. This spring season, approximately 146 million people are at risk for flooding in their communities, with nearly 6.4 million at risk for moderate flooding and 1.4 million at risk for major flooding.Īn active winter with above normal snowpack has led to the potential for major flooding along portions of the Upper Mississippi River. NOAA's network of 122 Weather Forecast Offices, 13 River Forecast Centers, National Water Center, and other national centers nationwide assess this risk, summarized here at the national scale. The 2023 National Hydrologic Assessment offers an analysis of flood risk, water supply, and ice break-up and jam flooding for spring 2023 based on late summer, fall, and winter precipitation, frost depth, soil saturation levels, snowpack, current streamflow, and projected spring weather.
#WHATS AN AREAL FLOOD WATCH PDF#
View the PDF version of the 2023 National Hydrologic Assessmentįigure 1: National Spring Flood Risk defined by risk of exceeding Minor, Moderate, and Major Flood Levels.ĭownload the shapefile | Download the layer file (right click and save as) | Download the KMZ fileįor an interactive look at the Spring Flood Outlook, please visit the 2023 Spring Flood Outlook Story Map Journal
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