United States: Water deficits persist in the Northeast, surpluses in Upper Midwest

October 21, 2016

The Big Picture
The 12-month map (below) indicates that water deficits ranging from moderate (5 to 10 years expected frequency) to exceptional (greater than 40 years) are forecast for the US Northeast, especially in New England, Long Island, Pennsylvania and western New York extending to Ohio and West Virginia; and the South, especially Alabama and Georgia and across their shared borders with Tennessee and North Carolina. Deficits of somewhat lesser severity are forecast for western Oregon and Northern California, which could be particularly severe west and south of Lake Tahoe. A patchwork of both red and blue tones with occasional purple tones covers the Rocky Mountain States on the map, indicating a forecast of deficits, surpluses, and isolated areas with both conditions.

Surpluses are forecast in western Wisconsin, southeastern Minnesota into northern and eastern Iowa, with exceptional severity in northeastern Iowa. Exceptional surpluses are also forecast along North Carolina’s northeast coast. Surpluses of varying severity are forecast near Abilene and near Big Bend National Park in Texas; along Idaho’s southern border; the western half of the island of Hawaii; and in Alaska from Bristol Bay north through the Nushagak River watershed.

Impacts
Flooding from Hurricane Matthew killed more than two dozen people (paywall) in five states across the southeast US, with the majority of deaths reported in North Carolina. Three thousand people were in shelters, 770,000 homes and businesses were without electricity (paywall), and parts of Interstate 40 and Interstate 95 were closed. Floodwaters threatened even inland upriver towns in North Carolina, surpassing some records set by Hurricane Floyd in 1999. Hundreds of residents of Lumberton fled as the Lumber River rose two feet above its previous record. Officials from the state Department of Environmental Quality are now preparing to dispose of thousands of drowned livestock (paywall) carcasses from flooded factory farms in the region.

Louisiana will receive $437.8 million from the federal government in emergency aid for victims of August flooding. The funds will be distributed primarily in Ascension, East Baton Rouge and Livingston parishes to victims with severely damaged homes and little or no flood insurance. The unusually high rainfall in August was a mixed blessing for sugar producers, increasing tonnage from this season's harvest but delaying or preventing cane planting for the 2017 season.

Flooding in western Wisconsin in late September has caused millions of dollars in damages, officials estimate, and resulted in two deaths. Downtown Gays Mills on the Kickapoo River was under water and Highways 131 and 171 were closed.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail.

As seen in the October through December map oranges and reds – indicating water deficits – continue to dominate much of the northeastern US, though the expanse of exceptional deficits is expected to shrink. Primarily moderate (5 to 10 years) to severe (10 to 20 years) deficits are forecast in Virginia, West Virginia, Ohio, Kentucky, Tennessee, western North Carolina, South Carolina, Georgia, Alabama, Mississippi, Arkansas, northern Louisiana, Oklahoma, East Texas, Arizona, Southern California, and along the Missouri and Yellowstone Rivers. Severe to exceptional deficits are expected in Alaska’s Far North near Barrow, the eastern North Slope, and the borough of Southeast Fairbanks.

A large block of blue tones – indicating a forecast of moderate to exceptional surpluses – follows the Upper Mississippi River and encompasses southern Minnesota, much of Wisconsin, and northern Iowa. Surpluses are also forecast during this period for: northern coastal areas of North Carolina; Nebraska; northeastern Nevada; isolated pockets in southern Wyoming and on Idaho’s southern border; Texas near Abilene and near Big Bend National Park; the western half of the island of Hawaii; and a large swath of Alaska from Bristol Bay north to the Interior.

From January through March surpluses will continue to emerge in Wisconsin, southern Minnesota, throughout Iowa, Michigan’s Upper Peninsula, and southwest Alaska. Surpluses will also emerge in the northern portion Michigan’s Lower Peninsula, in eastern New York, northern Indiana, Nebraska, and the Rocky Mountain States. Deficits across the US are forecast to diminish greatly. Moderate to severe deficits will persist from southern Montana into northern Wyoming, and in aforementioned areas of Alaska. Moderate deficits will persist in West Virginia, North Carolina, South Carolina, and Florida, and along the Canadian River through the Texas Panhandle.

The final quarter of the forecast period (Apr-Jun 2017) indicates moderate water surpluses throughout the Rocky Mountain States, in Nebraska, southern Minnesota, Iowa, and along the Platte and Missouri Rivers. Mostly moderate deficits are forecast to return to the US Northeast, and will persist in other parts of the country.

(It should be noted that forecast skill declines with longer lead times.)