Heat continues to be the story for much of the Plains

Rainfall was highly variable across the nation this past week. Totals exceeding 2 inches were widespread from northern and eastern Indiana through much of Ohio and into West Virginia and western Pennsylvania.

Interior sections of central and northern Missouri saw widespread totals topping 2 inches, with a few isolated patches receiving 4 to 5 inches. Other areas with more scattered totals more than 2 inches included the Upper Midwest and east-central Great Plains. More moderate amounts, with isolated spots recording 2 to 3 inches, were dotted across the Desert Southwest where a decent monsoonal circulation remained in place. Meanwhile, little or no precipitation fell on most locations in the seasonably-dry Far West, the Great Basin, the Intermountain West, much of the central and northern Rockies, and most of the Plains.

Temperatures averaged at least slightly above normal from the Great Basin and Southwest through the southern Plains and most of the Lower Mississippi Valley. Numerous locations from near the Great Basin through Oklahoma and western Texas average 6 to 10 degrees Fahrenheit above normal. Meanwhile, subnormal temperatures dominated the northern Plains. Other sites across the Lower-48 recorded near-normal temperatures for the week.

The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the U.S. Department of Agriculture and the National Oceanic Atmospheric Administration. (Map courtesy of NDMC.)

South

Dryness and drought have been expanding and worsening over much of the South Region for the past few weeks.

Rapidly deteriorating conditions have been observed across Oklahoma, the Texas Panhandle, and adjacent areas of Arkansas, but almost all states saw declining conditions this past week. Farther west, deterioration was introduced through most of Oklahoma (especially the eastern half of the state), the Red River Valley, much of the Texas Panhandle and northeastern Texas, and western Arkansas.

Oklahoma has seen very little precipitation over the last 30 days, with most locations reporting less than 25% of the normal. Temperatures averaging 3 to 7 degrees above normal mid-summer values significantly exacerbated the drying conditions across much of Oklahoma and northern Texas, including the Panhandle. Temperatures averaged near or up to 3 degrees above normal elsewhere. Much more abundant rainfall prior to the past 30 days is keeping longer-responding impacts from ramping up too quickly, but some crops and streamflows are being deleteriously affected.

Almost half of Texas oats and over one-third of Oklahoma soybeans are in poor or very poor condition. Across Oklahoma, 44% of pastures and rangelands are in poor or very poor condition, as are 33% of those in Arkansas.

Midwest

A variable precipitation pattern was observed across the Midwest Region, with deficient precipitation persisting across much of the northern tier of the region, along with scattered locations from central Illinois into southern Indiana.

Meanwhile, a swath of heavier amounts brought improvement to significant locations across south-central and northern Missouri, central and eastern Iowa, and the southern tier of the Great Lakes region. Over the past 30 days, most areas in a band from north-central Minnesota through northern Wisconsin recorded less than 25% of normal precipitation, with many locations reporting several tenths of an inch at best during that period.

Amounts have been a little more generous across the southern and northern reaches of Missouri, western Iowa, and central through southwestern Minnesota, but many sites here reported half of normal or less during the past 30 days. In contrast, 30-day totals have been well above normal in part of northern Minnesota, south-central Minnesota through eastern Iowa, part of southern Iowa, and central Missouri. This has resulted in the patchwork of varying severities of dryness through the Region, but severe drought is most common through a large part of central and northern Minnesota, and smaller sections of southwestern Minnesota and interior west-central Iowa.

High Plains

Moderate to heavy rainfall doused portions of eastern Kansas and adjacent Nebraska, leading to some limited relief, but totals were considerably lower elsewhere.

Over 0.5 inch with isolated heavy amounts were observed in southern North Dakota, western and southern South Dakota, numerous patches across Nebraska, south-central and west-central Kansas, and the higher elevations of Colorado.

Other locations measured a few tenths of an inch, if any. Improvements were restricted to small sections of north-central and southeastern Nebraska while dryness and drought persisted or intensified elsewhere. Areas from south-central through northeastern Colorado, southernmost and northwestern through north-central Kansas, northeastern Nebraska, and the northern half of the Dakotas saw the most widespread deteriorations.

