NOAA Drought Outlook Monthly – May

    Drought continues do divide the nation in half, as it approximately has for several months. Drought of varying degrees covers most of the country from the Great Plains westward, save for some small scattered regions in the Rockies and parts of the Pacific Northwest.

    In contrast, drought covers very little area from the Mississippi Valley eastward, affecting only the immediate central Gulf Coast, parts of the southern Atlantic States, and isolated spots in the Northeast.

    Drought also covers about half of Hawaii – mostly on central and eastern parts of the main islands – and two small areas in southernmost Puerto Rico.

    Over the past month, drought has persisted or worsened over most of the western half of the contiguous states. Only a few swaths across the northern Plains and Rockies, the upper Mississippi Valley, the Red River (south) Valley, and the lower Mississippi Valley saw more improvement than deterioration.

    Meanwhile, intensifying drought covered sizeable portions of the central and southern Plains and the southern half of the Four Corners States.

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

    Click Image to Enlarge

    May is one of the wettest months of the year across the Plains, northern Rockies, and western Great Lakes Region. Heavy precipitation is in fact forecast for at least early May in these areas, likely bringing some improvement to a large area in the Nation’s mid-section and the northern High Plains.

    In other drought areas across the western half of the country, drought is expected to persist or intensify, with some expansion into the parts of the Rockies not currently experiencing drought.

    In the eastern half of the country, most areas of drought are expected to improve, excepting in parts of South Carolina and Georgia. There, May is slightly drier than some other months, and there are no indications that any precipitation will be sufficient to improve conditions.

    In addition, drought conditions across Hawaii are expected to change very little during the month.

    Forecast confidence for the Western Region is high along the southern and western tiers, moderate in Utah and Nevada, and low farther north where climatology is wetter and the situation is primed for potential changes.

    • Drought covers a large majority of the Western Region. On April 26, over 90 percent of the region was experiencing some degree of drought, and extreme (D3) to exceptional (D4) drought covered more than one-third of the region.
    • The Outlook can be divided into 3 distinct areas. First, this is a climatologically dry time of year west of the Cascades, across most of California, and over New Mexico and Arizona.
    • Given how entrenched drought is, and the fact that less than 5 percent of annual precipitation falls during May, persistence or worsening is highly favored here with high confidence.
    • Across the northern Intermountain West, the Great Basin, and Utah, this is not a climatologically dry month, and that alone improves the odds that drought-improving precipitation will fall. However, little or no precipitation is expected during the first week of May, and none of the tools indicate the potential for precipitation heavy enough to improve things, especially given mostly above-normal temperatures.
    • The northern Intermountain West – where there are enhanced chances for above-normal precipitation on some time scales – have a better opportunity for improvement than areas farther south, but odds still favor no significant changes to conditions through the end of the month.
    • Lastly, across central and eastern Montana, May is a wet time of year, typically providing 15 to 20 percent of the annual precipitation total.
    • Recent heavy precipitation has induced some drought improvement in parts of the region, and with above-normal precipitation favored on some time scales (including the month as a whole), the improvement trend is expected to continue here, in contrast to the rest of the West Region.

    Forecast confidence is moderate to high for the High Plains Region.

    • Drought covers over 75 percent of the High Plains Region, with the most intense classifications (D3 or D4) affecting about 12 percent of the area.
    • May is one of the wettest months of the year across most of the High Plains Region, and there are enhanced chances for surplus May precipitation most of the central and northern Great Plains, plus adjacent northeastern Wyoming. Further, during late April and the first week of May, heavy precipitation (generally 1 to locally 3 inches) is expected from Kansas northward to the Canadian Border, and across parts of southeastern Wyoming and northeastern Colorado.
    • In these areas that are climatologically wet, are expecting a heavy precipitation event early in the period, and have enhanced chances for above-normal May precipitation as a whole, improvement or removal is forecast with moderate to high confidence.
    • In marked contrast, May is not a particularly wet time of year across the southwestern three-quarters of Colorado, and the outlook for May as a whole favors subnormal precipitation. Therefore, the only reasonable forecast here is for persistence or perhaps some deterioration, with drought expanding into the few areas in the state not currently experiencing drought.

    Forecast confidence is moderate to high for the Southern Region.

