This U.S. Drought Monitor (USDM) week saw improvement in drought-related conditions across areas of the Southeast, South, Midwest, central and northern Plains, Intermountain West, and Desert Southwest, where short-term precipitation accumulations (past 30-day period) have helped to improve drought-related conditions. For the week, the most significant rainfall accumulations were observed across northern Kansas and areas of the Midwest including Missouri, Iowa, Illinois, and Indiana where accumulations ranged from 3 to 10+ inches, with the highest accumulations observed in northeastern Kansas. On the map, improving conditions over the past 30 to 60 days led to reduction in areas of drought in the Plains states, Kansas to North Dakota, as well as across drought-affected areas across the Midwest. Elsewhere, short-term dryness led to widespread expansion of areas of Abnormally Dry (D0) across the Southeast states including the Carolinas, Georgia, Alabama, and the Florida Panhandle. In the South, drought conditions continued to improve in Texas, including in the Trans-Pecos region in western Texas where short and mid-term composite drought indicators are showing improving conditions in terms of precipitation, soil moisture, and vegetation health. In the West, conditions were generally dry regionally, however, some isolated monsoon thunderstorms provided a much-needed boost in moisture (2 to 3 inch accumulations during the past week) to drought-affected areas of east-central and southeastern Arizona as well as lesser accumulations observed in central and northern Arizona. In terms of reservoir storage in the West, California’s reservoirs continue to be at or above historical averages for the date (July 22), with the state’s two largest reservoirs, Lake Shasta and Lake Oroville, at 105% and 117% of average, respectively. In the Southwest, the U.S. Bureau of Reclamation is reporting (July 21) Lake Powell at 31% full (47% of average for the date), Lake Mead at 31% full (52%), and the total Colorado system (July 20) at 39% of capacity (compared to 45% of capacity the same time last year).
On this week’s map, no changes were made on the map other than the introduction of a small area of Abnormally Dry (D0) in central New York and some reduction of areas of D0 in Maryland and Pennsylvania. For the week, generally light precipitation accumulations (<1 inch) were observed across most of New England, while areas of West Virginia, southeastern Pennsylvania, Maryland, New Jersey, and northern Maine saw higher accumulations ranging from 2 to 3 inches. Average temperatures were near normal to above normal across most of the region, especially in the southern extent, where temperatures were 3 to 5 degrees F above normal. Conversely, areas of the region bordering Canada and the Great Lakes observed below-normal temperatures ranging from 1 to 5 degrees F below normal.
During the past week, light-to-moderate rainfall accumulations were observed across the northern extent of the region in Virginia, North Carolina, and isolated areas of Florida, with the heaviest accumulations (ranging from 3 to 4 inches) occurring in western portions of Virginia, northeastern North Carolina, and north-central Florida. In north-central Florida, this week’s rainfall led to removal of areas of Moderate (D1) and Abnormally Dry (D0) on the map. Conversely, short-term dryness (1 to 6 inches of rainfall deficits during the past 30-day period) led to the expansion of Abnormally Dry (D0) areas in the Carolinas, Georgia, Alabama, and Florida as well as introduction of Moderate Drought (D1) areas in southwestern Alabama, where 30-day rainfall departures ranged from 2 to 5 inches. In terms of average temperatures for the week, the entire region experienced above-normal temperatures, with the greatest anomalies (4 to 6 degrees F) observed across areas of Virginia, the Carolinas, northeastern Georgia, and north-central Florida.
On this week’s map, improvements were made in the Hill Country and Trans-Pecos regions of Texas in response to improving conditions during the past 30-90 days. In these regions, targeted improvements were made in all drought categories (D1-D4). In Tennessee, a mix of degradations and improvements were made on the map in isolated areas of central and eastern Tennessee. For the week, average temperatures were generally above normal in eastern areas of the region, with anomalies ranging from 2 to 8 degrees F. Conversely, the western extent of the region, including much of Texas and Oklahoma, experienced temperatures ranging from 1 to 5 degrees F below normal. Texas reservoirs are reported to be 80% full, with many in the eastern part of the state in good condition (over 90% full), while numerous others in the western portion of the state continue to experience below-normal levels, according to Water Data for Texas (July 23). In terms of streamflow activity (July 23), the U.S. Geological Survey is reporting well above normal streamflows (>90th percentile) across areas of central and eastern Texas, eastern Oklahoma, and north-central Tennessee, while areas of the Texas Gulf Coast and South Texas Plains, northern Louisiana, and southern Mississippi are experiencing below normal levels (1st to 24th percentile range).
