Map released Sept. 10, 2020 | Data valid Sept. 8, 2020
This week’s drought summary: Intense heat, low humidity, gusty winds, and little or no rain allowed for broad-scale drought intensification in most of the Central Great Plains and from the High Plains to the Pacific Coast. Conditions took a dramatic turn across the Rockies and Plains as the valid period ended, with hot and dry conditions suddenly replaced by much colder weather, and snow in some areas. A number of sites from the central Rockies into the northern Plains saw temperatures drop from around 90 degrees F Labor Day to near freezing with light snow the next morning. Denver, CO went from temperatures averaging 15 degrees above normal on Sept. 6 to 30 degrees below normal for Sept. 8, with an inch of snowfall reported. East Rapid City, SD appears to have set a national all-time record by going from over 100 degrees F (102) to reporting measurable snow in a span of 2 days. The colder and wetter weather that developed just as the period ended had little impact on drought conditions in most areas, given the hot, dry, and windy conditions that preceded it.
Wildfires continued to scorch and spread rapidly across parts of California, with some quickly breaking out and expanding in part of the Rockies as well. Denver, CO went from reporting reduced visibility due to wildfire smoke on Labor Day, to reduced visibility from falling snow the next morning.
Elsewhere, several inches of precipitation across interior Northeastern Texas, in a swath from eastern Iowa to central Illinois, across Ohio, and in parts of Arkansas brought significant drought relief, and lesser amounts in adjacent areas brought more limited improvement, as did moderate precipitation in parts of the Northern Rockies and adjacent Plains.
South: Heavy rain soaked a large area across Northeastern Texas, dramatically easing or ending drought and abnormal dryness. Some two-category improvements were noted in the wettest areas. Heavy precipitation was less widespread in Arkansas and some adjacent areas, reducing the extent of abnormal dryness there. Across West Texas and farther east in Mississippi, dryness and drought expanded and intensified. Much of West Texas is now in extreme drought, with a small area of exceptional D4 drought in the interior Big Bend area. Parts of this region have received only a few tenths of an inch of precipitation since early August. Moderate drought was introduced in part of interior northeastern Mississippi where less than half of normal rainfall was recorded during the last 60 days.
Looking ahead: During the next five days (Sept. 10-14), WPC’s QPF forecasts little or no precipitation (and thus persisting or intensifying drought) across the Northern Plains and most areas from the Rockies to the Pacific Coast, save higher elevations in New Mexico and Southern Colorado (0.5 to 1.5 inch). Similarly, light precipitation at best is expected across southern half of the Mississippi Valley and the western Ohio Valley. The heaviest precipitation (two to four inches) is expected in a broad swath from Southwest Oklahoma through much of the Rio Grande Valley. Farther north, between 1.5 and 2.5 inches are expected from northern Missouri northeastward into western Wisconsin – part of a broader area expecting over 0.5-inch through much of Central and West Texas, the Central Great Plains, the Upper Mississippi Valley, and most of the Great Lakes region. Moderate precipitation, from 0.5 to 1.5 inches, should cover most of New England, New York, and the dry portions of Pennsylvania. Similar amounts are expected in the Southeast from Alabama eastward, with heavier amounts (1.0 to locally 2.5 inches) forecast in the Carolinas.
From the central Gulf Coast through most of the Eastern U.S., near-normal daytime temperatures should average a few degrees above normal at night. Temperatures should average a few degrees below normal from the southeastern Rockies through most of the central and southern Plains and the Great Lakes region, but near- to somewhat above-normal across most of the northwestern quarter of the country.
The Climate Prediction Center’s 6-10-day outlook (Sept. 15-19) favors above-normal rainfall from the Ohio Valley, Middle Mississippi Valley, and Central Texas eastward to the Atlantic Coast. Wet weather is also expected in the Northwest while odds again favor subnormal precipitation in much of the Great Basin, Four Corners States, and northern half of the Plains. In addition, surplus moisture is expected along the southern tier of Alaska, but subnormal precipitation is anticipated in the northern reaches of the state. Portions of Central and Southwestern Texas, plus Eastern Alaska, should record below-normal temperatures while the near- to above-normal readings prevail elsewhere.