Increasing Rainfall Shortages Across U.S.

Fig. 1: Rainfall required to end dry Palmer Drought Severity Index.

Discussion: Soil moisture deficits increase dramatically once meteorological summer arrives due to the intensity of the sun. Only areas receiving moderate to heavy rainfall, cloud cover or cool temperatures can avoid this problem. Right now, significant soil moisture shortages are affecting a vast portion of the lower 48 contiguous states (Fig. 1). Most notably, >15 in. rainfall deficits are affecting parched northern California, parts of the Northwest U.S. and adding the upper Texas Coast. Not far behind with 12-15 in. range deficits include Central California, much of Central and East Texas, and southeastern North Carolina. All of these areas are in drought or will be soon!

Rainfall deficits of 9-12 in. are also potentially hostile for significant or flash drought evolution. Parts of the Interior West, South and Southeast/Mid-Atlantic States have this risk. Rainfall deficits are steadily increasing in the Midwest U.S. and New England.

The only location with very wet to extreme wet soils is parts of Wyoming and the Upper Midwest States.