NOAA Drought Outlook Monthly – May

    Photo: L. Brian Stauffer, University of Illinois

    Heavy precipitation during late April and into the beginning of May is likely to result in either drought removal or improvement across northeast Colorado along with central to eastern Texas. Persistence is likely for western Texas and also throughout the long-term drought areas of the West.

    Recent dryness and elevated probabilities of below normal precipitation and above normal temperatures during May favor a return of drought to northwest Oklahoma and parts of the Texas Panhandle. Development is also favored to occur across southern Idaho and eastern Oregon by the end of May.

    Broad persistence is favored for much of the northern to central Great Plains due to the long-term drought conditions and varying precipitation forecasts throughout the month. The first week of May is likely to be mostly dry, while the week-2 precipitation outlook on April 30 calls for elevated probabilities of above normal precipitation.

    Forecast confidence is low for the northern to central Great Plains since May is one of the wetter months of the year. Persistence is also forecast for Iowa, Wisconsin, and most of Michigan. Prospects for drought removal increase farther to the south across Illinois, Indiana, and Ohio due to rainfall predicted during the first week of May and larger probabilities (above 40 percent) for above normal precipitation in the updated May outlook.

    United States Monthly Drought Outlook Graphic - click on image to enlarge

    Click Image to Enlarge

    Development for the eastern U.S. is most likely across parts of the Carolinas due to increasing short-term precipitation deficits and a relatively dry start to the month. Any lingering drought across southwest Florida is likely to end during May or shortly thereafter. Removal is also forecast for northwest Pennsylvania and western New York, while persistence is more likely for New England.

    Drought persistence is forecast for the Big Island of Hawaii and development remains favored during the early summer. Alaska is forecast to remain drought-free through the end of May. Due to a recent drying trend and the latest precipitation forecasts, persistence or development are favored for Puerto Rico.

    Forecast confidence for the Western Region is high.

    • Long-term drought remains entrenched throughout a majority of the West. According to the U.S. Drought Monitor valid on April 27, nearly a third of this region is designated with severe (D2) to exceptional (D4) drought.
    • Since May begins the dry season for much of the West, persistence is likely.
    • Based on low soil moisture (below the 20th percentile) and the May outlook calling for elevated probabilities of below normal precipitation, development is forecast for southern Idaho and eastern Oregon.

    Forecast confidence is high for removal in northeast Colorado but low for the remainder of the High Plains Region.

    • The wet March continued into April across the Front Range of the Colorado Rockies and adjacent high Plains where 30-day precipitation surpluses are 1 to 3 inches.
    • Based on improving conditions such as soil moisture, generally above the 20th percentile, and additional precipitation forecast during the first week of May, drought removal is likely for northeast Colorado along with south-central Wyoming.
    • Please note that the seasonal outlook (May-June-July) favors below normal precipitation and above normal temperatures. Therefore, worsening drought conditions may return later in June or July.
    • The remainder of the north-central Rockies and Great Plains have received near to below average precipitation during April.
    • Persistence is more likely for the northern and central Great Plains as it is expected to take more than a month for broad improvement to occur for these long-term drought areas. However, forecast confidence is low since May is one of the wetter months of the year when the northern and central Great Plains receive 14 to 20 percent of their annual precipitation.
    • The one exception to the persistence is southeast South Dakota where conditions have improved this spring. Based on this factor and the wet May climatology, removal is favored for that part of South Dakota.
    • Drought is expected to return to southwest Kansas by the end of May due to elevated probabilities of below normal precipitation and above normal temperatures during May.

    Forecast confidence is moderate for the Southern Region.

    • Widespread, heavy rainfall (1 to 3 inches, or more) from April 27 to 30 along with additional rainfall at the beginning of May are likely to result in drought improvement or removal across central and eastern Texas.
    • Farther to the west and south, including the Rio Grande Valley, persistence is forecast for areas that largely missed out on this beneficial rainfall and soil moisture is below the 5th percentile.
    • Following an end to the drought across northwest Oklahoma and parts of the Texas Panhandle earlier this spring, April became increasingly dry. Based on this recent dryness and elevated probabilities of below normal precipitation and above normal temperatures during May, drought is expected to return to northwest Oklahoma and expand across the Texas Panhandle.

    Forecast confidence is low for the Midwest Region.

    • Long-term drought is more likely to persist across parts of northern Iowa. However, forecast confidence is low given the wet time of year and mixed precipitation forecasts at various time scales.
    • Farther to the east across the Great Lakes, the May outlook favors above normal precipitation albeit with relatively low probabilities.
    • Removal is most likely from northeast Illinois eastward to southern lower Michigan and northern Ohio where probabilities exceed 40 percent for above precipitation in the updated May outlook.
    • Persistence is favored for the remainder of Michigan and southern Wisconsin.
    • This south to north depiction of removal to persistence is consistent with predicted rainfall amounts during the first week of May. Near to above normal rainfall expected during the first half of the month preclude designation of any development for the Midwest.

    Forecast confidence is moderate for the Southeast Region.

    • Abnormal dryness (D0) expanded across parts of the Carolinas and Georgia due to increasing 30 to 90-day precipitation deficits.
    • Based on a relatively dry first half of the month along with periods of above normal temperatures, development is expected for most of the current D0 area.
    • Along and west of the Savannah River, development is less likely as those areas are not quite as dry.
    • Removal is forecast for the small D1 (moderate drought) area in southwest Florida which is consistent with the May precipitation outlook. As the convection season ramps up around the beginning of June, any lingering dryness across the Florida Peninsula is likely to be short-lived.

    Forecast confidence is moderate for the Northeast Region.

    • Beneficial rainfall at the end of April along with a likely wet first half of May favor removal for northwest Pennsylvania and New York.
    • Persistence is more likely across New England due to larger precipitation deficits (more than 8 inches) dating back 6 months.
    • Although small areas of removal may occur across Massachusetts, New Hampshire, and Vermont with any heavy rainfall, broad persistence is more likely given the longevity of the drought conditions.

    Forecast confidence is high for Alaska.

    • Due to a lack of snowfall this past winter, abnormal dryness (D0) is designated for parts of northern and eastern Mainland Alaska.
    • Based on an increasingly wet climatology during May, this D0 area is unlikely to worsen to moderate drought (D1). Alaska is likely to remain drought-free.

    Forecast confidence is low for Hawaii.

    • Abnormal dryness (D0) expanded in coverage across the Hawaiian Islands during April. Forecast confidence is too low to designate development for any specific area on a monthly time scale, but degradation to moderate drought is expected through the early summer.
    • Persistence is likely for the ongoing drought area on the Big Island.

    Forecast confidence is moderate for Puerto Rico.

    • During late April, moderate drought (D1) was introduced to eastern Puerto Rico and Vieques and slightly expanded across southwest Puerto Rico.
    • Since the latest model guidance indicates a continued drier-than-normal pattern through at least early May, persistence is favored.
    • Development is most likely across southern and eastern Puerto Rico where 28-day average streamflows are the lowest.



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