United States: Water surpluses forecast for MT, NE, IA, WI, & PA

28 September 2018

THE BIG PICTURE
The 12-month forecast ending May 2019 indicates exceptional water deficits in the Pacific Northwest, and deficits reaching extreme to exceptional intensity in Colorado and Utah; moderate to extreme deficits are forecast for Northern California and northern Nevada. Deficits are forecast for the US Northeast – including extreme pockets – as well as for northern Minnesota, and Louisiana into eastern Texas. Primarily moderate deficits are expected in the Ohio River Basin. Intense surpluses are forecast for Montana into eastern Idaho. Surpluses of varying intensity are forecast for: the Black Hills along the South Dakota/Wyoming border; northern Nebraska; northern Iowa into southeastern Minnesota; southern Wisconsin into northern Illinois; northern Wisconsin into the western portion of Michigan’s Upper Peninsula; eastern Pennsylvania through northern Virginia; and central Florida.

Outside the contiguous US, surpluses are forecast for Hawaii. In Alaska, surpluses are forecast in the northwest; in the southwest from Bristol Bay well into the interior; and in the southeast in the upper reaches of the Copper and Susitna Rivers. Deficits are forecast around Anchorage. In Puerto Rico, moderate to severe deficits are expected throughout the country.

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

NOTE: The WSIM model makes use of seasonal temperature and precipitation forecasts produced by the U.S. National Oceanic and Atmospheric Administration (NOAA) Climate Forecast System Version 2 (CFSv2). These forecasts predict broad temperature and precipitation patterns, but do not effectively predict singular events such as tropical storms. Detailed outlooks and analyses of tropical storms are available from NOAA National Hurricane Center.

The near-term forecast through November indicates that deficits which have dominated much of the West and Southwest will downgrade considerably. Moderate to severe deficits are expected in the Pacific Northwest and some moderate deficits in California. Severe to exceptional deficits are, however, expected along the Arkansas River through Kansas and Colorado, western Colorado, and northeastern Utah. Deficits will be severe along the Canadian River through Oklahoma and the Texas Panhandle. Intense deficits are also forecast in the Northeast and may be exceptional in northeastern New York and northern Vermont. Moderate deficits are expected in the Ohio River Valley, northern Minnesota, eastern Kansas, and pockets of Missouri, eastern Texas, and the South Atlantic States.

Surpluses reaching exceptional intensity are forecast for Montana, the Black Hills along the South Dakota/Wyoming border, and northern Nebraska, with conditions of both surplus and deficit in western Montana as transitions occur. Surpluses ranging from moderate to extreme are forecast for Iowa into southwestern Minnesota; Wisconsin’s southern third and far north, reaching into central Wisconsin and the western region of Michigan’s Upper Peninsula; and eastern Pennsylvania into New York, Maryland, and northern Virginia.

From December through February, deficits will continue to decrease nation-wide becoming merely mild overall but with more intense deficits lingering in north-central Utah, Colorado, and along the Arkansas and Canadian Rivers. Moderate deficits will persist in northeastern Minnesota. Nearly normal conditions are expected in the Ohio River Valley, much of the Deep South, and the Lower Mississippi region.

Intense surpluses will persist in northern Nebraska, the Black Hills, and Montana, and will re-emerge in western Montana. Pockets of moderate surplus will emerge in Idaho, Oregon, and northeastern Nevada. Some scattered, primarily mild surpluses will emerge in the Southwest. Surpluses will persist in Iowa and surrounding states as previously described and will emerge across a central band in Michigan’s Lower Peninsula. Surpluses in Pennsylvania and surrounding states will moderate. Moderate surpluses will emerge in southern Georgia into northern Florida, and some mild surpluses will emerge scattered in the Lower Mississippi region.

The forecast for the final months – March through May – indicates the emergence of widespread, primarily moderate deficits east of the Mississippi, and surpluses in the Rockies, along many rivers in the center of the country, and Oklahoma, Texas, the Rio Grande, and California.

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

IMPACTS
As Category 4 Hurricane Florence approached the mid-Atlantic coast this month, over 1 million people were put under mandatory evacuation orders. President Trump issued an emergency declaration for North and South Carolina ahead of the storm, which made landfall as a Category 1 Hurricane on September 14, pelting the Carolinas with up to 40 inches of rain causing widespread flooding. Florence killed at least 48 people across North Carolina, South Carolina, and Virginia. Moody’s Analytics estimated total damages between 17 and 22 billion dollars.

Hurricane Lane, a Category 5 hurricane at its peak, broke apart by wind shear before the system hit Hawaii, unloading up to three feet of rain in some areas, as the United States’ second-rainiest tropical cyclone since 1950. Over 800 people evacuated their homes, and military ships vacated Pearl Harbor ahead of Lane’s approach. Flood damages to public works in Hawaii County are estimated at $20 million. Hundreds of homes and dozens of businesses in the county sustained damages, though none were destroyed. One person died in the hurricane’s aftermath while rescuing a dog from a swollen stream in Kauai.

High-speed gusts from Lane knocked out power for thousands of Maui customers for at least two days, and fueled a brush fire into fiery tornado-like whirlwinds that burned 2,000 acres of land and destroyed 30 vehicles and 21 buildings. One person was hospitalized for burns.

A wildfire forced the evacuation of dozens of homes and the closure of Interstate 5 in drought-stricken Northern California early this month. The Delta Fire burned 62,504 acres as of late September.

Research released last month found that lack of summer rain and extended duration of droughts - not higher temperatures and early snowmelt - are leading to larger and more severe forest fires in the western United States.

The United States Drought Monitor reported last month that over half the country is abnormally dry or in a drought.

Though Texas and Mexico share agreements for water flowing through the transboundary Rio Grande, questions loom over what will happen when the Rio Grande runs dry, as Texas and Mexico have no agreement governing their 15 shared underground aquifers. Meanwhile, the United States Supreme Court announced last month that the case between Texas, New Mexico, and the US government over groundwater associated with the Rio Grande will go to trial no later than the fall of 2020.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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