Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for December 2017 through February 2018 (DJF 2017-18), 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), Weeks 3-4, dynamical models at the seasonal time scale, 384-hour total precipitation forecasts from several runs of the GFS, 240-hour total precipitation forecasts from the ECMWF, climatology for the DJF season including median soil moisture changes, and initial conditions (the U.S. Drought Monitor valid on November 14, 2017). La Nina conditions are predicted to continue (~65-75% chance) at least through boreal winter 2017-18.

Across the Northeast during the past 30-days, the Departure from Normal Precipitation (DNP) map depicts wetter-than-normal conditions across approximately the western and eastern thirds of this region, with intervening near- to drier-than-normal conditions for the central third. A few areas, such as near and along the New Hampshire-Maine border, and northern New York's Tug Hill Plateau area, report precipitation surpluses of at least 4 inches during the past 30 days. Looking back over the past 121 years of record, the Northeast typically receives 20-30 percent of its annual precipitation during this three-month period. Though there are a few widely scattered areas of abnormal dryness (D0) on the U.S. Drought Monitor in the Northeast, there is no drought at this time. It is unlikely that drought will redevelop across this region during the winter.

Confidence for the Northeast is moderate to high.

Thirty-day precipitation anomalies in the Southeast indicate mostly below- to near-normal precipitation, with the exception of far western sections of Virginia and the Carolinas, and over southern Florida, where above-normal precipitation fell. Typically during the DJF season, most of this region receives 20-30 percent of its annual precipitation. The exception is the Florida Peninsula, where the historical record reveals a gradation of values ranging from 15-20 percent in the north to 5-10 percent in the south. Existing moderate drought (D1) from the Carolina Piedmont region into southern Virginia (and over a localized area along the southern border of Alabama/Georgia) is expected to persist and/or intensify during the DJF period, as precipitation predictions at nearly all time-scales out to one season in advance support below normal precipitation. Drought development is also anticipated across portions of the Southeast region. This is a common (though not guaranteed) occurrence during La Nina winters. Across most of peninsular Florida, drought development is considered much less likely, as it received copious rainfall from both Hurricane Irma earlier in the season and from a record wet season this year.

Confidence for the Southeast is moderate to high.

Across the South, most areas report precipitation deficits during the past 30-days, topping out with 3-5 inch deficits most notably in the Lower Mississippi Valley. In contrast, surpluses of 1-4 inches were reported in Tennessee and south-central Louisiana. For Oklahoma and all but eastern Texas, the 121-year climatological record indicates only 5-20 percent of the annual precipitation amounts can be expected during the DJF season, with the lowest amounts over the typically drier southern High Plains. For the remainder of the South (Arkansas, Louisiana, Mississippi, and Tennessee), 20-30 percent of their annual precipitation can normally be anticipated during DJF. Dryness and drought (D0 to D2) has expanded in coverage during the past month across this region. According to WPC's Week 1 precipitation forecast, precipitation amounts are expected to be light (less than 0.5-inch) over most of this region. Beyond that period, precipitation outlooks generally call for below-normal precipitation over this area. As with the Southeast, drought is likely to persist and/or intensify, as well as develop in other portions of the South, during DJF.

Confidence for the South is moderate to high.

Thirty-day DNPs across the Midwest depict near- to below-normal precipitation over approximately the western half of the Midwest region, and near- to above-normal precipitation over the eastern half. Precipitation deficits generally ranged from 1-3 inches, while surpluses ranged from 1-5 inches or more. The largest surpluses were noted over areas downwind of Lakes Superior and Huron, where the lake-effect snow season has started. The DJF season is typically a drier time of year across the Midwestern states, with climatology indicating only 5-20 percent of the area's annual precipitation can be expected. Dryness and drought (D0 to D2) has been focused primarily in eastern and southern Missouri, and in south-central Iowa. For Week-1, WPC predicts 0.5-2 inches of precipitation for approximately the eastern half of the region, and less than 0.5-inch elsewhere. Week-2 and experimental Week 3-4 precipitation outlooks favor near to below-normal precipitation. CPC's official 30-day and 90-day precipitation outlooks indicate a return to above-normal precipitation amounts over much of the Midwest region, especially northern and eastern sections. It is over these northern and eastern sections that prospects for drought improvement and/or removal are greatest. Areas to the southwest are considered more likely to experience drought persistence and/or intensification.

