California and National Drought Summary for July 17, 2018
July 19, 2018 - Over the last week, relatively warm weather was common over much of the country, particularly in Kansas, Missouri, Arkansas, Wisconsin, Washington, Oregon, and California. Widespread rainfall fell over parts of Pennsylvania and New York, Illinois, and from southwest Nebraska to the Michigan Upper Peninsula. Elsewhere across the central and eastern United States, rainfall, some moderate to heavy, was generally hit or miss. In the western United States, monsoonal rains fell over Arizona and New Mexico and parts of southern Utah and Nevada, keeping temperatures in the areas receiving rain near or cooler than normal. Most other areas, with the exceptions of eastern Wyoming, the Montana high plains, and parts of Colorado, stayed mostly dry.
Relatively warm temperatures continued in parts of the Northeast this past week, while heavier precipitation fell over parts of West Virginia, Pennsylvania, and New York. As short-term dryness persisted in parts of New England, moderate drought and abnormal dryness continued to expand. Precipitation that fell in northern New York this week prevented further degradation of conditions near the Canadian border. Moderate drought was also introduced north of the Interstate 90 corridor in western New York near Buffalo and Rochester. From central Maryland eastward to southern New Jersey, a very wet May and early June abruptly gave way to a dry and warm weather pattern that led to the abnormal dryness. Parts of this area received heavy rain on Tuesday morning, which will be taken into account for next week’s map.
Aside from cooler conditions along the spine of the Appalachians and mild conditions in most of North Carolina, warmer than normal weather occurred in much of the Southeast over the past week. Heavier rainfall over Alabama allowed abnormally dry conditions near Mobile and in northeast Alabama to improve. Meanwhile, little to no rain fell over parts of North Carolina east of the Appalachians. The ongoing short- and long-term dryness here combined with lowering streamflows led to the expansion of abnormal dryness in central North Carolina. Short-term dryness also led to the expansion of abnormal dryness in parts of coastal South Carolina.
Warmer than normal temperatures occurred over most of the Midwest region over the past week. Heavy rain impacted much of Minnesota and Illinois, while heavy rain was spottier in parts of Missouri, Iowa, Indiana, and Ohio. In several areas that missed out on heavier rainfall, conditions degraded. Extreme drought conditions expanded in northern Missouri into a small part of southeast Iowa, where long-term precipitation deficits and warm conditions led to degrading conditions. Short-term precipitation deficits caused moderate drought to expand in the Michigan Upper Peninsula. Short-term dryness also led to abnormal dryness developing in west-central Missouri. Precipitation deficits and high temperatures led to the development of abnormal dryness over parts of northern Ohio and the southern Michigan Lower Peninsula. Short-term dryness also was noted over localized areas of central and eastern Wisconsin, the latter of which saw conditions degrade to abnormally dry. Short-term dryness ended in most of western Minnesota after a heavy rain event.
Warm conditions over the last week took place in eastern Nebraska, eastern South Dakota, and eastern Kansas. Warm temperatures also occurred over much of western Wyoming and the high plains of Montana. Moderate to heavy rain fell over roughly the eastern half of Wyoming, much of Nebraska (excluding the Omaha and Lincoln areas), and parts of South Dakota and central Kansas. Heavy rainfall Monday night prevented the introduction of abnormal dryness in south-central Nebraska and north-central Kansas, where some long-term precipitation deficits and groundwater shortages are present. Heavy rain this week in parts of central Kansas led to small areal improvements where severe and extreme drought conditions were present. Meanwhile, in areas that mostly missed the rain, short- and long-term deficits caused degradation of conditions. Exceptional drought was introduced in a small area of east-central Kansas, and extreme drought was introduced in the Kansas side of the Kansas City Metropolitan Area and in far southeast Kansas. Conditions remained mostly status quo in Montana and the Dakotas, with a minor improvement from moderate drought to abnormal dryness southwest of Denver, Colorado, due to heavy rain.
Generally warm conditions were found across the South during the last week. Scattered, generally disorganized areas of moderate to heavy rain fell over parts of Oklahoma, Texas (excluding central and south Texas), Louisiana, Arkansas, Tennessee, and Mississippi. Improvements in drought conditions occurred in parts of the Texas and Oklahoma panhandles, while drought expanded in other parts of the panhandles. Extreme drought developed over a small area of northeast Oklahoma as a result of short- and long-term precipitation deficits. Scattered heavy rain over north Texas led to changing drought conditions as many areas that received heavy rain saw improvements to their conditions. Heavy rain in southwest Texas also partially alleviated drought conditions. The hit-and-miss rains in Arkansas, Louisiana, and Mississippi led to small changes in areas of mostly moderate drought and abnormal dryness that were caused by short-term precipitation deficits. In western Tennessee, which mostly missed this week’s heavier rains, conditions continued to dry out in the short term, which may soon lead to abnormal dryness.
Very warm and generally dry weather occurred over the last week in California, Oregon, and Washington. Meanwhile, in southern Nevada, southeastern California, and parts of Utah and Arizona and New Mexico, scattered monsoonal rains continued, leading to localized heavy rains. Because of the short- and long-term precipitation deficits present in much of the region coming into this past week, large amounts of rainfall were needed for drought conditions to improve. Improvements in extreme and exceptional drought conditions occurred over parts of Arizona where enough rain fell to substantially reduce the ongoing deficits. Conditions in Washington continued to dry out in the short term. Combined with warm temperatures, this led to the development of moderate drought in the Olympic Peninsula and the expansion of abnormal dryness in parts of eastern Washington. Abnormally dry conditions also developed in parts of the Idaho Panhandle because of precipitation deficits and low streamflow.
Alaska, Hawaii, and Puerto Rico
In Puerto Rico, recent rainfall led to abnormally dry conditions improving on the southwest part of the island. In Hawaii, continued drier conditions on the Big Island led to the introduction of moderate drought. In Alaska, longer-term deficits built up enough over southeastern Alaska to degrade conditions to moderate drought there.
Over the next 5-7 days, the southern Plains and the Northwest are forecast to remain mostly dry. Rain chances will likely continue over the Southwest, though the focus of the heaviest precipitation will likely be from the mountains in Colorado and New Mexico northeastward into the southern and central High Plains. Rain is also forecast in the northern Plains and Upper Midwest. The best chances for heavy rain amounts during the next week will generally be east of the Mississippi River. The highest chances for warmer than normal temperatures over the next week will be in Alaska, New England, the Florida Peninsula, the Intermountain West, the Desert Southwest, and the Pacific Northwest. In between these areas, the greatest chances for cooler than normal temperatures will occur in the central and northern Plains and in the Upper Midwest.
Curtis Riganti, National Drought Mitigation Center