United States: Exceptional water deficits to retreat in Northern Plains States

29 August 2017

The Big Picture

The dark red block covering eastern Montana in the 12-month forecast above indicates exceptional water deficits in the state and severe to exceptional deficits in the neighboring states of North Dakota, South Dakota, and into northwestern Minnesota. Moderate deficits are forecast for parts of western Iowa and in Nebraska.

Further west, Utah, Nevada, and California are expected to see deficits ranging from moderate to severe along with scattered small pockets of exceptional surplus in northern Nevada and northwestern Utah, and both deficits and surpluses in central California into western and northern Nevada and northwestern Utah. Extreme to exceptional surpluses are forecast along the Snake River and in the Salmon River Mountains in Idaho, and along the Columbia River separating Washington and Oregon. Both deficits and surpluses cover much of the remaining Northwest, including Idaho, much of Oregon, Washington, and far western Montana.

Some mild water deficits are forecast in the US Southeast from eastern North Carolina through southeast Georgia, and also west of the Brazos River in Texas.

Surpluses ranging from moderate to occasionally extreme are expected in: Wisconsin, northern Illinois, northern Michigan, central Indiana, New York, and Vermont. Surpluses of equal intensity are forecast along the Gulf in southern Louisiana, Mississippi, and Alabama; and, along the Arkansas River through western Kansas into Colorado, and in southern Colorado.

Outside the contiguous US, deficits are forecast for Alaska and western Puerto Rico, and surpluses are forecast for Hawaii.

Impacts
Hurricane Harvey struck the US Gulf Coast in late August, creating what the National Weather Service described as an "unprecedented" weather event, dumping more than two feet of rain in the Galveston-Houston area, with predictions totaling 50 inches. Five deaths have been reported; schools, airports, and offices in Houston were ordered shut; and more than 30,000 people are expected to be placed in shelters. The US Army Corps of Engineers issued orders for a planned release from two reservoirs in Houston, and President Trump authorized a national disaster proclamation for Texas, releasing federal emergency funds.

The National Flood Insurance Program, now nearly $25 billion in debt, faces its next reauthorization - as required every five years by Congress - in September.

Drought in the US Northern Plains has withered pastureland, devastated wheat production, and spurred massive wildfires. Many communities in Montana's Missouri River basin are experiencing their driest growing season on record and the USDA projects that 2017/18 wheat supplies will be down 21 million bushels. The Lodgepole fires burned over 220,000 acres in Montana and destroyed 16 homes in July, contributing to one of the worst fire seasons Montana has seen in years.

Both drought and fire have compromised grazing land, and cattle ranchers facing fodder costs that have risen from $100 to $180 for a ton of hay are turning to North Dakota's first hay lottery for relief, giving them a chance to win a semi-truck load. Officials estimate that Montana's Lodgepole fires destroyed 1,400 miles of livestock fencing, the replacement cost of which is $15 million. Adding to the financial burden is the loss of livestock and loss of income from the forced early sale of reproductive stock.

Roughly half of Iowa's farms are suffering from drought as well, in a path from the northwest through the southeast of the state, with expected corn yields of 25 to 80 bushels per acre on fields that normally average 180 bushels. Crop insurance will cover about 85 percent of the losses.

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

Though observed conditions through July show exceptional deficits in the Northern Plains States, the forecast maps from August 2017 through April 2018 indicate significant retreat and even a transition to surplus in early 2018. However, in the near-term moderate deficits are expected to persist in southwestern North Dakota, northern Minnesota, Iowa, Nebraska, as well as in northeastern Texas through October. Deficits of greater severity will emerge in Maine near Portland and in the north and east.

Surpluses in the Gulf region will persist, remaining extreme in southern Mississippi, and decreasing slightly in severity in southern Louisiana and in extent in Alabama. Surpluses observed in prior months in the Great Lakes states will diminish, and surpluses in Virginia and North Carolina will transition to mild deficits. Both deficits and surpluses are forecast for the West Coast into the northern US Rocky Mountain states.

From November through January primarily moderate water surpluses will re-emerge in most of the Great Lakes States and in the Ohio River Valley. Pockets of surplus will continue to emerge in Idaho and surrounding states, which may reach exceptional intensity west of Pocatello. Deficits in the southern states of the Eastern Seaboard are expected to ratchet up slightly to moderate intensity and extend through Florida.

The forecast for the final months of the forecast period – February through April – indicates near-normal conditions in the eastern US and surpluses in the Rocky Mountain States and along the Missouri, Yellowstone, Platte, and Arkansas Rivers.

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

Note on Administrative Boundaries
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