Extensive drought degradation noted in High Plains

This U.S. Drought Monitor week saw extensive degradations across areas of the West, Plains, South, and Southeast.

In the South and Southeast, dry conditions persisted, adding to significant longer-term (9- to 12+ month) precipitation deficits (ranging from 8 to 20+ inches), with the most severe drought conditions centered over portions of Texas, Arkansas, Georgia, and Florida.

At the end of March, mountain snowpack conditions remain well below normal for the time of year, with record to near-record low levels observed across all western states. Additionally, many Natural Resources Conservation Service SNOw TELemetry (SNOTEL) network monitoring stations are reporting very shallow snow depths or no snow on the ground. Region-level (2-digit HUC) snow water equivalent values (percent of median) are as follows: Pacific Northwest 55%, Missouri 56%, Upper Colorado 24%, Great Basin 18%, Lower Colorado 14%, Rio Grande 8%, and Arkansas-White-Red 8%.

In California, statewide snowpack is 18% of normal (April 1), with the Southern Sierra at 32%, Central Sierra at 21%, and Northern Sierra at 6%. Despite poor snowpack conditions, California’s reservoirs remain at or above historical averages for the date (March 31), with Lake Shasta and Lake Oroville at 113% and 123% of average, respectively.

In the Southwest, the U.S. Bureau of Reclamation (March 29) reports critically low levels at Lake Powell (24% full; 41% of average for the date) and Lake Mead (33% full; 52% of average for the date), with the total Colorado River system at 36% of capacity (compared to 41% at the same time last year).

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

On this week’s map, widespread degradations were made in drought-affected areas of Texas, Oklahoma and Arkansas. During the past 30-day period, the National Drought Mitigation Center’s Conditions Monitoring Observer Reports tool showed numerous impact reports across the region.

For the week, dry conditions prevailed across the region. Looking at climatological rankings for the past 90-day period (Dec. 31 to March 31), several locations ranked among their driest on record, including Austin, Texas (fourth driest; -5.53 inches), Brownsville, Texas (driest on record; -3.38 inches), Oklahoma City, Oklahoma (driest on record; -3.61 inches), and Monticello, Arkansas (driest on record; -8.95 inches.

In Texas, Water for Texas (April 1) reports statewide reservoirs at 73.5% full, with eastern reservoirs in good condition while many western and southern reservoirs remain below normal, including Falcon Reservoir (19% full). Average temperatures for the week were above normal across the region (3 to 15+ degrees Fahrenheit) with dry conditions prevailing.

High Plains

Drought expanded and intensified from Oklahoma to South Dakota.

Widespread degradations were centered across Colorado and Wyoming, and to a lesser extent across portions of New Mexico and Montana.

Midwest

Improvements were made across Iowa in response to rainfall during the past week. One-category improvements were observed in areas of moderate drought to severe drought.

Snowpack across the Northern Great Lakes Region continues to decline, with NWS NOHRSC reporting 30.5% snow cover, an average depth of 4.2 inches, and a maximum depth of 64.9 inches. Temperatures were above normal across most of the region, with anomalies ranging from 2 to 15 degrees.

West

Conditions deteriorated significantly on the map in response to the combination of record to near-record heat and very poor snowpack conditions.

The recent heat wave accelerated snowmelt across the region over the past few weeks, with many NRCS SNOTEL stations reporting little to no snow on the ground or unseasonably low levels. Peak runoff is occurring earlier than normal—or has already passed in some locations—raising concerns about reduced inflows into reservoirs moving through spring and into the summer months.

In the Upper Colorado River Basin, Lake Powell is 25% full, while upstream reservoirs show mixed conditions, including Flaming Gorge (82% full), Blue Mesa (50%), and Navajo Lake (62%). In Rio Grande Basin in New Mexico, Elephant Butte is 12% full and Caballo Reservoir is 7% full.

Looking ahead

The National Weather Service’s Weather Prediction Center 7-Day Quantitative Precipitation Forecast (QPF, liquid equivalent) calls for precipitation accumulations generally ranging from 2 to 4 inches across eastern portions of the Southern Plains and Midwest. The heaviest totals along a corridor from eastern Texas through the lower Mississippi Valley into portions of the upper Mississippi Valley.

Across the High Plains, light-to-moderate liquid precipitation accumulations ranging from 0.5 to 2 inches are expected, with the greatest totals across portions of the Dakotas. In the West, light-to-moderate liquid precipitation accumulations are expected across the western areas of the region. In the higher elevations, snow is expected across portions of the central and northern Rockies.

Dry conditions are expected to prevail across much of the Southwest, including areas of  New Mexico.

The 6– to 10-day temperature outlook (valid April 7 to 11) calls for above-normal temperatures across much of the western U.S., Southern Plains, and areas of the South. Below-normal temperatures are favored across the Northern Plains.

Near-normal temperatures are expected across portions of Texas. In terms of precipitation, the 6–10-day outlook calls for above-normal precipitation across areas of the eastern half of the western U.S., Plains states, South, and much of the Midwest. Near-normal precipitation is expected across areas outside of these regions, including portions of the western U.S.

David Simeral is with the Western Regional Climate Center.