‘Flash drought’ in High Plains

Tropical Storm Beta made landfall on Sept. 21 about 10 p.m. CDT near Port O’Connor, Texas, with sustained winds near 45 mph. Once inland, slow-moving Beta weakened and turned northeastward, crossing the Mississippi Delta before dissipating on Sept. 25 over the Southeast. Nevertheless, heavy rainfall associated with Beta caused local flooding, especially along and near the middle and upper Texas coast. Beta’s heavy rain tracked across an area (centered on Mississippi) experiencing abnormal dryness (D0) and moderate drought (D1), leading to a significant boost in soil moisture.

Mostly dry weather covered the remainder of the country, aside from a few showers in the upper Great Lakes region and some beneficial precipitation in the Northwest. Across much of the Plains and Midwest, open weather favored agricultural fieldwork but further reduced topsoil moisture in drought-affected areas. In fact, worsening drought remained a major concern across much of the western half of the country, with adverse impacts on rangeland and pastures. In addition, the return of hot, windy weather fanned several new Western wildfires. Near- or above-normal temperatures prevailed in the West, with the hottest weather occurring in the Four Corners States. As the drought-monitoring period ended on Sept. 29, approaching heavy rain brought the promise of relief to the Northeast, enduring its second major drought in 5 years.

High Plains

Dry, occasionally breezy weather led to a “flash-drought” situation, with rapid development or expansion of dryness and drought. Several days of summer-like warmth contributed to the drying; in Nebraska, daily-record highs rose to 95°F in Valentine (on Sept. 22) and North Platte (on Sept. 23). On Sept. 24, East Rapid City, South Dakota, noted a daily-record high of 93°F. By Sept. 27, topsoil moisture across the region rated very short to short ranged from 49% in Kansas to 77% in Colorado. Wyoming led the region with rangeland and pastures rated 64% very poor to poor. Colorado producers had planted 66% of their intended winter wheat acreage by Sept. 27, leading the nation (and 9 percentage points ahead of the 5-year average), but only 19% of the crop had emerged (8 points behind average). These statistics—rapid planting but slow emergence—were indicative of dry conditions.

South

The remnant circulation of Tropical Storm Beta tracked across the area of abnormal dryness (D0) and moderate drought (D1) centered on Mississippi. Sept. 21-24 rainfall topped 4 inches in locations such as Natchez, Mississippi (5.35 inches); Monroe, Louisiana (4.83 inches); and Texarkana, Arkansas (4.13 inches). Following Beta’s passage, D1 was eliminated from Mississippi. However, southeast of Beta’s area of influence, parts of eastern Mississippi saw mounting short-term precipitation deficits and a corresponding increase in D0 coverage. Farther west, parts of central Texas continued to benefit from recent heavy rainfall, while conditions rapidly worsened across the High Plains of Texas and Oklahoma. In fact, two new areas of exceptional drought (D4) were introduced in western Texas. Through Sept. 29, year-to-date precipitation in Midland, Texas, totaled just 6.84 inches (59% of normal). In Texas’ northern panhandle, year-to-date precipitation had not yet reached the 9-inch mark in Borger and Dalhart. Borger’s 8.87-inch total was 48% of normal. On Sept. 27, Texas led the country—among major production states—in cotton rated very poor to poor (35%). Oklahoma led the nation with 47% of its sorghum rated very poor to poor, according to USDA.

Midwest

Despite scattered showers, mainly in the Great Lakes region, some areas continued to experience an expansion of short-term dryness (D0) and moderate drought (D1). Sept. 1-29 rainfall totaled just 0.12 inch (4% of normal) in Indianapolis, Indiana, and 0.90 inch (30%) in Saint Louis, Missouri. However, many farmers welcomed the open weather during harvest season. For example, the nation’s soybean harvest was 20% complete by Sept. 27, compared to the 5-year average of 15%.

West

Precipitation in the Pacific Northwest aided wildfire containment efforts and brought slight improvement in the drought situation, mainly west of the northern Cascades. However, the remainder of the West remained warm and dry, with gusty winds and low humidity levels contributing to another round of dangerous wildfire activity in northern California. The much-needed Northwestern precipitation delivered daily-record amounts on Sept. 23 in western Washington locations such as Hoquiam (1.32 inches); Olympia (1.23 inches); and Seattle (1.08 inches). Troutdale, Oregon, reported more than an inch of rain on Sept. 18, 23, and 25—with totals of 1.13, 1.18, and 1.02 inches, respectively. Precipitation spread as far inland as the northern Rockies; in Idaho, daily-record totals included 0.55 inch (on Sept. 25) in Stanley and 0.54 inch (on Sept. 26) in McCall. Farther south, several new patches of exceptional drought (D4) were introduced or expanded in Colorado, New Mexico, Arizona, and Utah. As the water year (Oct. 1, 2019 – Sept. 30, 2020) came to an end, extreme drought (D3) was expanded in northern California and portions of neighboring states. California’s two most dangerous new wildfires were the Glass and Zogg Fires, both of which started on Sept. 27. The Glass Fire, in Napa and Sonoma Counties, and the Zogg Fire, in Shasta County, both scorched about 50,000 acres of vegetation a couple of days, with little containment. Meanwhile, very poor to poor ratings were indicated by USDA on Sept. 27 on at least 50% of rangeland and pastures in all Western States except Idaho, Nevada, and Utah, led by Oregon (82% very poor to poor). On the same date, topsoil moisture was at least 60% very short to short in every Western State except Arizona, led by New Mexico (86% very short to short).