Nationwide
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In the form of shortwave troughs or closed lows, a couple of Pacific weather systems moved in the jet stream flow across the contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week. The weather systems brought rain or snow to the coastal Pacific Northwest, dried out as they traversed an upper-level ridge over the West, then picked up the Gulf of Mexico and Atlantic moisture as they moved across the southern Plains to East Coast.
With locally over 3 inches, an inch or more of precipitation fell over the coastal and Cascade ranges, with up to an inch over parts of the northern Rockies. Otherwise, most of the West was dry. Only a few areas in the Northwest and southern Rockies had more than a quarter-inch of precipitation.
Generally, the 1+ inch bands of precipitation were wetter than usual, while the areas with less than that were below average. Much of the northern Plains to Upper Mississippi Valley was dry. Improvement in drought conditions occurred where precipitation was above normal, while drought expanded or intensified in some areas where dryness continued.
Temperatures were near to cooler than usual across much of the West, Southern Plains, and Lower Mississippi Valley, and warmer than average in the northern Plains, South Texas, Great Lakes, Gulf Coast, and East Coast. Maps of 7-day, 14-day, and 28-day USGS streamflow measurements show below-normal streamflow from northern California, Nevada, and southern Idaho to the Four Corners states; and across southwest Nebraska to western Texas. They consistently show below-normal streamflow over central Texas, central Illinois to northern Indiana, and western Pennsylvania to western New York.
The satellite-based Vegetation Health Index shows stressed vegetation across the California valleys and southern California, the Southwest, parts of the central Plains and Ohio Valley, and especially in southeastern New Mexico to western Texas. Where VegDRI is still in season, it shows drought across the Southwest and West Texas and parts of the Northeast (Maine). QuickDRI is still in season, it indicates very dry conditions from southeastern Wyoming and western Nebraska, southward across Colorado, New Mexico, and western Kansas.
Evapotranspiration (EDDI) for the last week has been high in California and the Southwest to the southern Plains, in the northern Plains, and southern Alabama and Georgia. The EDDI shows high evapotranspiration across California and the Southwest, Great Plains, and Southeast to Northeast at the 2- to 3-week time scales, and across much of the West and Plains, Midwest, and Northeast at the 1- to 9-month time scales.
USGS real-time groundwater level data show low groundwater at points across the West, in northern Indiana, southern Georgia, and parts of the Northeast, and a couple of gauges in southern Alaska. NASA GRACE satellite-based groundwater estimates show low groundwater across most of the West to central and southern High Plains, most of New York to New England, much of Texas, and parts of North Dakota, Pennsylvania, Virginia, Alabama, Georgia, and Florida.
Soil moisture is dry across the West from California to the southern and central Rockies, in the southern and central High Plains (mostly southwest Nebraska and northwest Kansas), in North Dakota, across Nebraska and Iowa, across central Illinois to northern Indiana, parts of Pennsylvania and New York, and (for some indicators) most of New England. Snow telemetry (SNOTEL) is above average in Washington, Oregon, the Sierra Nevada, and parts of the other western states. It is still below normal across much of Utah and other parts of Idaho, Montana, Wyoming, Nevada, Colorado, and New Mexico. But this is early in the snow season and normal amounts are low.
The Standardized Precipitation Index (SPI) shows dry conditions in various places at different time scales. These include North Dakota to Wyoming, northeast Texas to the Tennessee Valley, and parts of the West (at the 1-month time scale); California to the central and southern Rockies, much of the Great Plains, northern Missouri to northern Indiana, and parts of the Northeast (2 to 4 months); California to the central and southern Rockies, much of the Great Plains, Iowa, northern Indiana to Ohio and Michigan, most of Northeast (6 to 12 months); parts of Pacific Northwest (9 to 12 months); and the Southwest to southern and central High Plains, and parts of Pacific Northwest, Texas, Iowa, Indiana, and the Northeast (24 months).
The West
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Even though over 2 inches of precipitation fell locally in the coastal Pacific Northwest, it was still below average. Only small parts of Montana, Arizona, and New Mexico were wetter than average this week.
The rest of the West had little to no precipitation, or what precipitation that fell was below normal. Abnormal dryness contracted in parts of Washington and northern Idaho where the indicators reflected improving conditions in recent weeks, and drought improved in a few parts of Oregon and worsened in other regions. Severe to exceptional drought expanded in Utah, with exceptional drought expanding in parts of Nevada, Arizona, and Colorado.
Extreme and exceptional drought expanded in parts of New Mexico. Portions of northeast Nevada received precipitation this USDM week, but it was still below average. The summer monsoon’s failure resulted in record dryness to the Southwest states, and record heat over warm-season increased evapotranspiration, resulting in record Standardized Precipitation Evapotranspiration Index (SPEI) values over the last 3 to 6 to 9 months.
The SPEI values were not the only record, they exceeded previous records by huge margins. The expansion of exceptional drought reflected this prolonged dryness. According to USDA reports, topsoil moisture was short to very short across 82 percent of New Mexico, 81 percent of Utah, 75 percent of California, 54 percent of Montana, 47 percent of Idaho, 42 percent of Oregon, and 35 percent of Nevada. In Oregon, 20 percent of the winter wheat crop is in poor to very poor condition. Jiggs Reservoir, in northeast Nevada, is nearly dry.
The High Plains
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Central and eastern parts of Kansas and strips in the northeast and southeast Nebraska received half an inch or more precipitation, with over 2 inches falling in northeast Kansas. Parts of Colorado also received above-normal precipitation. But the rest of the High Plains region was dry.
Moderate to severe drought shrank in southeast Nebraska and northeast Kansas, but moderate to severe drought expanded in parts of the states from North Dakota to Kansas. Extreme drought expanded slightly in southwest Kansas and was introduced in central North Dakota. Exceptional drought shrank slightly in central Colorado.
According to USDA reports, half to two-thirds of the topsoil moisture was short to very short in all of the High Plains states except Colorado, where 83 percent of the topsoil moisture was short to very short. USDA statistics show that 38 percent of the winter wheat was in poor to very poor condition in Colorado. In Nebraska and Kansas, the winter wheat statistics were 26 percent and 22 percent, respectively, poor to very poor. Nationwide, the U.S. winter wheat condition index was the lowest since 2012.
The South
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Western parts of Texas remained dry this week, while half an inch or more of rain fell across the rest of the region. Two inches or more fell across parts of southern Texas to Mississippi. Abnormal dryness to exceptional drought contracted in southern Texas, abnormal dryness shrank in Louisiana and Mississippi, and moderate drought was reduced in Arkansas. But moderate to extreme drought expanded in other parts of Texas, which were drier than average for the week, and exceptional drought grew in west Texas.
Abnormal dryness and moderate drought expanded in northern Mississippi and western Tennessee, where this week’s rainfall was below normal. According to USDA reports, topsoil moisture was short or very short across 61 percent of Texas, 43 percent of Oklahoma, and 20 percent of Mississippi; 34 percent of the winter wheat was in poor to very poor condition across Texas. —UNL Drought Monitor
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