Latest drought monitor over Iowa


Monthly drought outlook


Map of below normal 7-day average streamflow compared to historical streamflow for the day of the year (Iowa)


Amount of precipitation needed to end drought


Drought severity index by division


4 month precipitation departures


Week Date None Abnormally Dry Moderate Severe Extreme Exceptional DSCI
Current 2020-12-01 38.07 61.93 36.35 17.59 4.03 0.00 120
Last Week 2020-11-24 31.88 68.12 36.35 17.59 4.03 0.00 126
Three Months Ago 2020-09-01 0.63 99.37 82.77 37.25 14.65 0.00 234
Start of Calendar Year 2019-12-31 100.00 0.00 0.00 0.00 0.00 0.00 0
Start of Water Year 2020-09-29 30.57 69.43 46.89 22.57 0.00 0.00 139
One Year Ago 2019-12-03 100.00 0.00 0.00 0.00 0.00 0.00 0


A couple Pacific weather systems, in the form of shortwave troughs or closed lows, 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 Gulf of Mexico and Atlantic moisture as they moved across the southern Plains to East Coast. An inch or more, with locally over 3 inches, 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. East of the Rockies, bands of an inch or more of precipitation, with locally 2 inches or more, fell across Kansas to the Great Lakes and along the Ohio River to northeast Ohio. Widespread 2+ inches of rain fell from coastal Texas to the Carolinas, and from Virginia to New England. A large shield of half an inch or more of precipitation surrounded these bands and extended from the southern and central Plains to the East Coast, and from the southern Great Lakes to Gulf of Mexico Coast. Generally the 1+ inch bands of precipitation were wetter than normal, while the areas with less than that were below normal. 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 normal across much of the West, southern Plains, and Lower Mississippi Valley, and warmer than normal 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 are consistent in showing 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). Where QuickDRI is still in season, it shows very dry conditions from southeastern Wyoming and western Nebraska, southward across Colorado, New Mexico, and western Kansas. The KBDI shows significantly dry conditions in California, Nevada, Utah, Arizona, New Mexico, and Texas, and a few spots in eastern Wyoming, western Nebraska, northern Florida, southern Alabama, and southern Georgia. NIFC maps show large wildfires still burning in California, and several in Oklahoma, central Appalachians, and a few elsewhere. Evapotranspiration (EDDI) for the last week has been high in California and the Southwest to the southern Plains, in the northern Plains, and in 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 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 (especially 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 (CPC, NLDAS, UCLA/VIC models; satellite-based AAFC/SMOS, GRACE, NASA/SPoRT analyses). SNOTEL snowpack (SWE percentiles) is above normal in Washington, Oregon, the Sierra Nevada, and parts of the other western states, but it is 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). When the desiccating effects of hot temperatures are included, the Standardized Precipitation Evapotranspiration Index (SPEI) shows more intense drought conditions over the SPI dry areas than indicated by the SPI.


The jet stream will continue to be active during the next couple weeks, sending a parade of Pacific weather systems into the CONUS, while an upper-level ridge continues to hold sway over the West. For December 3-7, the coastal portions of the Pacific Northwest will receive precipitation, although not as much as this past week with generally less than an inch predicted by the models. The forecast has about an inch of precipitation falling along the Kansas-Oklahoma border, over parts of east Texas, from southern Louisiana to the Mid-Atlantic coast, and across New England. Two inches or more are progged from Delaware to southern New England. An envelope of an inch or less of precipitation should surround these wetter areas, from the western Great Lakes to the Atlantic Coast, and from the Ohio Valley to Gulf Coast. Most of the West, Texas, central to northern Great Plains, and Midwest have little to no precipitation expected. Temperatures are predicted to be warmer than normal from the central and northern Plains to East Coast, and below normal over the interior West. The outlook for December 8-12 is mostly dry. Odds favor below-normal precipitation across most of the CONUS, with only a strip from the Rockies to northern and central High Plains, as well as Alaska, having odds favoring wetter-than-normal conditions. Odds favor warmer-than-normal temperatures across most of the West, Plains, Midwest, and Northeast, with below-normal temperatures likely across parts of the Southeast and central Alaska.


Abnormal dryness and moderate drought contracted in southern parts of the Midwest which received beneficial above-normal precipitation, especially in Illinois and Indiana. But in northern parts, where the week continued dry, abnormal dryness and moderate drought expanded, especially in Minnesota. USDA statistics show that 40% of the topsoil moisture was short or very short in Iowa.