Click here to go to the US Drought Monitor website. Here’s an excerpt:
Summary
A strong upper-level low pressure system funneled Gulf of Mexico moisture into the central U.S. at the beginning of this USDM week, triggering widespread heavy rains and severe weather. Two to 5 inches of rain fell on November 17 from eastern Texas to Missouri eastward to Mississippi and Illinois. An inch or more of precipitation was observed from northwest Kansas to central Nebraska, across Iowa and Minnesota, and into the western Great Lakes. As the Low and cold front moved eastward on the next day, 1 to locally 3+ inches of precipitation fell across the Southeast, Tennessee Valley, and Upper Mississippi Valley. By the third day, the system had dropped an inch or more of precipitation along the East Coast. Meanwhile, another storm system brought rain and snow to the Pacific Northwest, with 1 to 3+ inches, and locally up to 5 inches, of precipitation measured in Washington and northwest Oregon west of the Cascades. Another system moved from the Pacific Northwest, across the Plains to the southern Great Lakes, leaving a blanket of snow in its wake, up to a foot or more deep in places. As a result, drought and abnormal dryness contracted over large parts of the country. The weather systems missed the Southwest and northern Plains. Virtually no precipitation fell across California to parts of Colorado, New Mexico, and Texas, with a tenth of an inch or less widespread across the northern Plains. Temperatures averaged warmer than normal across much of the East to northern Plains, and in parts of the central Plains and Far West. Cooler-than-normal temperatures dominated from the Pacific Northwest and Northern Rockies to the southern Plains…
California and Great Basin
Parts of the northern coast of California received up to 2 inches of precipitation this week, and some northern sections of the Great Basin measured a few tenths of an inch, but most of California and the Great Basin received no precipitation. According to November 22 USDA reports, 85% of the topsoil and 85% of the subsoil in California was rated short or very short of moisture (dry to very dry). In Utah, 48% of the subsoil and 36% of the topsoil was short or very short of moisture. No change was made to the drought depiction in this region…
Great Plains to Mississippi Valley
This week saw a continuation of widespread heavy rains across much of the eastern Great Plains and Mississippi Valley. An inch or more of rain fell from the eastern portions of the Plains states – from Texas to the Dakotas – eastward to the Mississippi Valley and beyond. A band of 1-inch precipitation stretched from northwest Kansas into central Nebraska. Two inches to locally 5+ inches was observed from eastern Texas and Oklahoma to Mississippi, western Tennessee, and Illinois. Two-plus inches of precipitation were measured across parts of South Dakota, Iowa, and Minnesota. This heavy precipitation effectively erased the D0 and D1 that remained from last week’s rains across southern and eastern portions of the region. D0 was removed from eastern Texas and southeastern Oklahoma. The rain in southeast Oklahoma contributed to Broken Bow and Hugo Lakes returning to near- to above-normal pool stage. D0-D1 disappeared from Arkansas and Mississippi, with only a small sliver of D0 remaining in northeast Mississippi to reflect longer-term precipitation deficits. D0 was removed from Missouri, southeast Iowa, southwest Tennessee, most of Illinois, and the confluence of the Ohio and Mississippi Rivers area. The recent rains in Illinois have restored soil moisture and benefited winter wheat. D1 was removed and D0 shrunk in Minnesota and Iowa. Heavy snow sliced away at the D0 in northwest Kansas, southwest Nebraska, and northeast Colorado. At the other end of the state, precipitation eroded D0 and deleted D1 in southeast Nebraska and northeast Kansas.
