United States: Exceptional water deficits forecast AR, MO; surpluses in ID

27 March 2017

The Big Picture

The 12-month forecast through November 2017 (above) shows the predominance of water deficits in the eastern half of the county and surpluses in Idaho, California, and scattered throughout the Pacific Northwest. Exceptional deficits are forecast in northern Arkansas, and severe to extreme deficits are expected in neighboring Missouri and Illinois to the north along with eastern Oklahoma, northeastern Texas, and Louisiana. Primarily moderate deficits are expected in states to the near east including Indiana, Ohio, Kentucky, Tennessee, Mississippi, and Alabama. More intense deficits are forecast along the Eastern Seaboard ranging from moderate to severe from southern Pennsylvania through Florida. Severe deficits are forecast for northern Michigan and moderate deficits are forecast for the US Northeast.

Exceptional surpluses are forecast for nearly all of Idaho, parts of northern Nevada, and Central California into western Nevada. Both deficits and surpluses are expected in northern California. Surpluses of lesser severity are forecast in eastern Washington and eastern Oregon, and moderate deficits are predicted in the western regions of both states. Some moderate surpluses are forecast in: the Southern Rockies and along the Rio Grande and the Canadian River through New Mexico; central Arizona; and, southwestern Minnesota into northeastern Iowa.

Outside the contiguous US extreme surpluses are forecast for the western portion of the island of Hawai’i and scattered deficits are forecast for Alaska.

Impacts
The Pineapple Express - an "atmospheric river" - pounded Northern California, challenging levees and bringing out the pontoon boats. The region has received more than twice the normal amount of rain and snow this winter after a five-year drought, with runoff surging into the Central Valley. Flows were released from the Don Pedro Dam for the first time in nearly two decades.

Over the years flood control projects - including a $5 billion bond issue approved by state voters - have offered protection to nearly 500,000 residents of the state capitol, Sacramento, and to smaller cities in the Valley. In rural areas, however, farmers are expected to maintain the levees, and February's drenching brought tractors out round-the-clock along the San Joaquin River to prevent damage from a 30-foot break in one levee in the chain of 1,600 miles of Valley levees. California's governor has asked lawmakers to approve $387 million to speed up flood control projects in the region. Flood experts from the California Public Policy Institute estimate long-term costs of state-wide levee maintenance and improvement at $20 billion.

Even Seattle, Washington - where the city's reputation for rainfall has inspired many local jokes - has seen more than its normal share of wet weather recently - 200 percent more by mid-March according to a National Weather Service meteorologist. Flood warnings were in effect for many rivers in the state, flooding in Yakima closed some city streets and altered transit routes, and Gov. Jay Inslee declared a state of emergency in 20 counties.

Heavy rains in Hawaii closed schools, roads, and many public facilities including Waimea Valley nature park where a tractor washed away, a park roadway was damaged, and the water level in a park stream - normally 1 foot - rose to 12 feet. A Brown Water Advisory was issued for Oahu, Kauai and Maui, warning residents of possible contamination from runoff. Excess precipitation translated to heavy snowfall in the state's summits where eight inches of snow closed access to Mauna Kea, giving Hawaii more snowfall than Chicago or Denver.

Drought-fueled wildfires across US prairie states have killed 7 people, burned 1 million acres, and left an unknown number of livestock dead in Kansas, Oklahoma, and Texas. Firefighting estimates run into the millions of dollars. "This is our Hurricane Katrina," said one agricultural extension agent from Kansas State University.

Three and a half months after fire swept through Gatlinburg, Tennessee hazmat services have detected high levels of contaminants in rivers and streams in the area. There is also increased potential for mudslides on Ski Mountain from the destabilization of slopes due to burned trees and underbrush.

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

The March through May map indicates a retreat of exceptional deficits except in Arkansas, Missouri, and western Illinois. However, moderate deficits are forecast to emerge throughout much of the US east of the Mississippi River and may reach extreme intensity in Virginia and West Virginia. Moderate to extreme deficits are also expected in Kansas, eastern Oklahoma, and eastern Texas, and southern Arizona. A pocket of exceptional deficit is forecast in the far north of Michigan’s Lower Peninsula.

Primarily exceptional surpluses are forecast for Idaho and northern Nevada. Surpluses are predicted for the Pacific Northwest ranging from moderate to exceptional, with exceptional surpluses along the Colombia River. Moderate to exceptional surpluses are also forecast for Central California into western Nevada, and in western Colorado. Moderate surpluses are expected in southern Minnesota, northern Iowa, western Wisconsin, and southeastern New York. Moderate surpluses are also forecast along the Missouri River, which may be more severe in Montana, and along intermittent stretches of the Rio Grande.

From June through August exceptional deficits are expected to dissipate but moderate deficits will continue to emerge in the eastern half of the country, and more severe deficits will persist in northern Arkansas, southern Missouri, and Virginia. Exceptional surpluses in Idaho will recede to isolated pockets. Moderate surpluses are forecast in nearby western Wyoming and eastern Oregon. Both deficits and surpluses are expected in California and northern Nevada.

The final months of the forecast – September through November – show a retreat of deficits in the East and the emergence of moderate deficits in the Pacific Northwest

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