United States: Water deficits forecast AR, LA, FL, GA, SC, NC, VA

26 April 2017

The Big Picture

The 12-month forecast through December 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. Severe to exceptional deficits are forecast in Arkansas, Louisiana, Mississippi, Alabama, and throughout Eastern seaboard states from Maine through Florida. These deficits may be especially intense in northeastern Arkansas and in Florida, and deficits in the South Atlantics states are expected to be of greater severity than in the Northeast. Primarily moderate deficits are forecast in the Ohio River Valley. Moderate to severe deficits are forecast for Northern Michigan.

Exceptional surpluses are forecast for nearly all of Idaho, parts of northern and western Nevada, and pockets of Central California, central and eastern Oregon, and eastern Washington. Surpluses of varying severity are forecast for western Montana, western Wyoming, northwestern Utah, and much of California from Bakersfield north. Both deficits and surpluses are forecast for central and northwestern California, western Oregon and western Washington.

Outside the contiguous US extreme surpluses are forecast for the western portion of the island of Hawai’i. Moderate to occasionally extreme deficits are forecast for much of Alaska.

Impacts
The US Drought Monitor dated April 18 categorized more than 34 percent of Florida in severe drought, leaving the state in conditions ideal for wildfires. Florida's governor has declared a state of emergency due to the number of wildfires, which have burned 250 percent more area in the first three months of 2017 than during the same period last year. At mid-April more than 100 active wildfires burned across 20,000 acres according the state's Agricultural Commissioner, and more 126,000 acres have burned this year, already surpassing the 5-year average of acreage burned in a single year. Fires forced the Florida State Highway Patrol to close three major roads in central Florida due to poor visibility from smoke, and the Orange County Department of Health issued a warning about respiratory health risk.

Spring rainstorms and flooding in Michigan closed roads in Kalamazoo and left fish swimming in the outfield at Homer Stryker Field, home of the Kalamazoo Growlers baseball team after the Kalamazoo River overflowed. In East Lansing the force of flood waters from the Red Cedar River scrubbed the field surface off at Secchia Softball Stadium, washing it downriver, and left McLane Baseball Stadium and DeMartin Soccer Stadium submerged. Several major freeways were closed in Flint after a storm that knocked out power to several thousand residents and businesses. Flood advisories have been in effect for many Mid-Michigan rivers.

California's Department of Water Resources says that the northern Sierra Nevada has recorded its wettest winter on record - 89.7 inches of precipitation since October. Heavy rain has damaged some produce crops in the state and has sent lettuce prices soaring to $5 a head.

In Idaho a state of emergency was declared in Boise in early April as the Boise River overflowed, fueled by excessive snowpack and exacerbated by recent rainfall. Flow along the river was running abnormally high, hitting 9,030 cubic feet per second. Officials point out that there is currently about 1.85 million acre feet of water in the 2,680-square-mile watershed - about six times more water than space available in the three reservoirs used to control flooding.

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

The April through June map shows the continued emergence of severe to exceptional deficits in the South and South Atlantic states and moderate deficits in the Northeast and Ohio River Valley. Deficits will persist in southern Illinois, Missouri, Arkansas but the extent of exceptional deficits will shrink. Exceptional surpluses are expected to persist throughout Idaho but should diminish considerably in Central California. Deficits ranging from abnormal to exceptional are forecast to emerge throughout Oregon during this period, along with many parts of Washington.

From July through September deficits east of the Mississippi River are expected to decrease in severity leaving moderate or lesser deficits in northern states and moderate, severe, and pockets of extreme deficits in southern states. Moderate deficits may emerge on the Arkansas and Colorado Rivers and moderate to severe deficits in northern Colorado. Scattered surpluses are forecast in eastern Oregon and southern Idaho ranging in severity from moderate to exceptional. Both deficits and surpluses are expected in western Washington, western Oregon, northern Nevada, and western California.

The final months of the forecast – September through November – show a retreat of deficits east of the Mississippi and the emergence of surpluses in central and eastern Texas.

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