January - March 2009

Latest Seasonal Assessment - Excluding the widespread drought areas of the West, only minor changes were made to the previous outlook, released on December 18, 2008. During December, significant drought relief occurred across the upper Ohio Valley and Southeast. Additional improvement can be expected across the upper Ohio Valley and southern Appalachians. In contrast, the moderate drought has recently expanded in west-central Florida. During the next three months, the expansion of drought should continue across the Florida peninsula and into southeast Georgia. As the wildfire season approaches, the expected drought development should be closely monitored. Across the Great Lakes region, frequent periods of snowfall have occurred during the past month. Improvement is forecast across southeast Minnesota, Wisconsin, and the upper peninsula of Michigan. Improvement is also forecast in southern and eastern Oklahoma, while drought should persist in south-central Texas and may expand. Persistence is forecast for the small drought areas in southeast Colorado, the northern high Plains, and northwest Montana. The forecast remains a challenge across the western drought areas. The wet, cold pattern during mid-December increased snow-water content values to near average for this time of year. With signals from La Niña composites favoring dryness during the next three months, persistence is forecast for central and southern California, southeast Oregon, and Nevada. Improvement or some improvement is forecast for parts of northern California where climatology is quite wet, while some improvement is forecast for southern Idaho, northwest Utah, and southwest Wyoming. It should be noted that any improvement in the western drought areas may not be realized until the spring snow melt commences. 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, La Niña composites, climatology, and initial conditions.

During December, substantial drought relief has occurred across the southern Appalachians and drought was eliminated in middle Tennessee, Alabama, and central Georgia. The watershed of Georgia’s Lake Lanier has received abundant rainfall, resulting in a two foot rise of the lake’s level since December 1. However, Lake Lanier remains 18 feet below full pool stage and the protracted hydrological drought will likely continue. The 6-10/8-14 day outlooks call for above normal precipitation in the upper Ohio Valley and southern Appalachians. Seasonal precipitation tools indicate that drought improvement should continue during the remainder of the winter, especially in 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. It should be noted that February and March are two of the wettest months in the southern Appalachians.
Confidence for the upper Ohio Valley: High
Confidence for the southern Appalachians: Moderate

In southeast Georgia and the Florida peninsula, climatology along with the CPC seasonal precipitation forecast indicates drought persistence or development. If drought development occurs, an increase in wildfire activity would likely occur during the spring. With La Niña composites strongly favoring dryness, confidence is relatively high in this forecast.
Confidence for southeast Georgia and Florida: High

In the Great Lakes region, the short and medium-range forecasts are fairly wet while the seasonal tools are noncommittal. La Crosse, Wisconsin established a record for most snow measured during December, dating back to 1908. The outlook calls for improvement due to the heavy snowfall during the past month with additional snow expected in the short and medium-range.
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 and to the northwest. 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 and southern Texas that are currently experiencing abnormal dryness.
Confidence for Texas: High in western areas; moderate in eastern areas

In the high plains of North Dakota and southeast Colorado, climatology favors persistence.
Confidence: High
In northwest Montana, the 6-10 Day forecast along with the CPC January precipitation forecast favors above normal precipitation. However, snow-water content values are near record lows for this time of year. Since the odds for recovery from these current values are low, persistence is forecast.
Confidence for northwest Montana: Moderate

Across the widespread drought areas covering California and the Great Basin, significant changes were made to the previous outlook, released on December 18. Heavy rain and mountain snow brought drought relief to southern California in December. Despite the recent pattern featuring wet and cold conditions, snow-water content values are near or even remain slightly below-average in California and Nevada. Based on La Niña composites and the latest model guidance for the medium-range, prospects for improvement are slim for the southern half of California and Nevada. In addition, no forecast tools indicate wetness during any time range. Therefore, drought persistence is now forecast for central and southern California, southeast Oregon, and Nevada. The forecast for some improvement remains unchanged in southern Idaho, northwest Utah, and southwest Wyoming, due to mixed signals from the tools. In northwest California, the forecast for improvement is maintained from the previous outlook as La Niña has less of a signal across northern California compared to the remainder of the state.
Confidence for the West: Low

Across the Hawaiian Islands, relief has occurred during the past several weeks. Improvement should likely continue with the wet season underway.
Confidence for Hawaii: High