United States: Pockets of Surplus expected in SW States

24 February 2023

THE BIG PICTURE
The 12-month forecast ending in October 2023 indicates anomalies of varying intensity across several western and southeastern states.

Severe to extreme deficits are expected in the following areas:

West-central Washington into central Oregon, along the Cascade Range.
Central Idaho, near the Salmon River Mountains.
East-central North Dakota, north of the James River.
Northern Florida, in places between the Suwandee and Saint Johns River.
Western regions of the Oklahoma Panhandle.
Northwestern Montana, northwest of the Missouri River.
Western and central Puerto Rico.

Moderate deficits are anticipated in:

Northwestern and southern Wisconsin, which resume further south in northern Iowa.
Northeastern Alaska, north of the Yukon Flats.

Areas experiencing severe to exceptional surpluses include:

Western New Mexico, near the Gila River.
Central Utah, south of the Great Salt Lake.
Northeastern Nevada, along the Humboldt River, moving east to the city of Eureka.
Central California, throughout the Central Valley and central regions of the Sierra Nevada.
Central Montana, near Canyon Ferry Lake.
Southwestern and southeastern Alaska, in regions south of the Iliamna Lake Outlet and along coastal areas of the Aleutian Islands. West-central areas of the Seward Peninsula can expect surpluses of similar intensity.

FORECAST BREAKDOWN
The forecast through April 2023 indicates severe to extreme surpluses to continue throughout western states of the Continental U.S., including central Nevada, central California, southeastern Idaho, and western Colorado. Similar surpluses are expected to continue in pockets across the Rockies. Moderate surpluses are expected to occur in New Hampshire, southern Michigan, and throughout New York. Deficits in west-central Michigan and northern Florida are expected to persist and intensify into exceptional severity, with a combination of exceptional deficit and transitional conditions across the shared border of eastern North Dakota and western Michigan.

Outside of the Continental U.S., widespread extreme to exceptional surpluses are expected to continue throughout Alaska, with the most intense anomalies occurring across the state’s southern regions. In Hawaii, surpluses of similar intensity are also expected to continue. Western Puerto Rico can expect deficits to linger but lessen in severity.

From May through July 2023, surplus anomalies in the eastern states will continue for eastern Nevada, Utah, southern Idaho, and southwestern New Mexico. Southeastern California and northern Florida can expect mild to moderate deficits. Outside of the Continental U.S., Hawaii and the majority of Alaska can expect intense surpluses, except for northwestern Alaska, which can anticipate moderate to severe deficits.

The forecast for the final months – August through October 2023 – predicts that surpluses in Nevada, Utah, Idaho, and New Mexico will endure, with moderate to severe deficits appearing in central Michigan.

IMPACTS
Earlier in February, the Nevada Division of Insurance urged citizens to purchase flood insurance due to changing weather patterns and consistent increases in severe weather throughout the state. Over the summer, Las Vegas experienced continuous heavy rainfall, causing homes, businesses, and parking garages in the city to flood. Liz Martins, public information officer for the Division of Insurance stated that these weather changes “simply can no longer be ignored and should be taken into consideration when evaluating your property’s flood risk.” After studying flood patterns in the southwestern United States, Dr. Guo Yu, a hydrologist at the Desert Research Institute, similarly explained that the frequency of winter storms is anticipated to increase in the coming years, which will increase flooding that occurs during the colder months.

Snowpack in Idaho is reported to be at or above normal levels across nearly the entire state, and is expected to help replenish the region’s water supplies after a persistent drought. In 2021, hot and dry weather caused the amount of runoff from snowpack to be less than normal, causing farmers to irrigate more and pull water from reservoirs earlier than usual. In 2022, runoff was over a million acre feet, filling the area’s reservoirs by June, though previous months were recorded as some of the area’s driest on record. Though this season’s snowpack is promising, Erin Whorton, a hydrologist with the National Resources Conservation Service, stated that “drier soils could be impacting our snowpack runoff efficiency” in the coming spring.

Although California has experienced record-breaking rain and snow this winter, drought remains widespread throughout the state. The United States Drought Monitor shows the majority of California still experiencing "moderate drought," and in some places "severe drought." This is still an improvement from January, as much of the state was in "severe drought" with 7 percent of California in what was considered "exceptional drought" conditions. California is entering three years of its driest conditions, the longest amount of drought since records began. Roger Bales, a professor at UC Merced who specializes in water and climate research, expects that it will take two years of persisting rainfall to replenish California, and a decade or more to refresh the Colorado River Basin, which seven states rely on for water, as well as Mexico.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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