Heat and dry conditions story of the High Plains

The latest U.S. Drought Monitor saw very hot and dry conditions across areas of the western U.S. and the Plains states.

Average temperatures soared well above normal levels—significantly elevating evaporate demand, especially across the Upper Midwest, Northern Plains, Colorado, and the Texas Panhandle where conditions deteriorated rapidly. Elsewhere, heavy rains across areas of the Mid-Atlantic states, Southeast, and the South, led to widespread improvements on the map in drought-affected areas.

In the Upper Midwest, drought expanded and intensified on the map, especially across Minnesota and Wisconsin where composite flash drought indicators were showing severe to extreme flash drought conditions during the past week. Out west, the Four Corners states continued to receive beneficial monsoonal rainfall with isolated areas receiving 2 to 4 inches.

In portions of Arizona and western New Mexico, precipitation during the past 30-day period has been above normal, boosting streamflow and soil moisture levels while improving vegetation health.

In terms of reservoir storage in the West, California’s reservoirs continue to be at or above historical averages for the date (July 28), with the state’s two largest reservoirs, Lake Shasta and Lake Oroville seeing slight decreases over the past week, at 99% and 108% of average, respectively. In the Southwest, the U.S. Bureau of Reclamation is reporting (July 26) Lake Powell at 23% full (33% of average for the date; lowest on record for the date in the last 30 years), Lake Mead at 27% full (45% of average for the date; lowest on record for the date in the last 30 years), and the total Colorado River system (July 26) at 33% of capacity (compared to 39% of capacity the same time last year).

According to the Salt River Project, the Salt River reservoir system in Arizona is currently 48% full, Verde River system 59% full, and the total reservoir system at 50% full (compared with 59% full a year ago).

The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the U.S. Department of Agriculture and the National Oceanic Atmospheric Administration. (Map courtesy of NDMC.)

South

In southern Texas, areas of drought expanded where hot and dry conditions have prevailed during the past 30 days. In the Texas Panhandle, short and longer-term dryness led to intensification of drought with year-to-date precipitation deficits ranging from 3 to 8+ inches.

Looking at the reservoir situation, Water Data for Texas (July 29) reports statewide reservoirs at 78% full, with eastern reservoirs in good condition while numerous western, northern (Panhandle), and southern reservoirs remain below normal. Looking at climatological rankings for the past 30-days, record to near-record mean temperatures were observed in areas of the region, including in Brownville, Texas (second warmest on record, +2 degrees Fahrenheit departure), and Amarillo, Texas (eighth warmest, +3 degrees departure). Average temperatures for the week were above normal across most of the region (1 to 10 degrees) with the greatest anomalies observed in the panhandles of Oklahoma and Texas.

Midwest

Widespread degradations were made on the map across the northern portions of the region including Minnesota, Iowa, Wisconsin, and Illinois. In terms of rainfall for the week, much of the region was dry and well above normal temperatures were observed in Minnesota with 2- to 8- degree departures.

Additionally, NDMC’s flash drought composite map (July 27) showed flash drought conditions developing across areas in the Upper Midwest including Minnesota, Wisconsin and Michigan. Looking at climatological rankings for the past 30-day period, numerous locations ranked among their warmest or near warmest mean temperatures on record, including Hibbing, Minnesota (warmest on record, +6 degrees departure); Minneapolis/St. Paul Airport (second warmest, +5 °degrees departure); Dubuque, Iowa (second warmest, +5 degrees departure); Eau Claire, Wisconsin (second warmest, +4 degrees departure); and Milwaukee, Wisconsin (fourth warmest, +3 degrees departure).

High Plains

For the week, drought-related conditions deteriorated across the region including in the Dakotas, Nebraska and Kansas where temperatures were well above normal, especially in western portions of the region where anomalies ranged from 3 to 9 degrees above normal.

NDMC’s flash drought composite map (July 27) also showed flash drought conditions developing with numerous drought impact reports coming into the NDMC’s Condition Monitoring Observer Report reporting system during the past seven-day period—especially in the Dakotas in relation to crop and rangeland conditions. Looking at climatological rankings for the past 30-day period, numerous locations ranked among their warmest or near warm

st mean temperatures on record, including: Rapid City, South Dakota’s National Weather Service’s Weather Forecast Office, (warmest on record, +8 degrees departure); Custer, South Dakota (third warmest, +6 degrees departure); Bismarck, North Dakota (fifth warmest, +5 degrees departure); and Fargo, North Dakota (third warmest, +5 degrees departure).

West

On the map, drought-related conditions deteriorated in areas of eastern Colorado, eastern New Mexico, southeastern California, and western Washington.

Conversely, beneficial monsoonal rainfall led to improvements across Arizona, northwestern New Mexico, southeastern Utah, and northeastern Nevada. In the Southwest, an active monsoonal pattern (June 15 to present) has led to above-normal precipitation, especially in Arizona where percentages of normal have ranged from 150% to 250% above normal across southeastern, central, and northern portions of the state.

In Colorado, drought expanded and intensified on the map in response to anomalously warm temperatures, decreased soil moisture levels, and elevated evaporative demand. Looking at climatological rankings for the past 30-day period, numerous locations ranked among their warmest or near warmest mean temperatures on record, including: Montrose (warmest on record, +3 degrees departure); Dinosaur (warmest on record; +4 degrees departure); Grand Junction (second warmest, +4 degrees departure); Trinidad (second warmest, +4 degrees departure); and Denver (second warmest, +3 degrees departure). In Wyoming, Rock Springs (third warmest, +4 degrees); and Casper (third warmest, +5 degrees departure.)

Looking ahead

The NWS Weather Prediction Center’s 5-Day Quantitative Precipitation Forecast calls for the heavy precipitation accumulations across portions of the Gulf Coast from southeastern Louisiana to west-central Florida, where totals ranging from 3 to 5+ inches are expected.

In the Midwest, and eastern portions of the High Plains, precipitation accumulations generally ranging from 1 to 4+ inches are expected. In the Four Corners states, isolated monsoonal rainfall with accumulations ranging from 1 to 2 inches are forecast, while dry conditions are expected across most of the Intermountain West, Great Basin, and West Coast states.

The NWS 6-10-Day Temperature Outlook, valid August 3 to 7, favors above-normal temperatures across most of the contiguous United States, with the highest probabilities centered across California, the Great Basin, Desert Southwest, and portions of the central and southern Rockies.

Above-normal temperatures are also favored across the Plains, Midwest and South. Near-normal temperatures are favored across portions of the Pacific Northwest and central Gulf Coast.

The NWS’s 6- to 10-Day Precipitation Outlook favors above-normal precipitation across portions of the Southwest, western and southern Texas, southern Florida, Upper Midwest, and the Northeast.

Below-normal precipitation is favored across portions of the northern Rockies, northern Great Basin, and western portions of the Plains states. Elsewhere, near-normal conditions are expected.

David Simeral is with WRCC/DRI.