Nationwide
There were significant changes in the Drought Monitor depiction of dryness and drought this week compared to last, primarily across the contiguous U.S. east of the Mississippi River.
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Inundating tropical rains washed away the entrenched moderate to severe drought (D1 to D2) that had covered southern Florida.
The opposite was the case farther north across most of the Eastern States. Rainfall has been generally below average across a majority of this region for the past 1 to 2 months, with subnormal rainfall dating back three or more months in some areas. Increasingly, above-normal temperatures have accompanied the dryness, adding to the surface moisture depletion rate. Temperatures have had the most significant impact on conditions in the climatologically hotter areas across the South until late this past week when excessive heat started to engulf the Great Lakes and Northeast. Declining streamflows and dropping soil moisture became apparent this past week over large sections of the East. As a result, there was an expansive increase in new D0 coverage east of the Mississippi River and north of central Florida, with only small spots in Georgia and Maine experiencing any discernable relief.
Although changes were not as expansive in the farther West, south-central and north-central portions of the Plains and Rockies also saw significant areas where dry conditions developed or intensified. There were other areas of heavy rain outside southern Florida, but most of it fell on sections of the Upper Midwest that have received consistently above-normal precipitation for at least several weeks, thus bringing no changes to areas of dryness and drought. West of the Mississippi River, limited improvement was introduced in relatively small swaths in northeastern Arkansas, central and western Kansas, southern Nebraska, southwestern Montana, and a few adjacent locales.
The West
Conditions were seasonably dry in this broad region, so very few changes were made in sharp contrast to areas farther east.
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However, one area of deterioration was in part of New Mexico, based on high wildfire danger and ongoing fires threatening dwellings and other structures near Ruidoso. Unusually dry, hot, and windy weather combined with low fuel moisture are abetting favorable conditions for the rapid development and spread of wildfires near and south of Ruidoso, so the D1 through D3 areas in this region were expanded somewhat to the northwest. Meanwhile, improving soil moisture and some recent light to moderate precipitation – especially at higher elevations – prompted improvement from moderate drought (D1) to D0 in southwestern Montana and a small part of adjacent Wyoming.
The High Plains
Moderate to heavy rains soaked a sizeable part of the High Plains Region last week. Most fell on locations not experiencing antecedent dryness and provided no relief, but several areas entrenched in drought did record enough rainfall to consequentially improve conditions.
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Heavy rainfall totals of 2 to locally 4 inches were fairly common over a fairly broad swath from northeastern to southwestern Kansas, making this one of the few states to experience more relief than deterioration last week. Patches of 1-category improvements were introduced where heavier rains fell, continuing a trend of decreasing dryness observed since mid-May. At that time, almost one-third of the state was covered by severe drought (D2) or worse. Four weeks later, less than 8 percent of the state is similarly dry. Farther north, heavy rains also affected parts of areas experiencing antecedent dryness in southern Nebraska. Generally, 1 to 3 inches of rain eliminated moderate drought (D1) in south-central Nebraska and whittled away some D0 in some other parts of south-central Nebraska. Moderate to heavy rains also ended D0 conditions in a few small areas in central South Dakota as well.
Farther west, however, continued dry and warm weather engendered areas of deterioration in central portions of the Rockies and High Plains, as has been scattered across these areas occasionally for the past several weeks. Burgeoning 60- to 90-day precipitation shortfalls and acute root-zone moisture and groundwater deficits led to a broad expansion of moderate drought (D1) in eastern Wyoming and western Nebraska. The dry week, compounded by recent heat and increasing short-term precipitation shortfalls, also led to lesser D0 and D1 expansion in other parts of Wyoming and a few areas across Colorado and the central and western portions of South Dakota.
The South
D0 expansion was also observed in this region, but primarily near and east of the Mississippi River and not nearly to the extent seen farther north and east.
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New, relatively small areas of D0 were brought into south-central Tennessee and part of east-central Tennessee, with abnormal dryness expanding from the areas covered last week into somewhat larger parts of north-central Mississippi and portions of northern and western Arkansas. In contrast, light to moderate rains (up to 1.5 inches) eased brought just enough relief to prompt 1-category improvements in parts of northeastern Arkansas, and scattered moderate rains (1 inch or more) with isolated heavy amounts (up to 3 inches) moistened parts of the northeastern fringes of the D0 region in central Texas, and some patches in eastern New Mexico and western Texas.
Meanwhile, growing short-term deficits have begun to quickly reduce surface moisture levels in western Oklahoma east of the Panhandle, so this entire region has been placed in moderate drought (D1). Streamflows declined significantly this past week, with several locations reporting flows more indicative of D2 to D4 conditions if no other parameters were considered, especially over the southern half of this area. Declining streamflows and increasing short-term rainfall deficits prompted new D0 areas in parts of northern and western Arkansas where little or no rain fell last week, and similarly, low streamflows were observed in parts of this region as well. — UNL Drought Monitor
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