Tools used in the Drought Outlook included the official CPC long-lead precipitation outlooks for January 2008 and January - March 2008, various medium and short-range forecasts such as the 5-day, 6- to 10-day, and 8- to 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.
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 2007 precipitation totals around 15 inches below normal were common. Despite recent 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. The forecast for drought development near the central Gulf Coast and the far western Florida Panhandle was scaled back, however, because recent rainfall surpluses make it unlikely that conditions will be dry enough through March 2008 to induce full-fledged drought conditions even though subnormal precipitation is anticipated for this period.
Farther north 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, thus drought improvement is forecast. Farther east, medium-range forecasts support improvement across central sections of Maryland and Virginia.
Meanwhile, between the two aforementioned areas, the forecast for some improvement across the upper South, where La Nina composites and most other tools were non-committal, was expanded to include southeastern Virginia and the lower Delmarva Peninsula, where monthly and seasonal forecasts slightly favor below-normal precipitation.
Across the Great Lakes and Midwest, improvement for the small areas of moderate drought remains likely due to expected wetness in the medium-range forecasts and/or the monthly and seasonal forecasts. However, it should be noted that drier than normal conditions may return to some areas later in the spring, and the western Corn Belt is especially susceptible to dryness during La Nina 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. Farther south, the patches of drought extending from the west-central Plains to southern Texas are expected to persist. From the most recent outlook, drought development was removed from the central High Plains, where heavy precipitation is expected in the medium-range forecasts, but this region will need to be closely monitored because La Nina soil moisture composites favor dryness in this region through early spring. Drought development is forecast for much of central and southern Texas where topsoil moisture is low and La Nina soil moisture composites along with precipitation outlooks on most time scales favor drier than normal conditions.
In the northern half of the West, La Nina favors above normal precipitation for the interior Pacific Northwest and the northern half of the Rockies. 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.
Farther south, La Nina typically brings drier than normal conditions to the southern half of California and the Southwest. However, short- and medium-range forecasts both indicate that a series of storms could bring heavy to excessive precipitation to a large part of California and, to a lesser extent, much of the Great Basin and Desert Southwest. As a result, this forecast is more optimistic than our prior forecast through March 2008, with drought improvement expected in the Sierra Nevada and along the west coast of California, and more limited improvement anticipated in the central California valleys and the Southwest.