Confidence for the Midwest is low to moderate.

Precipitation deficits ranged from near zero to 2 inches during the past 30-days over most of the High Plains region. On the other hand, precipitation surpluses of 0.5-2 inches (locally greater) were noted over central parts of Montana. Looked at another way, the 30-day Percent of Normal Precipitation (PNP) map depicts much of eastern Colorado, western Kansas, southern and eastern Nebraska, and portions of the Dakotas, as receiving only 5-25 percent of its normal precipitation during the 30-day period, and central Montana receiving 110-300 percent of normal (locally greater) during the period.  As with the Midwest region, this is also a drier time of year for the High Plains region, with the climatological record indicating the reception of only 5-20 percent of the region's annual precipitation during winter (DJF). CPC's 30-day and 90-day precipitation outlooks favor above- normal precipitation amounts across nearly all of the large, ongoing drought area in the region. While western Montana may get some relief from the drought this winter (primarily from the expected proximity of the polar jetstream and associated storm track associated with La Nina), substantial relief appears less likely for eastern Montana and the Dakotas which have larger deficits to overcome.

Confidence for the High Plains is moderate.

The 30-day PNPs over the Pacific Northwest, the northern half of the Intermountain region (excluding eastern Idaho), and the northern Rockies show values ranging from 75-200 percent of normal (25-75 percent of normal in eastern Idaho). Historically, 20-50 percent of the region's annual precipitation is received during DJF, with the Oregon coast receiving nearly one-half of its annual precipitation during this time. For approximately the southern half of the West, with the exception of northern California and far northern Nevada, 30-day PNPs were in the lowest 25 percent. PNPs for far northern Nevada ranged from 25-75 percent of normal, while across northern California PNPs ranged from 25 to 200 percent. The percentage of annual precipitation that can be expected during DJF ranges from 20 to almost 70 percent, with the highest percentages, by far, in northern, central, and coastal southern California (50-67 percent of normal). Snow water content ranges from 100-200 percent of average or more in the Pacific Northwest, the northern half of the Intermountain Region, the northern Rockies, and far northern Nevada. For approximately the southern half of the West, snow water content is at or below 75 percent of average, and thus off to a slow start for this new Water Year. The precipitation forecast for the area of moderate drought (D1) currently over northeastern Washington State is uncertain. Though it is a common occurrence during La Nina winters for the polar jet stream and the associated storm track to pass through this region, the uncertainty is rooted in impacts of the complex topography, and that eastern Washington is in the rain shadow of the northern Cascades, and therefore typically receives little in the way of precipitation, especially compared to the mountainous surroundings both west and east of this area. CPC predicts weak tilts towards above-normal precipitation in northeastern Washington State, and this has the modest support of the long-term (121-years) climatological record. Therefore, drought removal is favored in this relatively small area. The seasonal drought outlook for the southern portion of the West is more straightforward, favoring drought persistence and/or intensification, as well as development across the far south. This is based on CPC's monthly and seasonal precipitation outlooks, patterns typically associated with La Nina winters, and, for parts of southern California and Arizona, the expectation of continuing impacts related to the multi-year drought.

Confidence for the (approximate) northern half of the West is low to moderate, and for the southern half of the West, confidence is deemed moderate to high.

The DJF season represents the core of the rainy season across the Hawaiian Islands, and climatology alone favors at least some improvement in drought conditions. Based on a relatively wet seasonal outlook, and a wet climatology, drought improvement/removal is indicated. There is currently no drought in Alaska or Puerto Rico.

Confidence for Hawaii is moderate to high.

Forecaster: Anthony Artusa

Next Seasonal Outlook issued: December 21, 2017 at 8:30 AM EST