UNL Drought Monitor - Week Of 11 September

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The West: Scattered rainfall and reduced temperatures kept conditions from deteriorating this week, but were not sufficient to provide any widespread relief. As a result, few changes in drought classifications were made from the Rockies westward, although recent precipitation was enough to eliminate the area of D3 conditions in west-central Wyoming, and to eradicate abnormal dryness across interior New Mexico.

The Plains: Moderate rainfall (0.5 to 2.0 inches) allowed for some retraction of D0 to D2 conditions in portions of the western Dakotas, but below-normal precipitation for the past several weeks led to the expansion of D0A conditions into central and southwestern Nebraska, adjacent Colorado, and northeastern North Dakota. Meanwhile, D1A conditions were introduced for a small area in north-central North Dakota. Farther south, moderate rains also led to the removal of D0A conditions from part of northwestern Kansas.

The Upper Mississippi Valley and Great Lakes Region: Wet weather brought drought improvement to parts of northern Minnesota, the northern and eastern Upper Peninsula of Michigan, and a few sections of southern Minnesota; however, only scattered light to moderate precipitation fell elsewhere, allowing dryness to persist or locally intensify. Record daily rainfall totals late in the period led to weekly amounts of 4 to 8 inches for a small part of the western Minnesota Arrowhead, where conditions improved from D3AH to D1AH. Farther east, much of the D3AH in Michigan’s Upper Peninsula improved 1 category due to heavy rains in the last couple of weeks, but patches of D3AH persisted within a larger D2AH region stretching from west-central Minnesota northeastward through most of the Minnesota Arrowhead and the western half of the Upper Peninsula.

The Southeast: In the broad area of dryness that covered areas from the middle and lower Mississippi Valley eastward through the Ohio Valley, the Southeast, and the southern Atlantic states, hot weather and little or no rainfall allowed conditions to persist or worsen from the Florida Panhandle and Georgia northward through Alabama, eastern Tennessee, most of the Carolinas (except the small area in eastern North Carolina soaked by Tropical Storm Gabrielle), the southern Virginias, southeastern Kentucky, and the mid-Atlantic Coastal Plain. As a result, D4AH expanded into central and northeastern Georgia, the western Carolinas, northeastern Tennessee, and southeastern Kentucky while D1AH to D3AH areas broadened in adjacent areas, most notably southern Virginia and the Carolinas. Farther south, a dry start to September across interior southern Florida induced an eastward expansion of D0 to D2 conditions, with the D2 area stretched to include Lake Okeechobee, which is at exceptionally low levels for this time of year.

In sharp contrast, heavy to excessive rainfall brought substantial drought relief to much of Arkansas, the southern half of Missouri, parts of western Tennessee, and the northern Ohio Valley. Between 5 and 9 inches of rain drenched parts of the states adjacent to the Mississippi River, and fairly widespread 2 to 5 inch totals were observed in other parts of the aforementioned regions. These downpours led to broad reductions in assessed drought severity across central and northeastern Arkansas and much of southern Missouri, in several areas by more than 1 category. Farther north and east, the rains eroded the western extent of D3AH and D4AH conditions in central and western Tennessee, and led generally to 1-category reductions in central and southern sections of Ohio and Indiana, except immediately adjacent to the Ohio River, where lesser rainfall totals were reported.

The Northeast: One to locally four inches of precipitation reduced the southward extent of D0A and D1A conditions in western New York last week, and the northwestward extent of D0A conditions in western Massachusetts. Otherwise, light to moderate rainfall in other parts of last week’s dry areas kept conditions intact, with some expansion of D1A conditions in northern New York.

Alaska, Hawaii, and Puerto Rico: Increased rainfall during the past several weeks led to the elimination of D0 conditions in parts of interior southern Alaska. Meanwhile, light precipitation at best kept D0 to D2 conditions as they were last week across southeastern Puerto Rico and parts of Hawaii. The persistent dryness in eastern Oahu led to the introduction of mandatory irrigation water restrictions in the Waimanalo area.
Looking Ahead: Moderate to heavy rains may fall on some of the areas of dryness and drought affecting the Southeast during the next 5 days (through September 17), with amounts approaching or exceeding an inch forecast for a swath from eastern North Carolina southward and southwestward through much of South Carolina, Georgia, Florida, central and southern Alabama, and southern Mississippi. The remnants of Tropical Storm Humberto, making landfall just west of the Louisiana border in Texas late Wednesday, may fuel locally higher amounts in the states adjacent to the lower Mississippi River through the end of the workweek, and possibly farther east thereafter. In contrast, only isolated amounts exceeding 0.5 inch are forecast for the rest of the country’s dry areas. For the ensuing 5 days (September 18 – 22), the odds favor above-normal precipitation for the northern half of the Intermountain West and the Great Lakes region while drier-than-normal conditions are expected to return to the middle and lower Mississippi Valley, the southern Ohio Valley, the Deep South, the central and southern Appalachians, and much of the southern Atlantic states.

Author: Rich Tinker, Climate Prediction Center, NOAA

http://www.drought.unl.edu/dm/monitor.html