An upper-level ridge dominated the central contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week (September 14-20).
It was bracketed by an upper-level trough that moved out of the Northeast early in the week and a Pacific upper-level trough which moved into the West as the week progressed. Pacific weather systems moved across the northern states between the troughs. This pattern resulted in above-normal precipitation across much of the West and parts of the Northeast. Fronts associated with the Pacific systems triggered showers and thunderstorms across parts of the central and northern Plains to the Mid- and Upper Mississippi Valley.
For the rest of the CONUS, a large dry air mass covered much of the southern Plains and East throughout the week. Rain occurred along a stationary front draped across Florida that was associated with the southern edge of the air mass. Still, it was a dry week for much of the South, Southeast, Mid-Atlantic, and Midwest regions. Temperatures averaged warmer than normal across the Plains to the Great Lakes and cooler than average across much of the West, Southeast, and northern New England.
Drought or abnormal dryness contracted where it rained, especially in parts of Florida, New Mexico, and the Northeast, in a swath from Iowa to Illinois.
Pacific weather systems dropped locally two or more inches of rain across parts of central and northern California and over local areas of the Great Basin and southern New Mexico. Half an inch or more of precipitation occurred over large parts of the interior West.
Other parts were dry this week, especially much of Washington, Oregon, northern Idaho to northwestern Montana, and southern California to parts of New Mexico. Groundwater continues low, and many reservoirs were still very low to a near-record low. The water levels in most reservoirs in New Mexico are well below average. The August 2022 total combined end-of-month storage of 12 large reservoirs in the state ranked among the three smallest August totals since 1990.
The precipitation that fell this week did little to make up deficits built up over the last 5 years, so little improvement was made on this week’s map over the areas that received precipitation. One exception was southern New Mexico and adjacent Arizona, where D1-D3 contracted in the wetter areas this week that has also benefited from a wet monsoon season.
In northern parts of the West region, D0 was added to western Washington and northwest Oregon, where streams were low, very warm temperatures increased evapotranspiration and continued to dry soils, and precipitation was below average for the last 3 months. D1 expanded in northern Idaho, where several indicators reflected the dry conditions of the previous 3 months, and several dozen large wildfires continued to blaze.
According to USDA statistics, all of the states in the region except California, Nevada, and Arizona had half or more of their topsoil moisture short or very short of moisture.
The High Plains
Parts of the High Plains region had rain while other parts were dry. Up to two inches fell locally in parts of several states.
Especially dry areas occurred in parts of the Dakotas, Montana, Kansas, and Colorado. The lack of rain was accompanied by unusually hot temperatures regionwide, which increased evapotranspiration and accelerated the drying of soils. The drying soils and dry ponds and waterholes led to extensive expansion of D0-D2 in North Dakota and Montana and D0-D4 in South Dakota and Kansas. Groundwater levels are low, with wells in Wichita, Kansas, going dry. According to media reports, a water emergency developed in Caney, a town in southeast Kansas, when the water stopped flowing over the Little Caney River’s dam; there are 6 weeks of water supply left.
D1 and D2 expanded in parts of Colorado, and D3 expanded in southeast Wyoming, while other parts of the state saw a contraction of D0 and D1. Nebraska also had some contraction of D2 but an expansion of D1-D3 in other parts of the state. According to USDA statistics, all states in the region had half or more of the topsoil moisture short or very short moisture.
In Nebraska and Kansas, three-fourths of the pasture and rangeland was in poor to very poor condition, while the value was 50% for Colorado, 55% for South Dakota, and 58% for Montana.
A few areas of the Gulf Coast and western Texas received up to half an inch of rain this week, but the South region was, for the most part, dry with no rain falling.
Moderate and severe drought contracted slightly in southern Texas, abnormal dryness and moderate drought expanded in a couple of other areas of the Lone Star State, and abnormal dryness expanded in Tennessee. The biggest changes occurred in Oklahoma and Arkansas. D1-D4 expanded in Oklahoma and D0-D2 expanded in Arkansas. Soils continue to dry, and groundwater and stream levels are low.
According to U.S. Department of Agriculture (USDA) statistics, 82% of Oklahoma’s topsoil moisture is short to very short of moisture (dry to very dry). The only drier years in mid-September in data going back to 2010 were 2011 and 2012, which were very bad drought years. All states in the region except Louisiana and Mississippi had half or more of the topsoil moisture short or very short of moisture. Almost 70% of the pasture and rangeland in Oklahoma was in poor to very poor condition. Ponds in Oklahoma are drying up and 63% of the cotton crop is in poor to very poor condition. — UNL Drought Monitor