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Climate Prediction Center


December 2005 - February 2006


Latest Seasonal Assessment - Most drought-affected areas in the western states and Rockies should continue to experience moderate hydrologic drought through February 2006, with some limited periodic improvement. The only exceptions are central Idaho, where improvement may be more substantial and widespread, and parts of Arizona and New Mexico, where improvement seems less likely. Farther east, moderate to extreme drought should continue from the Wyoming High Plains eastward through most of northern Illinois, in portions of South Dakota, and across central and southern Texas. Winter is typically drier than other seasons in these areas, so the chances for substantial drought improvement are small. Drought should also continue to affect portions of the Great Lakes region, and a broad swath from eastern Texas northeastward through Tennessee and Kentucky, but with decent chances for periodic, limited improvement. Lake-effect and lake-enhanced snowfall is common and should at least temporarily ease drought impacts in the Great Lakes region at times, and a climatological increase in storminess from the southeastern Great Plains to the Upper South should bring opportunities for drought-easing precipitation to the region later in the period. Elsewhere, the entrenched drought and attendant local water shortages in the Carolinas should persist and might worsen as winter progresses, and farther south, some antecedent dryness and expected below-normal December 2005 - February 2006 precipitation should combine to spread drought into southern South Carolina, central and interior southern Georgia, southeastern Alabama, and most of northwestern Florida.

Discussion for the Seasonal Drought Outlook

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for December 2005 - February 2006, the drought termination and amelioration probabilities for February 2006, various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, and the soil moisture tools based on the GFS model and the Constructed Analogues for the season.

For areas from the Rockies westward to the Pacific Coast, substantial precipitation during the cold half of the year is critical. Ideally, snow piles up on the higher elevations before melting slowly as spring progresses, refilling the streams, rivers, and reservoirs that serve as the region's primary water sources. So far, the 2005-2006 water year is off to a good start in most areas currently experiencing moderate to severe drought (as depicted in the Drought Monitor). Most basins are at least slightly wetter than normal through November 16, 2005, with 125 to 160 percent of normal precipitation reported in southern and interior eastern Oregon, central and southern Idaho, western and southern Montana, and northwestern Wyoming. However, the water recharge season is only about 6 weeks old, and with a vast majority of the season still to come, the current short-term wetness will mean next to nothing if below-normal precipitation occurs during the next few months. Therefore, precipitation from the Rockies westward during this forecast period is critical and will be closely monitored. Unfortunately, below-normal precipitation is forecast throughout the region during the next 2 weeks, and the forecast models and statistical indicators for the ensuing 3 months (December 2005 - February 2006) do not consistently favor any particular scenario. As a result, the Drought Outlook for this region was largely driven by current conditions, the anticipated dryness during the next couple of weeks, and December - February climatology, all of which boils down to a forecast of continuing drought with some temporally and spatially limited improvement. Substantial drought relief by February 2006 is possible, but drought intensification is equally possible. It will depend on how the next several months unfold as a whole. It should be noted that, climatologically, chances for substantial drought improvement in the Washington Cascades are considerably higher than for most other drought-affected areas in the West, but with drier than normal conditions expected for the next couple of weeks, and with none of the tools strongly indicating wetter than normal December - February precipitation in the region, the area of expected improvement in last month's Drought Outlook was removed.

There are two exceptions to the limited-improvement forecast made for most of the West. First, improvement is being forecast for much of Idaho, where reports indicate that drought-related impacts are not as severe nor as widespread as in some other areas. Second, drought persistence or intensification is forecast for the drought-affected areas in Arizona and New Mexico, consistent with the consensus of the tools.

Farther east, drought is forecast to persist in a swath from the Wyoming High Plains eastward through most of the northern tier of Illinois, where drier than normal conditions are expected during the next 2 weeks. There are no strong indicators for either above- or below-normal December - February precipitation per se, but since this is a relatively dry time of year (particularly in the High Plains) and there are no indicators strongly pointing toward wetter than normal conditions, substantial drought relief seems unlikely by the end of February.

In the central and southern Great Lakes region, climatology indicates that a substantial reduction of long-term moisture deficits is unlikely by February, and the next 2 weeks are expected to be drier than normal. However, winter precipitation climatologically accounts for a larger proportion of the annual total here than in areas farther west, and additionally, with lake-effect and lake-enhanced snowfall relatively common, it seems likely that at least a temporary reduction of some drought impacts should occur over the course of the next few months.

Drought is expected to persist or possibly worsen across central and southern Texas. Winter is typically a relatively dry time of year for the region (at least until late in the period), and none of the objective indicators point toward widespread above-normal precipitation for the next 3.5 months.

In the swath of drought extending from eastern Oklahoma eastward through Tennessee and Kentucky, drought is expected to continue, but with a fair chance for limited improvement at times during the next few months. Moderate rains have already fallen since the last valid Drought Monitor issuance across Kentucky and Tennessee, which may lead to some areas of in next week's issuance. The last half of November looks to be drier than normal throughout the region, and thereafter, December - February precipitation indicators are mixed in the ArkLaTex region, and generally indeterminate across Kentucky and Tennessee. However, precipitation is climatologically on the upswing throughout the region during February, so a forecast was made that allowed for some chance of at least short-lived drought improvement.

Drought has become well entrenched across the Carolinas during the last few months, with short water supplies and mandatory water usage restrictions in place for several locales. The objective indicators point toward near- to below-normal precipitation for the next 3.5 months, and given the long-term nature of the moisture shortages affecting the region, relief seems unlikely and drought is forecast to persist or worsen through February 2006.

Finally, drought is expected to develop across much of southern South Carolina, central and interior southern Georgia, southeastern Alabama, and northwestern Florida by February 2006. This region is classified as abnormally dry in the most recent Drought Monitor, and a vast majority of indicators, including the official December 2005 - February 2006 outlook issued by the Climate Prediction Center, favor below-normal winter precipitation across the region.

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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: December 13, 2006
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