April - June 2008

Latest Seasonal Assessment - Although exceptional drought has been eliminated for most of the Southeast, 12-month precipitation deficits exceed 12 inches across northern parts of Alabama and Georgia. The forecast indicates continued drought improvement across the Southeast, with the odds lowest in the coastal Plain of the Carolinas due to a drier April forecast. Drought should persist or expand slightly across the Florida peninsula, but expected rainfall during the next week could offset a dry April forecast. Small areas of moderate drought in the eastern Dakotas and Minnesota should experience relief. Some improvement is forecast for the northern high Plains, but drought relief is not expected across central Montana. Drought persistence or development is forecast for the central and southern high Plains, west Texas, and much of New Mexico. Although the April – June seasonal forecast indicates below normal precipitation for parts of Nevada and Utah, spring snow melt should boost water supplies and result in improvement across the northern Great Basin. Persistence is forecast in southern Nevada, southern California, and southwest Arizona due to a dry climatology.

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for April - June 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.

During the winter, the widespread area of exceptional drought was eliminated across most of Alabama, Georgia, Tennessee, and the Carolinas. However, 12-month precipitation deficits remain above 12 inches across northern Alabama, northern Georgia, and the piedmont of the Carolinas. Lake Lanier, north of Atlanta, reached a record low on December 28, 2007 and the winter-spring recharge thus far has been below normal. Although improvment or some improvement is forecast for the southeast, long-term hydrological impacts will likely continue into the summer when water demands increase. Alabama and Tennessee will most likely experience improvement. Monthly precipitation forecasts indicate lower odds for improvement across the coastal Plain of the Carolinas. Drought persistence or development is expected across parts of the Florida peninsula which will increase the wildfire risk. In the southern Florida peninsula, rainfall during the remainder of March could offset the dry April forecast.

Across the eastern Dakotas and Minnesota, improvement for the two small areas of moderate drought is expected. Climatology with the start of the summer thunderstorm season favors some improvement across the western Dakotas. 3-month soil moisture and runoff predictors support persistence across central Montana. The western Corn Belt is susceptible to dryness during La Niña springs and the CFS seasonal precipitation forecast indicates below normal precipitation from Nebraska into western Iowa. Development is expected in the central high Plains where abnormal dryness currently exists. Despite precipitation earlier this week, development is forecast to spread east across southern Nebraska and northern Kansas.

A sharp gradient between drier-than-normal and wetter-than-normal conditions currently exists across central Texas. From March 17-18, rainfall totals exceeded 2 inches across northwest Texas. Despite the beneficial rainfall this week, seasonal precipitation tools including the official CPC outlook favor a widespread area of persistence or development across the western half of Texas and much of New Mexico. More than 100 counties in west Texas are under burn bans and the expected dryness will likely maintain a high wildfire risk during the spring.

Since December, a series of winter storms have resulted in drought improvement across the west, especially in the central Rockies. However, drought associated with hydrological impacts persists. Snow-water equivalent values are at or above normal in southern Idaho, northern Utah, and parts of Nevada. Despite below normal precipitation in the CPC seasonal outlook, the combination of the upcoming spring snow melt and a few more expected storms in the short to medium range should bring improvement to much of the northern Great Basin. Farther south, in southern California, southern Nevada, and southwest Arizona, persistence is likely due to climatology.

In Hawaii, abnormal dryness currently exists. Development is not forecast through June, but longer range forecasts suggest that development could occur later in the summer.