Widespread improvements were made across the region in response to beneficial rainfall observed this week as well as during the past 30-day period. Storms during the past week delivered accumulations ranging from 1 to 6 inches, with the heaviest amounts observed in isolated areas of Missouri, Illinois, Indiana, and Kentucky. On the map, improvements were made in Minnesota, Iowa, Wisconsin, Illinois, Indiana, Michigan, and Ohio. For the week, average temperatures were below normal (2 to 12 degrees F) across the northern tier of the region, while the southern extent saw positive anomalies ranging from 1 to 6 degrees F above normal.
On this week’s map, improvements were made in the region, namely in central northern Kansas, southeastern Nebraska, and South Dakota, where shorter-term precipitation (past 30-60 days) was normal to above normal. Additionally, these areas were showing improvements in other drought indicators including soil moisture, streamflow activity, and crop-related vegetation health indices. Conversely, conditions degraded on the map in areas of central South Dakota as well as in northern North Dakota, where dry conditions have prevailed during the past 30 to 60 days. For the week, light-to-heavy rainfall accumulations (ranging from 1 to 10 inches) were observed, with the heaviest amounts impacting northern Kansas and southeastern Nebraska. Below-normal average temperatures (ranging from 1 to 8 degrees F) were logged across most of the entire region.
Out West, generally dry conditions prevailed over much of the region with the exception of isolated areas of the Four Corners states, which observed monsoon-related thunderstorm activity with accumulations ranging from 1 to 4 inches. The storms led to targeted improvements on the map in Arizona. Likewise, isolated areas of the Pacific Northwest and eastern Plains of Montana and Wyoming observed isolated shower activity with accumulations generally of < 2 inches. On the map, persistent dry conditions led to expansion of areas of drought in southeastern Idaho, western Wyoming, and in eastern and southwestern Montana. For the week, average temperatures were mainly below normal with anomalies ranging from 2 to 10 degrees F and the greatest departures logged were observed in eastern Montana.
Puerto Rico, a mix of minor improvements and degradations were made on the map this week.
As the U.S. Virgin Islands await the arrival of the primary rainy season in late summer, short-term abnormal dryness (D0-S) has developed throughout the territory. Showers have been mostly light and scattered in recent weeks, leading to variable stress on crops and native vegetation. Additionally, depth to water at three U.S. Geological Survey wells has generally increased in recent weeks and by July 22 stood at greater than 16.5 feet at the Adventure 28 well on St. Croix and greater than 12.0 feet at the Susannaberg DPW 3 well on St. John. One-month Standardized Precipitation Index values are supportive of D0-S, especially on the northern islands of St. Thomas and St. John. During the drought-monitoring period ending July 22, rainfall totaled less than an inch at all volunteer (CoCoRaHS) and first-order (airport) observation sites, except a couple of locations on St. Croix.
In Alaska, improving conditions led to the removal of the three areas of Moderate Drought (D1) as well as reductions in areas of Abnormally Dry (D0).
In the Hawaiian Islands, rainfall during the past week led to improvements on the map in Maui, Oahu, and Kauai. Rainfall was mainly concentrated in the higher elevations on the windward slopes with the highest weekly total logged in Kauai (17 inches at the Mount Waialeale station).
A very active pattern has developed across the U.S.-Affiliated Pacific Islands in recent weeks, with a potential tropical cyclone (Invest 98W) approaching the Marianas from the southeast at the end of the drought-monitoring period. In advance of Invest 98W’s approach, another week of significant rain in the Marianas eliminated lingering abnormal dryness (D0-S) across Saipan and Tinian. Meanwhile, the Federated States of Micronesia became free of drought, as D1-L was changed to D0-L for Pingelap; more than 5 inches of rain fell across Pingelap from July 19-21. The Republic of Palau and American Samoa are also drought-free. Elsewhere, recent rainfall has chipped away at drought across the Republic of the Marshall Islands, with extreme drought improving to severe drought (D3-S to D2-S) for Utirik and Wotje, and severe drought improving to moderate drought (D2-S to D1-S) for Kwajalein and Ailinglapalap. Severe drought (D2-S) persisted for Jaluit, where month-to-date rainfall through July 20 stood at 6.40 inches, slightly below average. In contrast, July 1-20 rainfall totaled 8.97 inches on Ailinglapalap.
Looking Ahead
The NWS Weather Prediction Center (WPC) 7-Day Quantitative Precipitation Forecast (QPF) calls for relatively dry conditions across the western U.S., areas of the South, and southern Plains. Elsewhere, light-to-moderate accumulations are expected across areas of the central and northern Plains, Northeast, and the Gulf Coast region of the South and Southeast. The Climate Prediction Center (CPC) 6-10-day outlooks call for a moderate-to-high probability of above-normal temperatures across most of the conterminous U.S. with the exception of portions of California and Maine where below-normal temperatures are forecasted. In terms of precipitation, there is a low-to-moderate probability of above-normal precipitation across the Pacific Northwest, northern portions of the Intermountain West, central and northern Plains, Gulf Coast region, and much of the Eastern Seaboard.