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07/31/2018, 1:15 pm EDT

U.S. Soil Moisture Update

Rainfall Needed to End U.S. Drought – Weekly Update/Change Fig. 1: NOAA depiction of rainfall needed in climate divisions to neutralize negative Palmer Drought Severity Index (PDSI). Discussion: Vast areas of soil moisture deficit continue to affect the U.S. and is a lead catalyst for the historic warmer-than-normal summer 2018 (so far). The worst soil moisture deficit is in northeast Georgia (over 15 in.) followed closely by north-central Oregon, northeast Kansas and parts of Louisiana (12-15 in.). Officially, severe (or worse) drought is affecting the Northwest, California, the Southwest and Great Basin plus Texas to the Delta region. Added are parts of the far northern states. D2 (severe drought) or worse drought conditions are affecting 25 of the lower 48 contiguous states as of the end of July. Last week brought drier changes to the coastal Northwest as drought/fire danger is becoming extreme. Southern Arizona drought worsened last week. The “sneaky” dry trend is most notable last week in the Ohio Valley and parts of the North-Central U.S. Dryness in the South is immense and worsening in south-central Texas, central Louisiana, Mississippi and Alabama. Heavy rains doused the previous dry soils of the Northeast Corridor. Fig. 1: The ECM Ensemble 15-day percent of normal rainfall forecast indicates significant drying in the Central and West U.S. The 15-day percent of normal rainfall across the U.S. according to the European ensemble (model) indicates more wet weather in the Southeast U.S. which should ease drought in Alabama and the Carolinas (Fig. 1). There are also indications of wet weather in the drought region of the coastal Northwest U.S.  Dryness prevails elsewhere! Drought conditions in Texas to the Delta region, southern Plains and toward the Corn Belt worsen. Fire danger zones across much of the West worsen especially the Interior Northwest U.S. Summary: Immense dry-to-drought conditions are affecting much of the U.S. as peak-of-summer is passing. Last week drought conditions worsened in the coastal Northwest, Mid-South U.S. to the Ohio Valley. Excessive rains occurred in the East. Over the next 15 days dry-to-drought conditions in the Central and West U.S. will worsen while Southeast drought areas erode.