January - March 2009

Latest Seasonal Assessment - Following significant drought relief across the Southeast during early December, additional improvement is forecast across the upper Ohio Valley and southern Appalachians. In contrast, the moderate drought in Florida should persist and expand across the northern and central peninsula. As the wildfire season approaches, the expected drought development should be closely monitored. Improvement is forecast in southern and eastern Oklahoma, while drought should persist in south-central Texas and may expand during the next three months. Persistence is also forecast for the small drought areas in southeast Colorado and the northern high Plains. During the remainder of December, frequent periods of snowfall can be expected across the Great Lakes region. With long-range forecasts showing mixed signals, some improvement is forecast in southeast Minnesota, Wisconsin, and the upper peninsula of Michigan. The short and medium-range forecasts support a wet, cold pattern across the West. This expected weather pattern should increase mountain snowpack that is critical for hydrological recharge. Although the January – March 2009 outlook is noncommittal regarding precipitation, improvement or some improvement is forecast across California, the Great Basin, and parts of the Rockies. However, it should be noted that improvement may not occur until the spring snow melt begins. Due to a wet climatology, improvement should continue across the Hawaiian Islands.

Tools used in the Drought Outlook included the official CPC precipitation outlook for January 2009 and January – March 2009, various short and medium-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 (CAS) moisture, the CFS seasonal precipitation forecast, and climatology.

During the past week, substantial drought relief has occurred across the upper southern Appalachians and drought was eliminated in Alabama. The watershed of Georgia’s Lake Lanier received 2 to 4 inches of rainfall, resulting in a one foot rise of the lake’s level since December 9. Across the upper Ohio Valley, additional moderate to heavy rainfall amounts can be expected in the short-term. The 6-10/8-14 day outlooks also call for above normal precipitation. Seasonal precipitation tools indicate that drought improvement should continue during the remainder of the winter, especially in southern Ohio, Kentucky, and eastern Tennessee. Odds for improvement decrease slightly farther south in northeast Georgia and the upstate of South Carolina, but climatology favors continued improvement. However, the protracted hydrological drought may linger into the spring.
Confidence for the upper Ohio Valley: High
Confidence for the southern Appalachians: Moderate

In Florida, climatology along with forecast tools at all time ranges indicates expansion of drought across the northern and central peninsula. If drought development occurs, an increase in wildfire activity would likely occur during the spring.
Confidence for Florida: High

In the Great Lakes region, short and medium-range forecasts are fairly wet while the seasonal tools are noncommittal. The outlook calls for some improvement due to the lack of a signal during the January – March 2009 period. The most likely area for improvement is the southern extent of drought in Wisconsin.
Confidence for Great Lakes region: Moderate

In southern and eastern Oklahoma, the January – March 2009 seasonal outlook calls for above normal precipitation. Also, precipitation normals increase during March across southeast Oklahoma. Therefore, the outlook indicates improvement.
Confidence for southern and eastern Oklahoma: Moderate

In Texas, drought should persist in south-central areas and may expand to the south towards the lower Rio Grande. Climatology is quite dry for this time of year, especially across the western half of the ongoing drought area. The January – March 2009 seasonal outlook calls for a tilt in the odds towards below normal precipitation across western and southern Texas. Drought development is forecast for areas of western Texas that are currently experiencing abnormal dryness.
Confidence for Texas: High in western areas; moderate in eastern areas

Across the widespread drought area covering California, the Great Basin, and parts of the Rockies, changes to the present drought status vary with location and may not be realized until the spring snow melt occurs. A poor start to the wet season has resulted in low snow-water content values across this region. However, during the remainder of December and perhaps into the beginning of the New Year, a persistent trough should result in above normal precipitation and below normal temperatures. This expected weather pattern should increase snowpack, a critical source of water for the region. The highest precipitation amounts in the short and medium range are expected in California with lower amounts across northern Nevada and southern Idaho where some improvement is forecast. With a few seasonal tools favoring a return of dryness, forecast confidence in the improvement and some improvement is tempered. Although the January – March 2009 seasonal outlook calls for equal chances for above, below, or near normal precipitation, the improvement is based on the wet, cold pattern during the next two or three weeks and climatology.
Confidence for the West: Moderate

Across the Hawaiian Islands, relief has occurred since late November. Improvement should continue with the wet season underway.
Confidence for Hawaii: High