In the northern Plains where precipitation was sparse this week, D0 expanded in southwest North Dakota and adjacent South Dakota. Below-normal precipitation for the last 7-90 days, coupled with windy and warmer-than-normal weather in recent weeks, continued to dry soils, with 23% of the topsoil and 28% of the subsoil moisture short or very short in North Dakota. In Wyoming, the storm system that blew through this week increased snow depth 4-12 inches at SNOTEL stations in the Big Horns. But even with this increase, snow depth was still less than a foot in this region, and snow water content and water year-to-date precipitation still ranked in the lowest 20th percentile to driest fifth percentile, so no change was made to the D0 in northeast Wyoming. November 22 USDA reports rated 44% of the topsoil and 46% of the subsoil in Wyoming short or very short of moisture. With low streamflows and precipitation deficits stretching over the last 2-12 months and longer, the drought impacts designator for the D0 and D1 in Kansas and north central Oklahoma was changed to SL to indicate both short- and long-term drought conditions…
Pacific Northwest and Northern Rockies
Another round of precipitation in coastal Washington and northwest Oregon resulted in improvement to the drought depiction. Two to 5 inches, and locally more, this week added to the precipitation of last week to bring two-week totals to 15-20 inches, or more, in favored upslope areas. Streams were bank full and flooding in many areas west of the Cascade ridge line, especially in Washington. It should be noted that instantaneous streamflow observations are an important flash flood monitoring indicator, but they should never be used for drought monitoring; the base streamflow is best used for drought monitoring, and that is estimated by averaging over several days. The persistent heavy rains and swollen rivers in Washington improved reservoir levels. Seattle-Everett-Tacoma deactivated their water shortage response plans November 23 due to improving reservoirs.
Precipitation along and west of the Cascade Mountains was above normal for the last 7 to 90 days, and in some places above normal out to the last 12 months. The precipitation resulted in pullback of the D0 to the Cascade ridge line in Washington and contraction of D1-D3 in areas further north, and pullback of D0-D2 in northwest Oregon. But the weather systems producing this precipitation were embedded in a westerly flow, and areas in the rainshadow east of the Cascades continued to have below-normal precipitation at all time scales from the last 7 days to the last 36 months, so D2-D3 continued for Washington and Oregon east of the Cascades. The USGS 7-day, 14-day, and 28-day streamflow indicators show low streamflow in eastern Washington. According to the Bureau of Reclamation, November 22 reservoir statistics still showed low reservoir levels in the Yakima River Basin east of the Cascades, including Kachess and Cle Elum at 33% full each and Rimrock at 29% full. Kachess and Rimrock were well below average, even after the November precipitation. NRCS reservoir statistics are available on a monthly basis. The NRCS October 31 values for reservoirs east of the Cascade ridge line ranged from 30 to 70 percent of average and included 32% at Cle Elum Reservoir, 39% at Keechelus, 56% at Lake Shannon, 71% at Ross, 77% at Kachess, and 79% at Upper Baker.
Winter mountain snowpack is crucial to spring and summer water supplies. The Pacific Northwest experienced an abysmally low snowpack during the 2014-2015 snow season. The 2015-2016 snow season has started out with snowpack below average. In Washington, a handful of SNOTEL stations have 3 to 5 feet of snow in the northern Cascades, but most of the SNOTEL stations in the Cascades of Washington and Oregon had less than a foot of snow, even after the recent storm systems, and these are all at high elevations. This is still early in the snow season, but these values are less than 75% of normal, and in many cases less than 50% of normal. Snow depths ranged up to 2 feet in some of the higher SNOTEL stations in the northern Rockies of Idaho, but even many of these were still below normal for this time of year.
November 22 USDA reports noted that 18% of the winter wheat in Washington and 15 % in Oregon was rated in poor to very poor condition. In Washington, 38% of the winter wheat was rated in good to excellent condition, but this value dropped 3 percentage points compared to last week. More than half of the topsoil was rated short to very short of moisture in Oregon (55%) and Washington (51%), with 21% so rated in Idaho. Subsoil moisture conditions were even drier, with 76% short to very short in Oregon, 59% in Washington, and 38% in Idaho…
Southwest
Half an inch to an inch of precipitation fell across eastern and northern parts of Colorado, with a few tenths in northern Utah and northeast New Mexico. But other than that, most of the Southwest received no precipitation this week. D0 was trimmed in northeast Colorado, where precipitation improved Standardized Precipitation Index values at several time scales. No change was made to the drought depiction in the rest of the region.