Heat remains the story for the Plains

Most of the nation endured a hot and drier-than-normal week, including most areas which are are in drought conditions, according to the latest U.S. Drought Monitor.

Temperatures averaged 5 to 10 degrees Fahrenheit higher and accompanied deficient precipitation over a large area from the Rockies to the Appalachians and central Gulf Coast region, prompting drought intensification over large parts of the upper Mississippi Valley, the central states, and the southern tier of the country west of the Florida Panhandle.

Improvement was limited to the band of heavy precipitation from Hurricane Idalia, and in scattered locales affected by the tropical moisture surge in the Desert Southwest, from southeastern Utah to central Arizona westward toward central California.

According to the U.S. Department of Agriculture, the coverage of topsoils short or very short of moisture increased by 6% this past week, now covering 58% of the contiguous 48 states. This is the greatest coverage at this time of year in more than nine years, the prior record in that short interim being just over 50% in 2020.

A surge of tropical moisture pushed northward into the southwestern U.S., continuing northward across the Great Basin, Intermountain West, and adjacent Rockies into adjacent Canada. Heavy rainfall fell in a broken pattern over this general area, with the highest amounts reported across interior southeastern California, over much of the middle Colorado River Basin, and across scattered areas farther north.

The heaviest amounts outside the lower Colorado River Basin fell on higher elevations and over areas where precipitation was enhanced by orography, as is typical.

South

Brutally hot and dry weather again this week kept dryness entrenched across Texas, southern Oklahoma, Louisiana, and southern Mississippi. For the past two months, temperatures averaged 4 to 8 degrees above normal from most of the Four Corners states eastward through most of Texas and Louisiana, and across southern Mississippi.

A solid swath of extreme to exceptional drought (D3-D4) is now entrenched from central Texas eastward through most of Louisiana and southern Mississippi, expanding slightly northward as well.

Outside the large area of solid D3-D4 conditions, conditions generally deteriorated where dryness was antecedent or on the cusp of developing and remained essentially unchanged elsewhere. In contrast, Tennessee and most of Arkansas remained free of any systemic dryness.

According to the USDA, the cotton crop has not fared well this summer, suffering through the persistent hot and rain-free weather.

Almost 80% of the Oklahoma cotton crop is in poor or very poor condition, as is 61% of Texas cotton. Peanuts, sorghum, soybeans, and rice planted in Texas, Louisiana, southern Oklahoma, and southern Mississippi were also being stressed by from heat and lack of rainfall, although the proportion in poor condition or worse is considerably lower.

In addition, deteriorating pastures and rangelands are stressing livestock. As of early September, 72% of Texas rangelands, 63% of Louisiana pastures, and almost 40% of Mississippi pastures were in poor or very poor condition.

Midwest

Excessively hot and dry weather dominated this region last week, worsening an already-serious drought in the western half of this region. D2 and D3 conditions expanded markedly across Wisconsin, Minnesota, Iowa, and Missouri under conditions highly favorable for the rapid intensification of drought.

The moisture budget over the eastern half of the region is in far better shape, but areas of abnormal dryness expanded somewhat, and isolated small pockets of moderate drought began to emerge by the end of the week. Agriculture and surface moisture has been stressed by the drought. In Missouri, 40% of the corn crop and 23% of soybeans were in poor or very poor condition.

Nearly two-thirds of pasture and rangeland in Minnesota was in poor or very poor condition, as were 46% of Iowa pastures and 43% of Missouri pastureland.

High Plains

Conditions vary markedly from southeast to northwest here. Similar to western sections of the Midwest Region, Kansas and Nebraska in the southeastern High Plains region are largely covered by drought, including significant expanses of D2 to D3 conditions, with new or expanded D4 (exceptional drought) noted in a few locations. Farther west and north, conditions are much more favorable.

To the north and west of central Nebraska, dryness and drought are restricted to the eastern and northern Dakotas, and southwestern Colorado. As in other parts of the nation’s midsection, agricultural drought stress is palpable, and on the rise.

Across Kansas, 40% of soybeans are in poor or very poor condition, as are 33% of the corn crop, 29% of sorghum, and 47% of rangelands.

Across Nebraska, about one quarter of all the aforementioned crops are in poor or very poor condition. This region did not see the degree of deterioration observed in the Midwest region, with significant worsening most notable in central and eastern Kansas.

West

Monsoon rains remained subpar across eastern Arizona, New Mexico, and southwestern Colorado, prompting a continued slow deterioration in dryness and drought there. With the monsoonal wet season winding down during September, the odds for heavy precipitation episodes declines, and thus the prospects for significant relief from the intensifying dryness and drought become progressively worse.

Dryness and drought also cover large parts of Washington and Oregon as well as the northern tiers of Idaho and Montana. Some deterioration was noted in north-central Montana, but farther west, conditions were essentially unchanged in northern Idaho and the Pacific Northwest.

Looking ahead

According to the Weather Prediction Center, Sept. 7 to 11  will bring some much-needed rainfall to the parched central Plains. Over 0.5 inch is forecast from parts of Oklahoma and the Texas Panhandle northward through Nebraska, with 1.5 to locally 3 inches anticipated in parts of central Kansas.

A broad area covering most of the Plains and the lower Mississippi Valley are expecting several tenths of an inch of precipitation. Most other places might see light precipitation, but little or none is expected across the far West, most of the Rockies, southern Texas, the southern High Plains, the middle Mississippi and lower Ohio Valleys, And parts of the interior Deep South.

Hot weather is expected to accompany subnormal rainfall totals along the southern tier of the country from southernmost California eastward through the central Gulf Coast region, as has been the case much of the summer. Daily maximum temperatures are expected to average 5 to 9 degrees above normal there.

In contrast, milder than normal temperatures are expected to displace the heat that has recently affected parts of the nation’s midsection, with readings expected to average 3 to 7 degrees below normal across much of the region from the central High Plains eastward across the middle Mississippi and Ohio valleys.

The Climate Prediction Center’s six- to 10-day outlook, valid, Sept. 12 to 16, favors a similar pattern. Odds favor above-normal temperatures from the South Atlantic Region westward across the southern tier of the contiguous 48 states, over most areas from the Rockies westward, and the northern Plains.

Meanwhile, below-normal temperatures are favored across a large swath from the south-central Plains eastward through most of the Mississippi Valley, the upper Southeast, the Appalachians, the Atlantic Piedmont, the Mid-Atlantic, and the lower Northeast.

There are enhanced chances for surplus precipitation across the central and southern Rockies, much of the central and southern Plains, the southern half of the Mississippi Valley, the Ohio Valley, the interior Southeast, the Appalachians, the mid-Atlantic, and the Northeast. In contrast, drier-than-normal weather is favored across most of the Great Lakes, the northern tiers of the Plains and Rockies, the northern Intermountain West, and the Pacific Northwest, as well as across the Florida Peninsula.

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