Weather Summary: The week commenced with high pressure over the Southeast and storm systems traversing across the northern U.S. As the week progressed, the high pressure system traveled westward, settling over the south-central Plains while a trough of low pressure and associated cold front brought scattered showers and thunderstorms to the eastern third of the Nation. A weak frontal system generated scattered showers in the Pacific Northwest. In the Southwest, tropical moisture from Tropical Storm Juliette (which dissipated off central Baja California) helped to fuel the southwest monsoon in Arizona, Nevada, Utah, and southern Idaho. Decent showers also fell on parts of New Mexico and Colorado. Hit and miss showers also fell on parts of the northern Plains and upper Midwest, the central Great Plains, and south-central Texas. Unsettled weather and decent precipitation also affected most of Alaska, with many stations reporting weekly totals exceeding 2 inches in southwestern and south-central sections of the state. In contrast, little or no rain fell on most of California, Oregon, and eastern Washington, parts of the Plains, most of the Mississippi Valley, and much of Hawaii. Weekly temperatures averaged well above normal (6 to 10 degF) across much of the contiguous U.S., with the exception of seasonable readings in the desert Southwest and Southeast. Highs topped triple-digits in the southern two-thirds of the Plains, southern Iowa and northern Missouri…
Northern and Central Great Plains: Most of the Dakotas reported light to moderate (0.5 to 1.5 inches) of rain, with a few spots in southern North Dakota and northern South Dakota measuring over 2 inches. The rains were enough to keep conditions status-quo, except where the heavier rains fell. In the latter case, D0 was alleviated along most of the western D0 edge of the Dakotas, with D1 to D0 in south-central North Dakota. A slight increase in D0 was made in extreme southeastern South Dakota where many days in the 90’sF have started to prematurely brown the crops. USGS stream flows are still near or above normal at most sites in the Dakotas. No changes were made in Nebraska and Kansas, except for a small 1-category improvement (D1 to D0; D0 to nothing) in extreme sections of southeast Nebraska, northeast Kansas, southwest Iowa, and northwest Missouri, where 1.5 to 3.2 inches fell.
Southern Great Plains: In Oklahoma and Texas, several weeks of mostly dry and warm weather (highs in the 100sF) have diminished the surplus rains from a wet and cool July (in both states) and a wet and cool early August (in Oklahoma). As a result, D0 returned across northern Oklahoma, while a 1-category downgrade occurred across southern Oklahoma as August was a no-show in the southern third of the state. In Texas, a band of light to moderate, with some locally heavy (>2 inches) rain, fell from near Del Rio northeastward into southeastern Oklahoma, and along the Gulf Coast. Some slight improvements were made where the heaviest totals occurred. In eastern Texas, little or no rain fell, and some deterioration was made.
The Southwest: A continued robust summer monsoon, aided by a northward fetch of moisture from former Tropical Storms Juliette and Kiko (both dissipated west of central Baja California), produced widespread showers and thundershowers to much of Arizona, New Mexico, Nevada, Utah, and northward into parts of the West (Idaho, Wyoming, and Colorado). Numerous locations in southern Nevada and Arizona measured over 2 inches of rain, while 1 to 2 inches were common in central Nevada, western and central New Mexico, central Utah, and most of Arizona. Although short-term shortages have been greatly eased or eliminated, long-term deficits still lingered. To accommodate the long-term impacts, only slight improvements were made where the greatest rains fell and the long-term deficits (180-days) were noticeably reduced. For example, enough rain has fallen during the past 6-months in western New Mexico and southwestern Texas that surpluses have accumulated, hence the D2 to D1 and D0 to nothing upgrade, respectively. Similarly in south-central Nevada, D3 and D2 was improved where there was heavy weekly rains and the 180-day deficits were noticeably diminished. The same holds true in western and central Arizona where D2 and D1 were decreased. On Sep. 2, even many USGS stream flow gauges in western New Mexico, central Arizona, southern Nevada, and southwestern Utah flowed at the 90th percentile at 1- and 7-days. The Impacts line was redrawn to depict improved short-term conditions from the robust monsoon, making the long-term (hydrologic) effects causing most of the negative impacts.
The West: Moderate to heavy (1 to 3 inches) rains fell on the Pacific Northwest Coast, effectively eliminating the D0(S) in western Washington. Southwest monsoonal showers also spread northward into southeastern Idaho, central Colorado, and southeastern Wyoming, dropping enough rain (1 to 2.5 inches) to improve D2 to D1 in southeastern Idaho, and 1-category improvement of parts of the D3 and D2 areas in southeastern Wyoming. In addition, 180-day surpluses were present, justifying an upgrade from D1 to D0. Elsewhere, little or no rain fell, and conditions were kept status-quo. An exception was made in north-central Oregon (D0 and D1) where a re-assessment of 90- to 180-day deficiencies were made. The data and products yielded a surplus at those time periods, hence the D1 was improved to D0 (eastern Wheeler county) and D0 removed (from Wasco, Jefferson, Sherman, and western Wheeler counties).