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07/09/2018, 7:26 pm EDT

U.S. Soil Moisture Outlook

Highlight:  Sneaky dry Iowa in August; Northeast continues to dry out Discussion: Much of the U.S. has drier-than-normal soil moisture (Fig. 1) with substantial rainfall needed to neutralize negative Palmer Drought Severity Index (PDSI) values. The strongest soil moisture deficits are across the northern Rocky Mountains, Washington Cascades, northern Arizona, central and northern Texas and parts of the east-central Great Plains.  So far in July the soil moisture trend is drier from the eastern Corn Belt to New England and the Mid-Atlantic States and northwest Great Plains while the wet trend is confined to the Upper Midwest to central/southwest Kansas and the northwest/north Gulf Coast. The NCEP CFS V2 soil moisture projection for the U.S. for August (Fig. 2) indicates intensification of the drought in the northwest Gulf of Mexico States defeating the idea of any tropical cyclone activity the next 4-8 weeks. Dryness persists in the Northeast to an already dry zone foreshadowing an already forecast warmer-than-normal climate for late summer. The north/west growing areas trend wetter but watch out in Iowa where late summer dryness sneaks up on corn. The Southeast and Interior Southwest/West U.S. trend wetter. The Southeast U.S. wet trend could be related to a tropical event in August. Summary: A contributor to the early summer near record heat is a large area of soil moisture deficit across the U.S. Departing the peak of summer should open the door for some beneficial rainfall easing drought Interior West U.S. with some of that moisture extending northeastward to the Upper Midwest. The Southeast is wetter possibly due to a tropical event. Meanwhile the Texas drought shifts eastward and Northeast U.S. drought persists. Fig. 1: Rainfall needed to erase soil moisture deficit and July trend so far. Fig. 2: U.S. soil moisture forecast through August using the NCEP CFS V2 model.