Drought Monitor Weekly: Fires Rage in the West, Heavy Rains, Flooding from Sally

Flooded soybean field. Photo: Jeremy Ross, University of Arkansas Extension

Summary

Dozens of dangerous and sometimes deadly wildfires continued to burn across the West, with the greatest concentration of blazes affecting the parched Pacific Coast States. By mid-September, 16 active fires in California, Oregon, and Washington had scorched at least 100,000 acres of vegetation, along with two in Colorado.

At least a dozen active wildfires had destroyed more than 100 structures, while some three dozen fatalities have been reported, with several individuals still unaccounted for.

Farther east, periods of heavy rain (and high-elevation snow) occurred across portions of the Rockies, Plains, and Midwest, boosting topsoil moisture and benefiting drought-stressed rangeland and pastures. However, excessive rain fell in some areas, including parts of Texas, sparking local flooding.

In conjunction with the heavy precipitation, a sharp, early-season cold snap delivered record-setting low temperatures across the Plains, Rockies, and upper Midwest, while summer-like heat lingered along and near the Pacific Coast.

Meanwhile, heavy showers associated with Tropical Storm Sally—later a hurricane—spread across Florida’s peninsula during the weekend of September 12-13. Excessive rain fell in southern portions of the state, including the Florida Keys. Later, as a Category 2 hurricane, Sally made landfall on September 16 near Gulf Shores, Alabama, around 4:45 am CDT, with sustained winds near 105 mph.

Sally dumped historic and catastrophic amounts of rain in southern Alabama and western Florida. In addition, high winds caused extensive damage and power outages along and near the Gulf Coast, while a significant coastal storm surge occurred along and to the east of the landfall location.

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Once inland, Sally exhibited rapid weakening but continued to spark heavy rainfall and flash flooding.

Southeast

Only spotty dryness (D0) exists in the Southeast. With Hurricane Sally moving ashore on September 16 across southern Alabama and drifting northeastward, there is currently much more focus on flooding than dryness.

Still, areas west of Sally’s path have dried out in recent days and will need to be monitored for possible introduction or expansion of dryness. In Huntsville, Alabama, rainfall during the first half of September totaled just 0.06 inch (3% of normal).

South

During the drought-monitoring period, drenching rainfall struck parts of Texas. Abilene, Texas, measured a daily-record sum of 3.80 inches on September 9. Abilene’s 3-day (September 9-11) rainfall reached 4.89 inches, with more than 10 inches reported in a few nearby locations.

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Aggressive improvements were introduced in the hardest-hit areas, which extended northward into Oklahoma. During the week ending September 13, topsoil moisture in Texas improved from 64 to 44% very short to short. Oklahoma’s topsoil moisture rated very short to short improved from 49 to 29%.

Farther east, however, patchy dryness (D0) and moderate drought (D1) existed, particularly in Mississippi, where topsoil moisture rated very short to short stood at 48% on September 13. During the first half of September, rainfall in Mississippi totaled 0.22 inch (13% of normal) in Meridian and 0.03 inch (2%) in Vicksburg.

Midwest

Dramatic drought improvement came to many areas in the form of a multi-day rain event. Measurable rain fell each day from September 6-12 in Iowa locations such as Dubuque and Davenport, totaling 7.46 and 7.76 inches, respectively. During the same 7-day period, Moline, IL, received 5.97 inches.

Broad improvements were introduced where the heaviest rain fell, but some eastern sections of the Midwest remained dry and saw some development or expansion of abnormal dryness (D0). Extreme drought (D3) was erased from Iowa, with only patch of D3 remaining in eastern Nebraska.

In contrast, September 1-15 rainfall totaled just 0.04 inch (3% of normal) in Indianapolis, Indiana, and 0.50 inch (32%) in Saint Louis, Missouri.

High Plains

Mixed signals were apparent in drought-affected sections of the High Plains, as drought impacts were only slightly ameliorated by recent rain and snow. Still, topsoil moisture improved dramatically in Nebraska, from 73 to 45% very short to short, during the week ending September 13.

Even with the precipitation, topsoil moisture on September 13 was rated 72% very short to short in Colorado. In addition, Colorado led the nation—among major production states—in very poor to poor ratings for sorghum (39%) and corn (33%). Wyoming led the region with rangeland and pastures rated 78% very poor to poor.

West

Dry weather dominated the Far West, including California, the Great Basin, the northern Rockies, and the Pacific Northwest, leading to extensive drought intensification as wildfires continued to burn hundreds of thousands of acres and degrade air quality. However, temperatures fell from record-setting levels that had been achieved earlier in the month.

