United States: Water deficits MO, OK, AR; surplus ID, NV, UT

31 January 2017

The Big Picture
The 12-month forecast through September 2017 (above) indicates widespread extreme to exceptional water deficits across the South, as well as widespread deficits of lesser severity in the Northeast and in the Ohio River Valley. Deficits may be particularly severe in Arkansas, Louisiana, Alabama, and northern Georgia. Surpluses ranging from moderate to exceptional are forecast in Idaho, northeastern Nevada, and northwestern Utah. Surpluses of lesser severity are forecast for southern Minnesota, northern Iowa, and southwestern Wisconsin.

Outside the contiguous US exceptional surpluses are forecast in Hawaii, moderate deficits in western Puerto Rico, and moderate to extreme deficits in west-central and eastern Alaska.

Impacts
A series of powerful snowstorms pummeled Idaho with accumulations up to four feet, collapsing hundreds of roofs in Washington County and prompting the state’s governor to declare a state of emergency there and in neighboring Payette County. One death was reported when a residential roof collapsed, and National Weather Service officials estimate that in western Weiser the weight of the snow reached 39.5 pounds per square foot. Onion prices jumped from $3.50 to $6.50 for a 50-pound bag after 20 storage facilities were crushed.

Elsewhere, snow weight crushed a lumber mill in Oregon, a sports complex in Alaska, and a conference center in Colorado.

So much precipitation – both rain and snow – have fallen near Lake Tahoe, California that the lake surface has risen by nearly a foot since January 1, according to the National Weather Service in Reno. Snowpack in the Sierra Nevada range was 161 percent of normal in mid-January. Evacuations were ordered in Sonoma County, California as the Russian River rose, and in Reno, Nevada as the Truckee River crested. Rain and snowmelt caused mudslides, avalanche warnings, and power outages in many parts of Nevada and Central and Northern California.

A national fire advisory has been issued for Oklahoma – the first ever for the state. Several years of drought in the state have increased wildfire potential, and dozens have been reported over the last several months. Eight counties in southeastern Oklahoma are in extreme drought according to the US Drought Monitor.

Drought throughout the southeast has impacted hay stock assessments – the USDA January Crop Production report states that stocks are down 34.4 percent in Alabama, 13.6 percent in Georgia, and 5.3 percent in Mississippi.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail. What is readily apparent in the January through March map is the transition to normal, shown in white, for some regions in the eastern US. However, extreme to exceptional water deficits are forecast for Missouri, Oklahoma, Arkansas, and southern Iowa, as well as in a line extending northeast from Mississippi through Alabama, northern Georgia, western South Carolina, western North Carolina, Virginia, Maryland, and Pennsylvania. Deficits of equal severity are forecast for the northern portion of Michigan’s Lower Peninsula, western Illinois, and central Colorado. Deficits are also forecast for east-central Indiana into Ohio, eastern Texas, and Florida.

A large block of exceptional surplus is forecast during this period for southern Idaho, northeastern Nevada, and northwestern Utah. Moderate to extreme surpluses are forecast for southern Minnesota, Wisconsin, and northern Iowa. Surpluses of varying severity are expected in California, Oregon, Washington, northwestern Montana and parts of the Missouri River in Montana.

From April through June exceptional deficits are no longer in the forecast, noticeable by the absence of dark red. But moderate deficits along with some severe deficits are forecast across the South in eastern Texas, Arkansas, Louisiana, Mississippi, Georgia, Florida, South Carolina, and North Carolina. Deficits of similar intensity are expected in eastern Ohio, northern West Virginia, Pennsylvania, and scattered throughout the Northeast.

Surpluses are forecast to persist in Idaho and northeastern Nevada, and will emerge in western Wyoming. Surpluses may be exceptional in western Wyoming and in the Snake and Salmon River watersheds in Idaho.

The final quarter of the forecast period – July through September 2017 – indicates moderate deficits in the West and deficits of greater severity throughout the Deep South and Southeast.

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