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Climate Prediction Center


January - March 2011


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Latest Seasonal Assessment - During the past several weeks, widespread precipitation overspread much of the western U.S., with much above average amounts extending from southern California and Nevada northeastward into the northern Plains and upper Midwest. The heavy rainfall and snow ameliorated lingering drought in the Great Basin and north central Rockies. Areas of heavy rainfall were also observed along the western and central Gulf Coast, bringing localized drought relief, while other areas of the Southeast experiencing severe drought missed out on significant rainfall. Continued dryness promoted expanding drought conditions across the southern and central Plains and far southern Arizona. With moderate to strong La Niña conditions expected to continue through the northern hemisphere winter season, strong consideration was given in this outlook to climate anomalies associated with the cold ENSO phase. Therefore, drought expansion or intensification is expected across the southern Atlantic states. To the north, storm systems frequently translate across the Ohio Valley region into New England during La Niña winters, increasing the odds for drought improvement from eastern Arkansas and western Tennessee northward into the eastern Corn Belt. Drought persistence is expected across the southwestern U.S., with additional developing drought possible in the central and southern High Plains. Increased odds for above median precipitation during the rainy season in Hawaii favor some improvement of protracted drought conditions.

Discussion for the Seasonal Drought Outlook

Tools used in the U.S. Drought Outlook (USDO) included the official CPC precipitation outlook for January 2011 and the long lead forecast for January - March 2011, 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, the Climate Forecast System (CFS) seasonal precipitation forecasts, La Niña composites for the December - February season, the four-month Palmer drought termination and amelioration probabilities, climatology, and initial conditions.

Areas of heavy rainfall overspread portions of the immediate Gulf Coast, with the heaviest totals, exceeding 4 inches, observed along the northern coastline of Texas. Above average rainfall also fell along a line from central Mississippi through eastern Tennessee, generally outside of the core drought areas of the Southeast. Elsewhere, however, below average rainfall persisted, particularly in Florida, Georgia, and northern Louisiana. Short term forecasts indicate the potential for widespread rainfall across the Southeast, with accumulations generally between 1 and 2 inches in most locations. The CPC 6-10 and 8-14 day outlooks indicate near median rainfall, and the monthly and seasonal outlooks both favor below median precipitation, particularly across Florida. While the short term rainfall may slow additional drought expansion, strong dry climate anomalies associated with La Niña promote persistence of existing drought, with further drought development most likely in Florida and along the southern Atlantic coastline. The forecast becomes more complicated from the southern Appalachians through far southeastern Oklahoma, as a tight anomaly gradient exists between the Southeast and the Tennessee and Ohio Valleys, where above median precipitation is favored. While the presence of a strong La Niña tends to expand the dry anomalies northward, intraseasonal factors such as the Arctic Oscillation, which is currently in a negative phase, can counteract the northward expansion of the dry anomaly. For this outlook, a boundary of some improvement between drought persistence to the south and improvement to the north runs from southern Arkansas through Tennessee's border with Alabama and Georgia.
Forecast confidence for the Southeast is high for the coastal plain, and low from southern Arkansas through the southern Appalachians.

A second winter storm generated additional snowfall across the northern Plains and upper Midwest following the major winter storm in early December. Snow depths across the small remaining drought area of extreme northeastern Minnesota remain near 20 inches, with liquid equivalents between 3 and 6 inches. Due to the already extensive snowpack, further drought improvement in this region is likely.
Forecast confidence for northeastern Minnesota is high.

Near average precipitation, falling as both snow and rain, overspread the drought areas of the middle Mississippi Valley and Indiana during the previous two weeks, with no remaining snowpack. CPC 6-10 and 8-14 day outlooks, however, indicate enhanced odds of above median precipitation. Based on pronounced climate anomalies associated with La Niña, the CPC monthly and seasonal outlooks both favor enhanced above median precipitation probabilities as well. Storm tracks during a La Niña winter strongly favor the Ohio Valley region, particularly during the January-March period. Based on the favorable seasonal outlook, further drought amelioration is forecasted from northeastern Arkansas through Indiana.
Forecast confidence for the middle Mississippi and Ohio Valleys is high.

Outside of a band of above average precipitation extending from northern Texas through southeastern Oklahoma, widespread dry weather persisted across the central and southern Plains. Drought conditions expanded or intensified across western Texas, Oklahoma, and Kansas. Short term forecasts indicate a potential for snowfall across portions of the northern and central Plains as an Arctic air mass pushes southward out of Canada. Portions of northwestern Kansas may receive more than 0.5 inch liquid equivalent of snow, but little precipitation is expected to push into the southern High Plains. The CPC 6-10 and 8-14 day forecasts favor dry conditions across Texas, and the seasonal outlook indicates enhanced odds of below median precipitation across the southern High Plains. Based on these outlooks, drought persistence is expected, with additional drought development possible across northern Texas and central Kansas.
Forecast confidence for the central and southern Plains is moderate.

A series of massive winter storms brought much above average precipitation to California, Nevada, northwestern New Mexico, and the central Rockies during the previous two weeks. Lingering drought conditions eased across the Great Basin, northeastern California, and Wyoming. Further south, little precipitation fell across drought areas in far southern Arizona and southern New Mexico, where drought conditions continued to expand. While the revised CPC monthly outlook for January reflects greater odds for above median precipitation across the southwestern U.S., short and medium range forecasts indicate a return to near or below average precipitation. The seasonal outlook indicates greater odds for below median precipitation and above median temperatures across the southern Four Corners states. Based on these forecasts, which reflect climate anomalies observed during La Niña winters, drought persistence is maintained in this outlook, with small areas of some improvement across northern Arizona and south central Colorado, which received significant precipitation during the previous two weeks.
Forecast confidence for the southwestern U.S. is moderate to high.

Recent early season rainfall improved drought conditions across the western Hawaiian islands. During a La Niña winter, climate anomalies favor enhanced precipitation across Hawaii, but not with a high frequency of occurrence. As the rains pick up in the January-March period, the possibility for drought improvement increases, but significant improvement is more uncertain, since drought conditions are entrenched. Some improvement is indicated in this outlook.

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NOAA Center for Weather and Climate Prediction
Climate Prediction Center
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Page Author: Climate Prediction Center Internet Team
Page last modified January 6, 2011
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