Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for September through November 2016 (SON), various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), dynamical models (CFSv2, NMME, IRI, IMME, and ECMWF), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer drought termination and amelioration probabilities, climatology for the SON season, and initial conditions.

Inadequate rainfall and above-average temperatures (1 to 3 degrees F above-normal) resulted in drought expansion and intensification across parts of the Northeast along with Ohio, northeast Indiana, and lower Michigan this summer. The Advanced Hydrologic Prediction Service (AHPS) indicates that 180-day precipitation deficits are locally more than 8 inches across parts of the Northeast. As examples, the precipitation deficit is nearly 8 inches at both Boston and Buffalo since January 1. Due to these long term precipitation deficits and without a wet signal among the precipitation tools, persistence is most likely for the ongoing drought areas of New England along with parts of New York and Pennsylvania. By the end of November, drought is more likely to be removed (in current areas of D1) across northern Ohio, northeast Indiana, and lower Michigan due to the shorter duration of the drought in these areas. Short-term drought development remains a concern during the next month across the upper Ohio Valley. It should be noted that as temperatures cool this fall and evapotranspiration rates decrease, drought expansion and further intensification of drought across the Northeast becomes less likely. Forecast confidence is low across the Northeast due to varying factors such as the decreasing evapotranspiration rates, weak signals among precipitation tools, and the long-term precipitation deficits.

Forecast confidence is low for the Northeast and moderate across Ohio, northeast Indiana, and lower Michigan.

Abnormal heat (temperatures averaging 1 to 3 degrees F above-normal) coupled with insufficient rainfall this summer also led to drought development and intensification across the Southeast. Soil moisture ranks in the lowest 10th percentile across much of the northern third of Georgia, prompting the U.S. Drought Monitor (USDM) to designate this area with D2 (severe) to D3 (extreme) drought. The CPC seasonal outlook for SON favors below-median precipitation for the interior Southeast. Given the continued worsening of drought, a dry signal in the seasonal precipitation tools, and a relatively dry climatology (15 to 20 percent of annual precipitation occurs during SON), drought persistence and development is forecast for parts of Alabama, Georgia, Tennessee, and the western Carolinas.

During early to mid-August, an upper-level low tracked west along the Gulf Coast and resulted in major flooding across Louisiana. The heaviest rainfall associated with this upper-level low missed most of the ongoing drought areas of northeast Mississippi. The enhanced odds for below-median precipitation during SON favors persistence for the ongoing drought across Mississippi, but additional development is not expected due to rainfall forecast during the next two weeks.

Forecast confidence for the Southeast is moderate.

Small areas of moderate to severe drought are currently depicted on the U.S. Drought Monitor across parts of Oklahoma, Texas, and southeast New Mexico. A forecast for improvement and removal of these drought areas is mostly based on rainfall expected during the remainder of August. The WPC indicates a broad area of more than 3 inches of rainfall, from southeast Oklahoma extending to the middle Rio Grande Valley, during the next week. The GFS model favors a continuation of above-median rainfall during the Week-2 period. Due to the increased rainfall and cloud cover forecasted, below-normal temperatures are also favored during the remainder of August. 

Forecast confidence for the southern Great Plains is moderate.

Parts of the northern and central Great Plains are currently designated with moderate (D1) to extreme (D3) drought, with the most widespread drought centered across the northern high Plains. An amplifying upper-level trough is expected to bring 0.5 to 2.0 inches of rainfall during the next few days to most these drought areas. The CPC seasonal precipitation outlook features a tilt in the odds for above-median precipitation across the northern Great Plains. Based this seasonal precipitation outlook and short-term rainfall, improvement or removal is forecast. However, forecast confidence is tempered since the next three months are an increasingly dry time of year.
 
Forecast confidence for the northern and central Great Plains is low.

Although the AHPS indicates that most of southeast Arizona and western New Mexico received above-normal rainfall during the past 30 days, only minor improvements were made to the USDM depiction. Rainfall expected during the next week along with a relatively wet climatology through September favors improvement or removal of drought across southeast Arizona and western New Mexico. However, forecast confidence is low considering that monsoon rainfall in these areas is typically convective and scattered.
 
Forecast confidence for southeast Arizona and western New Mexico is low.

During the past month, drought coverage and intensity remained nearly steady across the West with development or intensification limited to parts of the Great Basin, northern Rockies, and eastern Oregon. Outside of the wetter monsoon areas of Arizona and New Mexico, persistence is most likely throughout most of the West given the long-term duration of the drought and the drier climatology through October. Removal is forecast for the small drought area along coastal Oregon as this area typically becomes wetter earlier in the fall season.

Forecast confidence is high for California and moderate for the remainder of the West.

During the past El Nino, drought coverage peaked at nearly 80 percent of the Hawaiian Islands in early April. Since that time, that coverage decreased and is currently less than 15 percent. The enhanced odds for above-median precipitation forecast during SON favors continued removal of drought.

Forecast confidence for Hawaii is moderate.

Only a small area of moderate drought (less than 7 percent coverage) persists across Puerto Rico. Based on a relatively wet climatology and the potential for La Nina conditions to develop, removal of this drought area is likely.

Forecast confidence for Puerto Rico is high.

Forecaster: Brad Pugh

Next Seasonal Drought Outlook issued: September 15, 2016 at 8:30 AM EDT