February - April 2009

Outlook Graphic: GIF   PDF 

Latest Seasonal Assessment - The drought over central and southern Texas has recently expanded mostly northward into Oklahoma, and is expected to either persist or intensify during the next three months. In the West, drought is forecast to persist over much of California. This is primarily because the main storm track is forecast to shift northward for the late winter, affecting mostly Oregon and Washington. Across the northern tier of states, signals from La Niña composites favor at least limited improvement for northwest Montana and for southwestern North Dakota. For the Great Lakes area, improvement in current drought conditions is expected for central Wisconsin, though prospects for significant relief are less likely over northern Wisconsin and adjoining upper Michigan. Small areas of improvement are also indicated across portions of the upper Ohio Valley and central Appalachians, with some improvement expected over the southern Appalachians/Piedmont area. In the southern Atlantic region, the Feb-Apr 2009 precipitation forecast shows a tilt in the odds for drier than normal conditions. This results in drought expansion from Florida into coastal Georgia and South Carolina.

Tools used in the Drought Outlook included the official precipitation outlook for February-April, 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 (CAS) moisture, and climatology.

Recent heavy precipitation across the Eastern U.S. has resulted in much improved conditions across the Ohio Valley and the central and southern Appalachians. Across the coastal Southeast, drier conditions have recently prevailed, especially across northern and central Florida, where streamflow values have been abnormally low. The Climate Prediction Center is calling for below average rainfall during both the month of February 2009 and the season of Feb-Mar-Apr 2009. The prominent dry signal over the Southeast (as well as the Ohio Valley wet signal) is consistent with historical La Niña cases. In addition, the Drought Outlook favors a slight expansion of dryness across coastal South Carolina during this forecast period. Some improvement is noted over the southern Appalachians/Piedmont area, which falls in between the anticipated dryness near the coast and wetness over the Ohio Valley.
Confidence for upper Ohio Valley: High
Confidence for the southern Appalachians: Moderate
Confidence for Florida and southeast Georgia: High

In Wisconsin and adjacent portions of Minnesota and upper Michigan, the best chances for improvement are for the southern areas which have been closer to the storm track over the Midwest in recent weeks. More northerly areas should still experience some improvement, especially with the near-term forecasts of Alberta Clippers moving across the area.
Confidence for Great Lakes region: Moderate

Across the southern Plains, some expansion of the Texas drought area is forecast. This is based on recent trends, medium-range forecasts and La Niña soil moisture composites. La Niña composites show that there is a tilt in the odds for dryness for the upper Texas coast during late winter. Higher rainfall climatology, as well as the 2-week total precipitation from the two gfs model runs noted above suggest that the dryness will not expand across northeast sections of Texas. Confidence decreases a bit across the southern Plains in April, as severe weather events begin to increase.
Confidence for southern Plains: High in western areas; moderate in eastern areas

In southeast Colorado, climatology favors persistence, while in southwest North Dakota, La Niña-related storminess should lead to improvement in the current drought.
Confidence for North Dakota and southeast Colorado: Moderate

In northwest Montana, La Niña-related storminess is expected to be offset somewhat by the climatological rain shadow just east of the Divide. Therefore, some improvement is forecast.
Confidence for northwest Montana: Moderate

Across the widespread drought areas covering California and the Great Basin, minor revisions were made to the previous outlook, released on December 31st. Based on La Niña composites and the latest model guidance for the next couple of weeks, prospects for improvement are slim for most of California and Nevada. It is thought that the mean jet stream and associated storm track will reside mainly north of this area. A small area of some-improvement is likely over the northwestern part of the state.
Confidence for the West: Moderate

For Hawaii, significant relief has occurred during the past few weeks. With the wet season well underway and the possibility of Kona Lows during La Niña winters, improving conditions are deemed the best bet.
Confidence for Hawaii: High