    • Drought covers a little over half of the Southern Region, mostly over central and western sections of Texas and Oklahoma, and along the immediate Gulf Coast. The May outlook favors above-normal precipitation across most of Arkansas and Oklahoma… below-normal precipitation through southern and western Texas… and there is no discernable tilt of the odds elsewhere.
    • In the short-term, heavy precipitation is expected across the northern half of this region. Between 2 and 5 inches are expected over most of Oklahoma east of the Panhandle during the first week of the month, and up to 2 inches can be expected near and immediately south of the Red River (of the south) and across parts of Arkansas.
    • In the short-term, forecast precipitation totals decline rapidly as one moves south of these areas, and only a few tenths of an inch at best are expected by May 7 in roughly the southern halves of Texas and Louisiana.
    • Climatologically, May is one of the wetter months of the year across Oklahoma and most of Texas, usually providing 10 to 15 percent of the annual precipitation.
    • In sum, the short-term forecast, the outlook for May as a whole, and climatology all coincide over the north half of the Southern Region, especially in Oklahoma. Improvement or removal is the only logical forecast here.
    • Areas farther south and along the Gulf Coast are expected to miss the heavy precipitation event in the short-term, and May precipitation as a whole favors neither significantly above- nor significantly below-normal precipitation.
    • In addition, May is not as markedly wet across the lower Mississippi Valley. So in these areas, persistence or perhaps worsening is expected, especially given the odds favoring a warmer-than-normal May.

    Forecast confidence is moderate to high for the Midwest Region.

    • In sharp contrast to areas farther west, less than 2 percent of the Midwest Region is currently experiencing drought, being confined to parts of northern and western Iowa.
    • May is somewhat wetter than most other months in the western half of the Midwest Region, typically bringing 10 to 15 percent of annual precipitation.
    • In the short-term, moderate to heavy precipitation is expected in the drought areas during the first week of May, and the outlook shows enhanced chances for a wetter than normal May as a whole.
    • Therefore, the only reasonable forecast is for drought to have even a smaller footprint in the region than it already has. Outside Iowa, there are no indications that May could be dry enough to spark drought development.

    Forecast confidence is low for the Southeast Region.

    • Drought is affecting about 16 percent of the Southeast Region; specifically, southern Florida, southern Georgia, the eastern Carolinas, and a couple small areas in Virginia. Only a few sections of southern Florida and most of eastern North Carolina are experiencing anything more intense than moderate drought (about 2 percent of the Region).
    • Most forecasts and tools are not robust with either wetness or dryness for May. The first week of the month should feature moderate precipitation (up to an inch) in most of Virginia, eastern North Carolina, and parts of southern Florida, likely improving conditions. Farther south, only a few tenths of an inch of precipitation are anticipated during the first week of May.
    • The 6 to 10 day outlook favors above-normal precipitation, but only slightly, and the week 2 forecast tilts slightly toward surplus precipitation in much of the Carolinas.
    • With no big storms on the horizon, and with May not tilting much toward wetness or dryness compared to other parts of the year, weak signals lead to a low confidence forecast.
    • The preponderance of the evidence leans toward conditions easing up at least somewhat by the end of May in most areas.
    • The drought-affected parts of South Carolina and Georgia are the exception. These areas are expecting only a few tenths of an inch of precipitation at best during early May, and the climatology for May leans very slightly toward dryness relative to the rest of the year.

    Forecast confidence is low for the Northeast Region.

    • Drought covers less than 1.5 percent of the Northeast Region, almost entirely in western Maine.
    • Neither abnormally wet nor abnormally dry conditions are favored for May as a whole. Light precipitation is expected in the short term (although the forecast has been volatile), and neither the 6-10 day outlook, the week 2 outlook, nor the weeks 2-4 outlook favor either wetness or dryness.
    • The recent trend has been toward slow improvement, however, and with the outlooks on all time frames favoring either wetness or near-normal precipitation, slow improvement is forecast to continue, though with low confidence.

    Forecast confidence is high for Alaska.

    • With no extant dryness and nothing to indicate a sustained period of subnormal precipitation anywhere in the state during May, Alaska should remain drought free.

    Forecast confidence is moderate for Hawaii.

    • In Hawaii, there may be changes to conditions coming during the summer, but there’s nothing to indicate that conditions will change substantially in May.

    Forecast confidence is low for Puerto Rico.

    • Improved conditions are slightly favored in the two small spots of moderate drought in southern Puerto Rico, based only on the fact that May is one of the two wettest months of the year.



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