Regions Of Drought AND Wet Soil Moisture Across the U.S.

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Profound drought continues across the western and north-central portion of the U.S. Rainfall deficits are routinely 9-12 inches and sometimes >15 inches sprawled across the western states to the Dakotas and Minnesota. The 2-week trend indicates the rainfall shortages are steady except increasing in the Columbia Basin and the Upper Midwest particularly Minnesota into northern Iowa.

Highlight: U.S. soil moisture update.

Fig. 1: Rainfall required to neutralize dry Palmer Drought Severity Index (PDSI) and trend from 2 weeks ago.

Fig. 2: The influence on thermal climate by regional anomalous soil moisture conditions.

Discussion: Profound drought continues across the western and north-central portion of the U.S. Rainfall deficits are routinely 9-12 inches and sometimes >15 inches sprawled across the western states to the Dakotas and Minnesota (Fig. 1). The 2-week trend indicates the rainfall shortages are steady except increasing in the Columbia Basin and the Upper Midwest particularly Minnesota into northern Iowa. However, a wetter trend during the past 2 weeks is indicated for much of the Mid-south/East-central U.S. to Texas plus the Atlantic States.

Large regions of anomalous soil moisture (Fig. 2) are excellent predictors of extreme temperature risk whereas drought zones are well-correlated to extreme heat as observed on many occasions across the western states so far this summer season. Large areas of wet soils have a tendency to suppress heat risk as observed in the Mid-south States.

Right now, the soil moisture trend is generally wetter in the South to the Midwest U.S. suggesting lowering anomalous heat risk for mid-to-late summer while strengthening drought supports increased heat risk for the North-central/Upper Midwest States going forward into August. A wet western monsoon regime could suppress heat risk in the West (temporarily).