Over the past 30 days, most locations outside the highest elevations of Wyoming and Colorado have recorded well below normal precipitation, with less than 25% of normal amounts recorded over central and southwestern Kansas and much of North Dakota. There are a few stripes in the Great Plains with near or above-normal 30-day totals, but these conditions cover much smaller areas than those experiencing dryness and drought.

Currently, large sections of Colorado and Wyoming are enduring severe to exceptional drought, with the worst conditions affecting significant portions of Colorado and a few patches in western Nebraska. In the Great Plains, severe or extreme drought also extends across much of Nebraska and some adjacent locales, the central and western Dakotas, and a few patches in southeastern South Dakota and southwestern Kansas.

The dryness is impacting especially surface moisture stores, including areas of reduced streamflows and degraded crops. Not all crop damage may be the result of dryness and drought, but it is the most significant contributing factor. In Colorado, 64% of pastures and rangelands are in poor or very poor condition (5-year average 23% ), along with 70% of those in Nebraska (5-year average 30%), and 75% in Wyoming (5-year average 38%).

Several crops in Colorado have a significant proportion in poor or very poor condition, including 46 percent of corn (5-year average 15%) and 57% of sorghum (5-year average 8%). In North Dakota, 53% of sorghum and 40 % of corn are in similar condition (5-year averages of 13 to 15%, respectively). Significantly above-normal temperatures have also prevailed during the last 30 days, with temperatures averaging generally 6 to 9 degrees above normal in the western Dakotas, the adjacent High Plains, central and western Colorado, and western Wyoming, with the largest departures observed in the latter region.

West

Moderate to locally heavy precipitation (0.5 to 3 inches) fell on much of Arizona and New Mexico primarily due to monsoonal convection. Farther north, a few tenths of an inch with isolated higher amounts of over an inch were recorded across Utah, much of the Great Basin, and some adjacent areas.

The rest of the West Region was dry, with only isolated locations reporting as much as 0.2 inch. These conditions brought little change to dryness and drought across the West Region, with changes restricted to several areas of deterioration across the plains of Montana and part of the adjacent northern Rockies, similar to conditions farther east across the northern tier of the central Lower-48.

Dryness and drought continue to cover a large proportion of the West Region, sparing only parts west-central Montana. Conditions have been exacerbated by 30-day temperatures averaging 4 to 8 degrees above normal across much of southern Montana, and scattered locations across the Southwest.

One-half to three-quarters of rangelands in New Mexico are in poor or very poor condition, which is well above average for this time of year. In addition, multiple years of persistently below-normal precipitation has left some large reservoirs in the West with extremely low water stores.

The contents of Lake Mead have dropped to an all-time low since daily reports are available, back to 1937. By Aug. 10, the amount of stored water dropped below 7 million acre-feet (capacity is more than 28 million acre-feet).

Looking ahead

During Aug. 13 to 17, moderate to heavy rain (over an inch) is forecast across the central and northern High Plains, the northern Rockies, the Colorado Rockies, and scattered locations over the central and western Four Corners region.

Also rainfall is predicted for much of the northern and central Great Plains. The highest totals (3 inches or more) are expected across part of east-central Montana, the northeastern quarter of Colorado, and much of a band from central Iowa into western Indiana.

In contrast, light precipitation at best is anticipated across the central and southern Plains and the central to southern Rockies. Meanwhile, areas from the south-central Great Plains across the Southeast are expected to record daily highs averaging 5 to 11 degrees above normal, with the largest anomalies expected from Arkansas through central Tennessee. Daily highs should average 3 to 6 degrees below normal over much of the northern Intermountain West, and northern reaches of the Rockies and Plains. Other locations should average closer to normal.

The 6- to 10-day outlook (Aug. 18 to 23) at least marginally favors above-normal precipitation across the northern halves of the Mississippi Valley and Plains, and from the Rockies to the West Coast. Subnormal totals are somewhat favored in the southern Great Plains. Meanwhile, warmer than typical mid-August conditions should dominate all 50 states.

Richard Tinker is with NOAA/NWS/NCEP/CPC.