January - March 2004

Latest Seasonal Assessment - Frequent bouts of rain and snow from October into December eased dryness in the Pacific Northwest, and long-range forecasts indicate that wetness should continue in this area. As a result, the latest seasonal drought outlook shows continued improvement from eastern Washington and Oregon into northern Idaho and western Montana. To the east and south, across the Great Basin and the Rockies, as well as east of the Divide in Montana, drought improvement should be limited, as an extended period of storminess is needed to recover from major hydrological drought affecting this region. As of mid-December, a number of streams were at record low levels for the time of the year in Idaho, Nevada, Utah, Colorado, Arizona, New Mexico. Reported reservoir storage on December 1 was below normal in every western state except California, and less than one-half of normal in Nevada, New Mexico, Utah, and Oregon. Snow pack in mid-November was generally below normal in the Southwest but running closer to normal farther north, and was better than last year in many places. In Wyoming, for example, snow pack is up 24 percent from last year, but is only 93 percent of the long-term average. Over the Southwest, a tendency toward below-normal precipitation and above-normal temperatures through March should keep the current drought largely intact, so the outlook calls for drought to persist from southern Nevada and southeastern California into New Mexico. In the Plains, where drought extends from west and north Texas northward into the Dakotas and eastward into the Upper Mississippi Valley and parts of the Middle Mississippi Valley, the forecast for below-normal precipitation during January-March in the Kansas-Nebraska area means that drought is likely to persist in this region. Seasonal tendencies also suggest that drought should largely persist in western and central South Dakota, and that limited improvement can be expected in the area extending from Minnesota southward through Iowa into northwestern Missouri. The outlook for above-normal precipitation during January-March for much of Texas suggests some improvement for the drought affecting western and northern parts of the state. Also, continued drought relief is expected for the areas of lingering drought in Hawaii. Torrential rains of up to one foot or more in late November ended drought over many areas in the island chain.

Tools used in the drought outlook included: the official CPC long-lead precipitation outlook for January-March, the Palmer Drought Index probability projections for Febraury and various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts.

The drought forecast continues to call for improvement in the Pacific Northwest consistent with the forecast for above-normal precipitation during January-March and recent trends toward improvement in this area. Farther east and south, across the Intermountain states and the northern and central Rockies, the odds for drought relief are not as great, given the scope of the ongoing water shortages and the lack of a clear consensus among forecast tools for the long-term precipitation outlook. As a result, only some relief is forecast for this region. One positive sign is that the early season snow pack has risen to near or above normal levels in a number of mountainous areas. Also, the Constructed Analogue soil moisture forecasts for March suggest improvement from current conditions. In the Southwest, the official precipitation forecast for January-March shows a weak signal for below-normal centered in Arizona, and the temperature outlook shows above-normal across the region. Accordingly, the prospects for drought relief are less from southeastern California and southern Nevada eastward into New Mexico, and the outlook calls for the drought to persist. Persisting drought is extended eastward into most of New Mexico due to some SST-based statistical indicators pointing toward continued dryness, and the Palmer Drought projections for March suggesting little chance for improvement in large parts of the state. The forecasts for the Southwest assume that the marginal El Niño conditions expected this winter will not significantly enhance precipitation over this region.

In the central states, the official precipitation forecast for January-March calls for above-normal precipitation in western and central Texas, although with low confidence. Significant drought relief is unlikely this time of the year in west Texas, so only some improvement is indicated in the drought forecast. To the north, the official forecast for the season ahead calls for below-normal precipitation in Nebraska and Kansas, and the drought outlook depicts persisting drought in this area, with the persisting area extended northward into western South Dakota because of the climatological probabilities of continuing drought. The previous outlook called for improvement in much of Kansas, Nebraska, and South Dakota, but the dry weather experienced in the past month or so resulted in little change, and the odds for relief now lessen as we enter a drier time of the year.

Forecast improvement called for in last month's outlook did occur in Illinois and Wisconsin, but drought has continued in Minnesota and parts of the adjacent states. Climatologically, it is a time of the year where drought improvement becomes difficult, so the forecast has changed from general improvement to limited improvement. The Palmer Drought projections for March, for example, show that the north-central climate division in Minnesota has a 74 percent chance of recording a Palmer index of negative 3.0 or worse.

In Hawaii, forecast drought improvement did take place, as a couple of heavy rain events since mid-November wiped out much of the drought. Based on the trends, continued improvement is forecast for western parts of the Big Island and western Molokai, the two areas where the U.S. Drought Monitor continues to depict lingering drought.