Nationwide
This U.S. Drought Monitor (USDM) week saw widespread improvement in drought-related conditions on the map across areas of the South, Plains, Midwest, Mid-Atlantic, and the West.
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In the Plains and Midwest, locally heavy rainfall accumulations (up to 7 inches) were observed in drought-affected areas of Oklahoma, Kansas, Nebraska, Missouri, and Iowa, leading to continued improvements of conditions on the ground (vegetation health, soil moisture, surface water) as well as reductions in the longer-term precipitation deficits. Likewise, above-normal precipitation during the past several months led to the removal of areas of drought on the map in Michigan’s Upper Peninsula as well as in southern Wisconsin. In the South, isolated areas of central and west-central Texas saw minor improvements in response to recent rains and improving conditions during the past 30-day period. In the Mid-Atlantic, 1-6-inch accumulations were observed in areas of North Carolina and Virginia this week, leading to the removal of areas of Abnormally Dry (D0).
Out West, some minor improvements were logged in central and northern Arizona, where precipitation has been above normal since January 1. In southeastern Montana, recent rains erased Water Year (since October 1) deficits and have improved soil moisture conditions and vegetation health. Across the border in the Bighorn Mountains of north-central Wyoming, areas of Moderate Drought (D1) were removed in response to above-normal snowpack conditions observed in its associated drainage basins.
In California, the state’s reservoirs are above normal levels moving into the dry season, with the state’s two largest reservoirs (Lake Shasta and Lake Oroville) at 115% and 126% of their historical average for the date (May 21), respectively. In the Southwest, Lake Powell is currently 33% full (58% of typical storage level for the date) and Lake Mead is 35% full (62% of average), with the total Lower Colorado system at 42% full as of May 20 (compared to 37% full at the same time last year), according to the U.S. Bureau of Reclamation. In Arizona, the Salt River Project reports the Salt River system reservoirs at 95% full, the Verde River system at 70% full, and the total reservoir system at 92% full (compared to 99% full a year ago). In New Mexico, the state’s largest reservoir along the Rio Grande is currently at 23% full (59% of average). In the Pacific Northwest, Washington’s Franklin D. Roosevelt Lake is at 87% full (176% of average for the date).
In terms of degradations on the map this week, the only noteworthy ones were made in areas of South Florida where areas of Moderate Drought (D1) expanded in response to dry conditions during the past 60-day period with reports of various impacts, including burn bans, lake levels dropping at Lake Okeechobee, reduced soil moisture, and some minor impact in the recreation sector due to low surface water levels. Overall, looking at the broader drought situation across the conterminous U.S., the total percentage of drought coverage is at its lowest since 2020.
The West
Out West, some minor improvements were made on the map in central and northern Arizona, eastern New Mexico, southern Colorado, southern Nevada, north-central Wyoming, and southeastern and central Montana.
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Looking at precipitation across the region, the start of the Water Year was not looking good with most of the region experiencing below-normal precipitation levels. However, the period from January 1 to current (May 21) was much more promising, with above-normal precipitation observed across much of the region, with the exception of areas of the Pacific Northwest including Washington, northern Idaho, and western and central Montana, as well as areas of the Southwest (eastern New Mexico and northwestern Arizona).
In terms of snowpack, the Natural Resources Conservation Service Snow Telemetry (SNOTEL) network is reporting (May 21) the following region-level (2-digit HUC) snow water equivalent levels (percent of 1991-2020 median): Pacific Northwest 73%, Missouri 100%, California 147%, Great Basin 137%, Upper Colorado 112%, Arkansas-White-Red 140%, Lower Colorado 232%, and Rio Grande 52%.
For the week, conditions were very dry across the region except for some isolated, light shower activity in eastern portions of New Mexico, Colorado, Wyoming, and Montana.
The High Plains
On this week’s map, Kansas, Nebraska, North Dakota, and the eastern Plains of Montana saw improvements in drought-affected areas.
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In Kansas and Nebraska, moderate to heavy rainfall accumulations (2 to 7+ inches) led to a reduction in areas of drought and provided a boost in soil moisture and streamflow levels. In North Dakota, areas of Moderate Drought (D1) were reduced in response to above-normal precipitation during the past 30-to-90-day period, as well as numerous recent field reports coming into the National Drought Mitigation Center’s Condition Monitoring Observer Reports system.
In terms of NOAA National Centers for Environmental Information (NCEI) regional climatological rankings, the Great Plains Region observed its 44th wettest (near normal) and 12th warmest (+3.9 F anomaly) January-April period on record.
The South
Across portions of the region, the active pattern continued with significant rainfall accumulations observed in portions of eastern Texas, southern Louisiana, and southern Mississippi, where 7-day totals ranged from 2 to 8 inches.
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Moreover, beneficial rainfall continued to help ease drought-related conditions in areas of Texas and Oklahoma. On the map, isolated rainfall activity this week led to some minor improvements in north-central Oklahoma, while areas of central and west-central Texas saw minor improvements. According to Water for Texas (May 22), statewide reservoirs are currently at 77.3% full, with numerous reservoirs in the eastern part of the state near capacity, while many reservoirs in the western half of the state are experiencing below-normal levels.
Looking at climatological rankings for the January 2024-April 2024 period, the region experienced its 19th wettest (+2.32-inch anomaly) and the 11th warmest (+3.2 F anomaly) on record, according to NOAA NCEI. — UNL Drought Monitor
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