A large shift in the weather pattern occurred this week across the lower 48 states. Early in the week, low pressure exited the Great Lakes region, allowing temperatures to gradually moderate during the latter half of the week across portions of the eastern contiguous U.S.
In the western CONUS, high pressure broke down as a strong storm system moved into the Pacific Northwest heading into the weekend. As this storm system moved eastward into the Great Plains through the weekend and leading up to Oct. 25, many locations across the western and central CONUS experienced above-normal precipitation, with cooler than normal temperatures in the system’s wake.
However, with surface high pressure early in the week followed by southerly flow ahead of the storm system, warm temperatures dominated much of the central CONUS for the week as whole, with above-normal average temperatures also extending northeastward into the Great Lakes and Northeast.
Unfortunately, given the expanse of drought and abnormal dryness across the U.S., antecedent dryness led to another week of degradations for many not receiving rainfall, even in areas where temperatures were cooler than normal this week. Warm conditions and high winds further exacerbated conditions in drier areas across the Great Plains. Fortunately, in areas seeing the heaviest rainfall amounts, particularly across the Southern Plains and Ozarks, some improvements were also warranted.
South
A storm system moving out of the Rockies and intensifying across the Southern Plains dropped in excess of 2 inches of rainfall in a large swath from northeastern Texas to the western Ozarks, warranting 1-category improvements across many of these locations. In surrounding areas that received heavier precipitation amounts, improvements were more targeted in nature, as amounts were not enough to eliminate 90-day deficits. Farther eastward, from the Lower Mississippi Valley to the Tennessee Valley, antecedent dryness and a drier than normal week resulted in another round of widespread 1-category degradations.
Midwest
In similar fashion as the Southern Region, antecedent short-term (30- to 60-day) dryness has resulted in the widespread expansion of abnormally dry (D0) and moderate (D1) to severe (D2) drought conditions. Given the much of the region experienced above-normal temperatures and below-normal precipitation again this week, it warranted another round of 1-category degradations, particularly across the Ohio Valley.
Soil moisture ranks in the bottom 20% of the historical distribution, according to various soil moisture products. In addition, 30 to 60-day standardized precipitation indices (SPIs) range anywhere from D1-equivalent (moderate drought) to D4-equivalent (exceptional drought), with 30-day SPIs indicating the more severe designations.
Parts of Missouri and the central Corn Belt were the only areas that received enough rainfall to improve drought conditions or stop ongoing degradation this week. More than 2 inches of rain fell across the western Ozarks leading to broad 1-category improvements to the drought depiction in affected areas, as rainfall totals improved short-term precipitation deficits and topsoil moisture and 7-day average stream flows responded favorably.
High Plains
Above-normal temperatures, below-normal precipitation, and periods of high winds resulted in degradations to ongoing D1 (moderate) to D4 (exceptional) drought across the Central Plains, east of the Front Range. Stock ponds for cattle remain low to non-existent and pastures are providing marginal feed, with supplemental feed required for many.
Conversely, the storm system that moved across the Intermountain West during the weekend dropped heavy precipitation across the higher elevations of Wyoming and Colorado and parts of the Northern High Plains from Montana eastward to North Dakota. Unfortunately, even though several areas experienced in excess of 1 inch of precipitation (greater than 1.5 inches for many locations across the Northern High Plains), short to long-term drought indicators did not show many signs of improvement by Oct. 25. Only surface soil moisture showed some improvement, with sparse 7-day average stream flows also improving, corroborated by ground reports. As such, given the lack of response in the indicators, much of the Northern High Plains remain unchanged this week.
West
A strong storm system moved into the western U.S. heading into the weekend and moved across the Intermountain West leading up to Oct. 25. Many locations across the Pacific Northwest, Great Basin, and the Rockies received in excess of 0.5 inches of rainfall, with the heaviest amounts (greater than 1 inch, with locally higher totals) concentrated across the Pacific Northwest, Idaho, and Montana. Precipitation was not enough to improve drought conditions in the Pacific Northwest, but was enough to halt another week of degradation along the windward slopes of the Cascades and Coastal Ranges. Only areas east of these ranges, in the rain shadows, experienced some targeted degradations. Farther south, D2 (severe) drought degraded to D3 (extreme drought) north of San Francisco, where USGS 28-day average stream flows have fallen below the 2nd percentile of the historical distribution, CPC soil moisture indicates D4-equivalent (exceptional drought) conditions, and the long-term objective drought blend depicts D3 conditions. Elsewhere, localized and targeted improvements were made across the Intermountain West, based on 7-day precipitation totals and improvements short-term precipitation deficits.
