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Climate Prediction Center


April - June 2003


Latest Seasonal Assessment - A massive storm system produced drought-easing rain and snow across western and central parts of the country during March 17-19, including 3 to 7 feet of snow in the front range mountains and foothills of Colorado. Water supply prospects improved in the Colorado River Basin, but significant long-term moisture deficits still prevailed across much of the West, and only limited additional improvement is expected in the next several months. Areas with the best chances for improvement include the Southwest and Pacific Northwest due to the seasonal forecast for wetter-than-normal conditions. Additional storm systems forecast later in March should also benefit parts of the Great Basin and central and northern Rockies, helping pastures and rangelands and local agriculture. Improvements to water supplies in the West will be limited due to the duration and severity of the drought and diminishing prospects for snowfall after March or April. Water shortages are expected to continue throughout the period. From Utah to Wyoming and Montana and eastward to the Dakotas and Nebraska, drought should largely persist, although some short-term improvement is seen. Odds also favor the continuation of drought from Iowa into Michigan, with spotty relief expected. In Maine, ample late-winter snowpack will temporarily boost soil moisture, but the long-term drought is expected to continue. In Hawaii, some easing of drought is forecast.

Discussion for the Seasonal Drought Outlook

The outlook calls for limited improvement for large areas of the West where recent rain and snow has reduced long-term precipitation deficits. The depiction for the West reflects the tradeoffs between the long-term deficits and unfavorable water supply forecasts versus recent favorable trends, short-term forecasts, and the seasonal precipitation outlook for April-June. Given the severity of the long-term deficits and the fact that the winter snow season is nearing its end, only limited improvement for the hydrological drought is anticipated. Nevertheless, recent or forecast rain and snow will benefit soil moisture for non-irrigated agriculture and reduce wildfire danger this spring. Since last month, the forecast for western Arizona and southern California has become less optimistic as we go into the dry season and the odds for significant precipitation decline. The area of persisting drought has expanded in Utah to reflect poor water supply prospects due to below-normal winter snows. The constructed analogue soil moisture (CAS) forecast also implies continuing dryness in this area. The major storm that brought heavy snows to Wyoming and Colorado on March 17-19 boosted water supply prospects in both states and throughout the Colorado River Basin. Looking out into spring, the odds for significant change in the status of the long-term drought decline as the snow season wanes; hence, the forecast for limited improvement.

Recent trends and historic El Niño composites suggest improving soil moisture trends this spring in the central Plains and diminishing odds for improvement moving northward into the Dakotas. The mid-March storm increased soil moisture across the Plains and the Midwest and more relief is expected later in the month, but the CAS forecasts and precipitation composites based on El Niño and North Pacific SST patterns imply a tendency for dryness to persist in at least parts of the region. As a result, drought is forecast to remain in the upper Midwest. Forecast confidence is low given the time of the year and the recent change in circulation pattern leading to a wetter near-term outlook.

Heavy late-winter snowpack in Maine will mitigate impacts from long-term drought, but there is a tendency for drought to persist into spring there as El Niño transitions to neutral conditions. The result is the forecast for limited improvement.

The odds for dryness diminish in Hawaii as the El Niño fades, but the climatological trend toward drier weather this time of the year results in a forecast for limited drought improvement.

NOAA/ National Weather Service
NOAA Center for Weather and Climate Prediction
Climate Prediction Center
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Page Author: Climate Prediction Center Internet Team
Page last modified: March 20, 2003
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