During the heat wave, which peaked amid the previous drought-monitoring period, September 6 was the hottest day ever recorded in California locations such as Woodland Hills (121°F), Paso Robles (117°F), and San Luis Obispo (117°F). Many other communities from California to the Southwest reported record-high September temperatures.

The list of September records set or tied on the 6th included 120°F in Needles, California; 117°F in Riverside, California; 112°F in Gilroy and Lancaster, California; 110°F in Kingman, Arizona, and Stockton, California; 109°F in Sacramento, California; 105°F in Hanksville, Utah; 99°F in Cedar City, Utah; and 91°F in Rock Springs, Wyoming.

Intense heat persisted through September 7 in the San Francisco Bay area, where Gilroy again reached 112°F. Richmond, California, noted its highest-ever temperature (107°F) on the 7th, tying September 15, 1971.

By September 13, USDA topsoil moisture was rated at least 60% very short to short in every Western State except Arizona. Rangeland and pastures rated very poor to poor ranged from 35% in Nevada and Utah to 82% in Oregon.

A new patch of exceptional drought (D4) was introduced along the Nevada-Utah border. Extreme drought (D3) was expanded in several areas, including western Oregon.

However, the eastern edge of the West, mainly from Wyoming to New Mexico, received some much-needed precipitation. In some cases, however, the rain and snow merely staved off further drought intensification.

Still, September 7-8 snowfall in Wyoming totaled 7.5 inches in Casper and 4.7 inches in Lander. Alamosa, Colorado, received an incredible 13.6 inches of snow from September 8-10, breaking a monthly record originally set when 10.0 inches fell on September 27-28, 1936.

Northeast

The meteorological summer (June-August) of 2020 was one of the hottest and driest on record in parts of the Northeast. For example, it was the hottest summer on record in Williamsport, Pennsylvania, where the June-August average temperature of 74.4°F tied a mark originally set in 1904 and achieved again in 2016.

It was the warmest summer in Caribou, Maine, with an average temperature of 66.9°F (previously, 66.3°F in 2018). Caribou also endured its second-driest summer, with just 6.16 inches of rain (54% of normal). The driest summer in Caribou was 1995, with 5.60 inches of rain.

Given the protracted period of heat and dryness, drought continues to expand and intensify in many areas. Two areas of extreme drought (D3) were introduced—one in northern Maine and the other in southern New England. Moderate to severe drought (D1 to D2) was broadly expanded in several areas.

On September 13, topsoil moisture as reported by the U.S. Department of Agriculture was rated 99% very short to short in Maine, along with 94% in New Hampshire and 92% in Rhode Island. Pastures rated in very poor to poor condition ranged from 90 to 100% in Connecticut, Massachusetts, and Rhode Island.

Alaska, Hawaii, and Puerto Rico

Roughly the southern half of Alaska’s Seward Peninsula received significant precipitation, resulting in some trimming of abnormal dryness (D0). Otherwise, the depiction of dryness and drought across northwestern and south-central Alaska remained unchanged.

Meanwhile, two areas of severe drought (D2) were introduced in Hawaii—one on the southern part of Maui and the other in the in Kohala District on the Big Island—due to declining pasture conditions.

There were no changes in Puerto Rico, where a spot of dryness (D0) persists across the southern part of the island.

Looking Ahead

Former Hurricane Sally will drift northeastward, crossing the Carolinas on Friday. Storm-total rainfall in southern Alabama and western Florida could reach 10 to 20 inches, with isolated amounts near 35 inches. Well inland, rainfall could total 4 to 10 inches from east-central Alabama into portions of the Carolinas and southeastern Virginia.

Meanwhile, Sally’s storm-surge and wind-related impacts will continue to subside. Most of the remainder of the country will experience dry weather during the next 5 days, although a series of cold fronts will deliver some precipitation from the Pacific Northwest to northern sections of the Rockies and High Plains.

Parts of southern Texas will also receive rain. Elsewhere, a surge of cool air will affect much of the South, East, and Midwest, while generally warm weather will cover the West. However, by week’s end and early next week, warmth will replace previously cool conditions across the northern Plains and upper Midwest.

The NWS 6- to 10-day outlook for September 22 – 26 calls for the likelihood of cooler-than-normal conditions in most areas along and east of a line from central Texas to Lake Ontario, while above-normal temperatures will dominate the Plains, West, and upper Midwest.

Meanwhile, wetter-than-normal weather in the Four Corners region, Deep South Texas, and the Pacific Northwest should contrast with near- or below-normal precipitation across the remainder of the country.




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