United States: Extreme water deficits forecast in the Northeast, Southeast (August 25, 2016)

The Big Picture
The 12-month map (below) indicates that water deficits ranging from moderate (5 to 10 years expected frequency) to extreme (20 to 40 years) with isolated instances of exceptional severity (greater than 40 years) are forecast for much of the US Northeast and Southeast, western Oregon, Washington, northern California, Montana, northern Wyoming, western Nevada, northeastern Utah, southeastern New Mexico, and north and southeastern Alaska.

Surpluses are forecast in northwestern Wisconsin, southern Minnesota, Nebraska, the Brazos River Basin and southeastern Texas, western Kentucky, and Hawaii.

Impacts
Flooding has killed at least 13 people in Louisiana and left thousands homeless, with damages estimated at $30 million and climbing. In Livingston Parish 31 inches of rain fell in 15 hours. Across the state more than 30,000 people and 1,400 pets were rescued; 125 cars were stranded on a seven-mile stretch of Interstate 12 near Baton Rouge; farmland was flooded; and shopping centers inundated. Gov. John Bel Edwards declared a state of emergency, and he and his family were evacuated from the Governor's mansion in Baton Rouge when waters began to fill the basement.

A torrential downpour also sent floodwaters swirling through Ellicott City, Maryland, in what one Howard County official characterized as the worst he'd seen in 50 years, including Hurricane Agnes in 1972. Two people died when floodwaters carried their car toward the Patapsco River. Businesses, residential areas, streets, and sidewalks were extensively damaged, and a state of emergency was declared, clearing access to state resources.

As of August 18, the US Drought Monitor classified 57 percent of the US Northeast in drought. Mandatory restrictions on outdoor water use are already in place in many Massachusetts towns and the governor is urging conservation of indoor water. Dry conditions have elevated the wildfire risk: 1,000 wildfires have been recorded so far against an annual average of 1,600.

Farmers in Maine, New Hampshire, and Connecticut are struggling to keep crops watered as wells and irrigation ponds dry up.

The 215-foot tall Taughannock Falls in New York's Finger Lakes region has slowed to a mere trickle in the drought and visitors are hiking the dry creek bed instead of nearby trails.

Wildlife officials in Montana have ordered the unprecedented closure of an 183-mile stretch of the Yellowstone River along with hundreds of miles of other waterways in an attempt to stop the spread of a parasite that has already killed thousands of fish. Low water levels and warm conditions add to the stresses on cold-water species; previous outbreaks have receded when water temperatures dropped. The river's closure threatens the area's fishing and tourism economy.

A state of emergency has been declared for 20 counties in Washington state, as wildfires rage in hot, dry conditions. California's scenic Highway 1 was shut down as the "Soberanes Fire" scorched 60,000 acres, destroyed property, and left one person dead. The origin was an illegal campfire, exacerbated by drought and high winds.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail with an overall pattern through October of oranges and reds, indicating water deficits, along with a few expanses of blue-green surpluses. After October, a transition away from severe deficits (10 to 20 years) and the emergence of moderate surpluses (5 to 10 years) is forecast.

Exceptional deficits in the Northeast are forecast to diminish in extent from August through October. However, deficits will remain widespread and severe or extreme in many areas. Moderate to severe deficits are forecast in Ohio, Michigan, Indiana, and Illinois.

In the Southeast, exceptional deficits are forecast to emerge in Florida, and moderate to extreme deficits will continue to emerge in Tennessee, western and southern North Carolina, South Carolina, Alabama, and Georgia. Deficits along the Tennessee River in western Tennessee into northern Alabama are expected to be extreme.

Deficits will also continue to emerge in the Northern Border States during this period, with particular severity along the Missouri and Yellowstone Rivers.

Much of the US West is also forecast to experience deficits ranging from moderate to occasionally exceptional, though many areas may see both deficits and surpluses as conditions transition.

Moderate to extreme water surpluses are forecast to emerge in Wisconsin’s western half, and over the southern border into southeastern Minnesota and eastern Iowa. Surpluses are also forecast for much of Nebraska, and eastern Texas. Severe to extreme surpluses are forecast for the southwest corner of Kentucky.

From November through January widespread deficits are forecast to diminish in extent and severity with the exception of the Missouri and Yellowstone Rivers, and in the Southeast, particularly Florida. Surpluses are expected to diminish considerably in Texas, but persist in Wisconsin, eastern Minnesota, northeastern Iowa, and Nebraska. Moderate surpluses will emerge in Southern California and central Arizona. As deficits in the West recede, some areas of both deficit and surplus will transition to pockets of surplus.

The final quarter of the forecast period (Feb-Apr 2017) indicates water surpluses throughout the Rocky Mountain States, especially along rivers.

Outside the contiguous US, moderate to extreme deficits are forecast for many parts of Alaska through October, which will diminish somewhat after. Moderate to exceptional surpluses are forecast for the island of Hawaii, particularly the western half.

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