Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for August 2016 and August-October 2016, various short- and medium-range forecasts and models such as the forecast 5-day and 7-day precipitation totals from the Weather Prediction Center (WPC), the 6-10 day, 8-14 day, and weeks 3-4 CPC forecasts, the NAEFS precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil Moisture (CAS), dynamical models (CFSv2, NMME, IMME, IRI, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer drought termination and amelioration probabilities, August-October climatology, the July-September 2016 (most recently available) Caribbean Regional Climate Center (Caricof) Climate Outlooks (for Puerto Rico), and initial conditions (July 18 Drought Monitor). The transition from El Nino to ENSO neutral occurred in early June, with about a 55% to 60% chance of La Nina conditions during autumn and winter.

Conditions have deteriorated across the Northeast and eastern Great Lakes region over the last four weeks, and conditions are expected to persist through October. No net drought development is expected between mid-July and the end of October, but conditions could expand some and locally deteriorate over the next month or so before some degree of improvement comes during autumn. Short-term deterioration is most likely in the eastern Great Lakes region, where odds favor below-normal precipitation during August, according to the CPC Monthly Outlook. The central Appalachians and upper Ohio Valley, where short-term conditions have been particularly dry, may also see drought develop and intensify into August; however, the seasonal decline in temperature and surface moisture depletion through evaporation and water usage should bring at least limited relief late in the period. It is likely that drought conditions will change by the end of October, but given all forecast considerations, confidence is too low to forecast expansion into any specific area. On the other hand, there are no strong indicators pointing toward improvement by the end of October where drought currently exists, so persistence is generally anticipated.
Forecast confidence for the Northeast and eastern Great Lakes region is moderate.

In the Southeast, significant rains should fall on at least parts of the drought region into early August, possibly bringing limited improvement in the short-term; however, the CPC Seasonal Outlook favors below-normal precipitation across the region during August-October. In addition, the climatological decline in evaporative and usage water loss will occur later and less markedly than in the drought areas farther north. As a result, drought should remain intact where it exists, and expand to cover adjacent areas where some abnormal short-term dryness exists and there are enhanced chances for a dry August-October.
Forecast confidence for the Southeast is moderate.

The isolated patches of drought from southern Iowa and Nebraska southward through Texas are forecast to persist through October, with some expansion likely from the Del Rio/Laredo, TX area northward through the Texas Hill Country. Chances for significant rains increase in late July and early August from central Texas northward. Thereafter, the August-October seasonal outlook favors neither abnormally wet nor abnormally dry weather on the whole. Late July and early August rains would be at least somewhat beneficial if they materialize, but excessive amounts that would relieve drought for the duration of the forecast period are unlikely. The rate of surface moisture loss through evaporation and similar processes should decline toward fall, at least in central and northern parts of the region, but climatological precipitation totals also decline during this period. As a result, no compelling reason exists to expect improvement in any existing areas of drought, but neither is there any confidence in drought developing and persisting in any given region outside the parts of Texas where (a) July was particularly dry, and (b) temperatures do not drop as much climatologically as in some areas farther north.
Forecast confidence for the central and southern Plains is low.

Drought has intensified quickly in the western Dakotas and adjacent Wyoming in recent weeks, and while conditions may deteriorate in late July, across the Black Hills and adjacent areas, longer-term outlooks from late July onward favor above-normal precipitation, including the August-October seasonal outlook. Drought improvement or removal is forecast given the preponderance of forecasts pointing in that direction.
Forecast confidence for the northern Plains is high.

In the areas of the Southwest affected by the seasonal monsoon, soil moisture climatologically increases during August-October with the increased rainfall, particularly early in the period. With outlooks valid from late July through the month of August favoring above-normal rainfall during this climatologically wet season, improvement seems likely. However, it is possible that even a wet monsoon may not be sufficient to bring substantial relief to the multi-year moisture budget shortages affecting the region.
Forecast confidence for the Southwest is moderate.

Across northern sections of the Rockies and Intermountain West, drought persistence is likely, expanding into northern Idaho and adjacent areas of Washington and Montana by the end of October. Prospects for significant precipitation through early August are minimal, and odds favor below-normal precipitation for both August and August-October in all but the easternmost areas of drought. Even there, the lack of short-term precipitation chances plus the seasonal precipitation decline in autumn argues for persistence. Early snow melt loss combined with seasonally dry weather will likely engender drought development in the northern Intermountain West reliant primarily on snowmelt as a source of water. Streamflows are already substantially below normal and should decline further as this relatively dry time of year progresses.
Forecast confidence for the northern Rockies and Intermountain West is high.

In the Far West, August-October is still a dry time of year, although precipitation can increase late in the period across northwestern reaches of the region. Still, the prospect for significant drought-improving precipitation is small through the end of the period. Persistence is forecast primarily due to climatological considerations.
Forecast confidence in the Far West is High.

During August-October, above-normal precipitation is expected on windward parts of the Hawaiian Islands, but there are enhanced chances for drier than normal conditions in leeward areas. As a result, drought should ease in far southern sections of the Big Island, but persist where it exists elsewhere, which are all leeward locations.
Forecast confidence in Hawaii is moderate.

Drought should be removed from southeastern Puerto Rico by the end of October. This area has been dwindling for some time and enough rain is expected during this period to finally eradicate drought from the commonwealth. This is especially true if La Nina conditions develop as they favor wet weather during autumn here.
Forecast confidence in Puerto Rico is moderate.

Forecaster: Richard Tinker

Next Seasonal Drought Outlook issued: August 18, 2016 at 8:30 AM EDT