#Drought news: Worsening SPI and SPEI indicators led to expansion of D3 in N.E. and S.E. #Colorado and S.W. #KS, D0-D2 in E. portions of Colorado and W. portions of Kansas

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor.

Click here to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

A couple Pacific weather systems moved across the contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week. The storm track kept to the northern states, but the systems dragged cold fronts with them that stretched the width of the CONUS, from the Great Lakes to the Gulf of Mexico coast. The systems spread rain and snow to the coastal Pacific Northwest and parts of the northern Rockies, but they weakened as they moved through a western ridge. This circulation pattern starved them of moisture, so much of the West to Great Plains received little to no precipitation, but the fronts picked up Gulf of Mexico moisture as they moved east, spreading precipitation across the Lower Mississippi to Ohio Valleys, eastern Great Lakes, and Northeast. Only a few areas received above-normal precipitation for this time of year, including spots in the Pacific Northwest, Ohio Valley, Deep South Texas, and the southern half of Florida. Weekly temperatures averaged near to cooler than normal in the Pacific Northwest, Great Lakes, Ohio Valley, and Mid-Atlantic states. Much of the West, Great Plains, and Southeast were warmer than normal. Persistent above-normal temperatures in the Plains contributed to excessive evapotranspiration in western portions of the Great Plains as well as parts of the West, as seen in EDDI and ESI indicators. Lack of precipitation, excessive evapotranspiration, and windy conditions further dried soils, again especially in western portions of the Plains, as seen in several soil moisture indicators. Drought indicators such as the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) showed dry conditions at long-term time scales in the West to northern Plains, at short-term time scales in the Southeast to Mid-Atlantic and Lower Mississippi Valley regions, and both short- and long-term time scales from the Southwest to southern and central Plains. Precipitation over the last 4 weeks lessened drought intensity slightly in parts of the West, but continued dryness expanded or intensified drought in parts of the Plains, Deep South, Southeast, and Mid-Atlantic states…

High Plains

Except for half an inch or more of precipitation over the mountains of northern Colorado and northwest Wyoming, a tenth of an inch to no precipitation was observed across the High Plains region. Drying soils, high evapotranspiration, and worsening SPI and SPEI drought indicators led to expansion of D3 in northeast and southeast Colorado and southwest Kansas, and D0-D2 in eastern portions of Colorado and western portions of Kansas. Decreasing soil moisture, lack of snow, and dry long-term SPI/SPEI indicators prompted expansion of D3 in north central Wyoming and D1 and D2 in southeast Wyoming…

Colorado Drought Monitor one week change map ending November 23, 2021.

West

Half an inch to locally 2 inches of precipitation fell along coastal areas of Oregon and Washington, with half an inch over eastern Washington to northern Idaho. Less than half an inch occurred further south to northern portions of California and the Great Basin. Areas further south received no precipitation this week. Dry soils, high evapotranspiration, and severely dry SPI and SPEI values prompted expansion of D4 in northern Montana. According to November 21st statistics from the U.S. Department of Agriculture, 99% of Montana’s topsoil moisture was short or very short (dry to very dry) and 42% of the winter wheat crop and 99% of the pasture and rangeland were in poor to very poor condition. D1-D3 expanded in eastern New Mexico. Even though California and Nevada were mostly dry this week, the impacts from the atmospheric river event and frontal rains of October continued to be felt. With moist soils, wet SPI and SPEI indicators for the last 1 to 6 months, and slightly improved reservoir levels and snowpack, a reassessment of conditions resulted in the pullback of D4 in the Sacramento River Valley in California, and a pullback of D2 and D3 in northern Nevada. D3 was also pulled back slightly in southwest Montana and adjacent Idaho…

South

Half an inch to locally an inch of rain fell over Mississippi, Tennessee, eastern parts of Arkansas, and parts of Louisiana. Half an inch to locally over 2 inches was observed over Deep South Texas. Other than those areas, most of the South received no precipitation this week. Drying soils, high evapotranspiration, and worsening SPI and SPEI drought indicators prompted expansion of D0-D3 in western parts of Oklahoma and Texas, while D0-D1 expanded in eastern portions of Texas and Oklahoma to western parts of Mississippi. The rains in Deep South Texas eliminated moderate drought and contracted abnormal dryness along the southern Rio Grande River…

Looking Ahead

A frontal system will sweep across the eastern CONUS during November 24-30 with another Pacific weather system moving into the Pacific Northwest near the end of the period. They will be moving through a circulation pattern consisting mainly of an upper-level ridge in the West and trough in the East. An inch to 2 inches of precipitation is forecast to fall along the Texas coast to east Texas and over northern portions of the Northeast, with half an inch or more stretching from the southern Rio Grande Valley to New England. Half an inch to an inch of precipitation is expected over the northern Rockies and coastal sections of Oregon and Washington, with up to 5 inches in the forecast for northwest portions of Washington. Up to half an inch is predicted for parts of the Four Corners states in the Southwest, parts of the Great Lakes, and coastal parts of the Mid-Atlantic to Northeast states. Little to no precipitation is expected for much of the West, Great Plains, and Upper Mississippi Valley due to the circulation pattern associated with the western ridge. With the storm track to the north and systems moving into the Great Lakes, much of the Southeast will receive little to no rainfall. Temperatures are expected to be warmer than normal in the western and central CONUS and cooler than normal along the East Coast. The outlook for December 1-6 shows drier-than-normal weather favored from the Southwest to Great Lakes, from the Ohio Valley to Southeast, and western half of Alaska, with wetter-than-normal weather favored over the Pacific Northwest to northern Rockies, parts of southern Texas, and southeast Alaska. Odds favor colder-than-normal weather over the East Coast and warmer-than-normal weather over the western and central CONUS, with the warmer-than-normal conditions shifting eastward as the period progresses. Colder-than-normal temperatures dominate Alaska in the outlook.

US Drought Monitor one week change map ending November 23, 2021.

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