Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for January - March 2008, the four-month drought termination and amelioration probabilities, various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the soil moisture tools based on the GFS model and the Constructed Analogue on Soil moisture, the CFS seasonal precipitation forecasts, and La Niña composites of soil moisture.
Across the southeast, Gulf Coast, and Florida, this outlook made little change to the previous outlook. Drought persistence or development should be widespread with La Nina conditions typically bringing subnormal precipitation to the region during the forecast time period. Exceptional drought continues for parts of Alabama, Georgia, and the Carolinas where year-to-date precipitation deficits around 15 inches are common. Atlanta and Athens, Georgia could record their driest years (January – December). Despite short-term rainfall, all tools in the long range strongly indicate below normal precipitation and drought continuing. Across the Florida peninsula, drought development is anticipated and the expected dryness will increase the likelihood for an active wildfire season during the spring.
Farther inland across eastern parts of Kentucky and Tennessee, near or above normal precipitation typically occurs during La Nina winters, and medium-range and long-range forecast models remain consistent with this scenario. Also, soil moisture composites indicate an increased likelihood for improvement. Therefore, odds are for improvement for northern Tennessee into eastern Kentucky. Medium-range forecasts support further improvement in the drought still affecting central Virginia and the lower Delmarva.
Across the Great Lakes and Midwest, improvement for the small areas of moderate drought remains likely due to expected wetness either in the medium-range forecasts or in the monthly and seasonal forecasts. Drought will likely be eliminated but drier than normal conditions may return later in the spring. The western Corn Belt is especially susceptible to dryness during La Niña springs. Drought will likely persist across the western Dakotas and western Nebraska as drought relief is usually not seen during the winter due to frozen ground and relatively light precipitation totals.
From the most recent outlook, drought development was scaled back in west Texas where initial conditions are quite wet for this time of year. However, topsoil moisture is low in south Texas. La Niña soil moisture composites along with various seasonal precipitation outlooks favor drought development in south Texas. Farther north, small areas of moderate drought continue across the southern high Plains. La Niña soil moisture composites and the CFS seasonal precipitation forecast indicate that drought will expand across the central and southern high Plains.
In the West, La Niña favors above normal precipitation for the interior Pacific Northwest and northern Rockies, and a series of storms striking the Pacific Coast during the past month brought rain and snow to the drought areas from the interior Northwest to the northern Rockies, and long-range forecasts indicate relief will continue.
Snow-water equivalent values for the Sierra Nevada are currently well below average. During the remainder of December, a wet weather pattern featuring a series of Pacific storms will likely increase snow pack across California. Therefore, some improvement is expected in the near-term. Despite recent wetness in southern California and southwest Arizona, either some improvement or drought persistence is forecast due to seasonal precipitation outlooks favoring below normal precipitation.