Nationwide
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The U.S. experienced the extremes this week, with an expansion of drought in the West, a robust Southwest Monsoon, a tropical storm making landfall in the Southeast, and extreme flooding in southeastern Texas.
In the West, mid-level ridging has resulted in much above-normal temperatures for the western third of the contiguous U.S. (CONUS), exacerbating drought conditions in the Pacific Northwest, northern Great Basin, Northern Rockies, and along the Front Range. Above-normal temperatures also pushed into the northern High Plains, warranting further deterioration of drought conditions in locations where rainfall remained below-average for the week.
The central and eastern Corn Belt was a battleground of sorts, with some locations seeing improvement with this week’s heavy rainfall, while other locations missed out, warranting some degradation due to antecedent dryness.
New Mexico and West Texas saw targeted reductions in drought coverage due to heavy precipitation associated with the robust Southwest Monsoon.
In the eastern U.S., Tropical Storm Elsa made landfall and moved up the East Coast, leaving in its wake a large swath of more than 2 inches of rainfall, with several locations receiving 5 to 10 inches of rainfall. The extra-tropical transition of Elsa warranted moderate drought (D1) removal along the Virginia/North Carolina border with 1-category improvements elsewhere along Elsa’s path up the East Coast. Frontal activity prior to Elsa’s passage warranted improvements to interior areas of the Northeast.
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The West
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Extreme, record-breaking heat leading up to this week has resulted in rapid deteriorations in drought conditions across the Pacific Northwest, northern Great Basin, and Northern Rockies. Although the largest positive temperature anomalies shifted southward into the Desert Southwest and Four Corners Region this week, above-normal temperatures persisted across the northwestern CONUS, resulting in continued degradations of drought conditions from the Pacific Northwest eastward to central Montana. A small area of improvement was warranted in northeastern Montana, where 1 to 2 inches of rainfall resulted in modest improvements to soil moisture and short-term Standardized Precipitation Indexes (SPI).
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Farther southward in New Mexico, the robust Southwest Monsoon has resulted in drastic improvements in recent weeks. This week is more of the same, with several 1-category improvements across central and eastern portions of the state. In some cases, moisture has seeped several feet into the soils, at least down to 200 cm (per NASA SPoRT and ground reports). Improved shallow groundwater conditions also support the improved depiction this week. However, fire concerns remain across the West as a whole, as nearly 40 new wildfires have been reported since July 10 (89 as of July 14).
The High Plains
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The western half of the High Plains Region experienced above-normal average temperatures this week underneath a mid-level ridge, while the eastern half experienced below-normal average temperatures, associated with increased cloud-cover and heavy rainfall for several locations.
Improvements were mainly designated to the Middle Missouri River basin, encompassing parts of eastern South Dakota and northeastern Nebraska, which received more than 2 inches of rainfall (more than 1 inch above-normal for the week). Elsewhere in the Dakotas, Nebraska, and Kansas, below-normal precipitation coupled with antecedent dryness warranted several 1-category deteriorations.
In the western half of the High Plains Region, deteriorations were more a function of above-normal temperatures helping to exacerbate ongoing drought conditions in the Eastern Rockies and along the Front Range. Furthermore, this region is void of snowpack due to the below-normal rainy season in the West leading up to this period of above-normal temperatures since Spring, which has caused further depletion of soil moisture, stream flows, and groundwater in many locations.
The South
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A localized area of low pressure brought severe flooding to much of southeastern Texas, with many locations in and around the Houston metro area receiving 10 to 15 inches of rainfall. Some of the precipitation associated with this system made it farther westward, resulting in 1-category improvements (D0 and D1) along the Rio Grande.
Western Texas, and extending into New Mexico, is experiencing improved ground conditions with this week’s rainfall and antecedent conditions related to the early onset and robustness of the Southwest Monsoon, warranting 1-category improvements in the Trans-Pecos region and western parts of the Panhandle.
Farther east in the Tennessee Valley, D0 coverage was reduced for many locations receiving 2 inches or more rainfall. However, where the heavier amounts were not observed, short-term deficits continue to mount, with parts of northeastern Tennessee experiencing an expansion of abnormally dry (D0) conditions, with a small area deteriorating to moderate drought (D1) conditions where 90-day deficits have increased to around 6 inches. — UNL Drought Monitor
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