Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for April through June 2018 (AMJ), various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), the weeks 3-4 outlooks from CPC, dynamical models at the seasonal time scale, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for the AMJ season, and initial conditions (the U.S. Drought Monitor valid March 13, 2018).
Drought intensity remained steady or intensified by 1-category throughout the West during the past 30 days. According to preliminary information from the National Centers for Environmental Information (NCEI), California had its 2nd driest winter on record with only a third of its average precipitation from December 2017 through February 2018. As of March 13, snow water content across the Sierra Nevada Mountains is running 32 to 40 percent of average for this time of year. These snow water content values are likely to increase during the remainder of March as a series of cold storms enter the West. Due to the favorably wet conditions during the 2016-17 water year, many of California reservoirs are near or slightly above normal. AMJ is an increasingly dry time of year for California and the driest three-month period for the desert Southwest. Based on climatology and an increased chance of above-normal temperatures and below-normal precipitation during AMJ, persistence is forecast for the ongoing drought areas of the West. Development is forecast for parts of California, Nevada, and Oregon where snow water content values remain below-average and March precipitation amounts are not expected to be as high as adjacent areas.
Forecast confidence for the West is moderate.
Severe to extreme drought continues across southern Colorado with abnormal dryness for northern parts of the state. The highest odds for below-normal precipitation during AMJ are forecast across southwest Colorado. Given the below-average snow water content values and increased chances for above-normal temperatures during the spring, persistence and development is the most likely outcome for Colorado.
Short-term drought continues to worsen for much of Kansas with extreme drought (D3) designated in southwest Kansas. Drought is expected to intensify across southwest Kansas during the next few weeks due to continued dryness and periods of high winds. AMJ is an increasingly wet time of year for the central Plains and the most likely area to experience improvement is eastern Kansas.
A wet February resulted in drought improvement across parts of Montana and eastern South Dakota. Snow water equivalent amounts are currently above 2 inches across most of eastern Montana which bodes well for continued improvement this spring. AMJ is an increasingly wet time of year for the northern Great Plains with 40 to 50 percent of their annual precipitation typically occurring during this three-month period. The seasonal outlook indicates a slight tilt in the odds for above-normal precipitation for much of eastern Montana and the Dakotas. Based largely on the wetter climatology during AMJ and beneficial snowfall recently, improvement or removal is expected across the northern Plains by the end of June.
Forecast confidence for the High Plains is moderate.
A sharp gradient of precipitation occurred across Oklahoma since mid-February with the southeast corner of the state receiving as much as 15 inches of rainfall with little or no precipitation across the Panhandle. Therefore, drought was eliminated across southeast Oklahoma while drought remained steady or worsened for the western third of the state. Drought conditions vary throughout central and west Texas with extreme drought (D3) ongoing across the Texas Panhandle. A lack of precipitation combined with above-normal temperatures and periods of high winds during the remainder of March is likely to result in worsening drought conditions across the southern high Plains. Based on the seasonal outlook favoring below-normal precipitation and above-normal temperatures, drought persistence or development is forecast for western Oklahoma along with western and southern Texas.
Forecast confidence for the Southern Region is moderate.
Small areas of moderate drought (D1) are designated for parts of the middle Mississippi Valley and northern Minnesota. During the past 30 days, much of the Midwest received above-normal precipitation with surplus amounts of more than 4 inches across southern parts of Illinois and Missouri. Based on this recent wetness and the increasingly wet time of year during AMJ, removal of ongoing drought is expected.
Forecast confidence for the Midwest is high.
Although the Tennessee Valley and southern Appalachians experienced drought removal during the past month, drought remained or slightly expanded across southern Georgia and the South Carolina Lowcountry. Without a wet signal among the tools at any time scale, persistence and continued expansion is most likely across these areas. Abnormal dryness continues to expand across the Florida peninsula. Although drought development is anticipated during the next month for this region, it is not expected to persist through the end of June due to the high rainfall amounts that typically occur during that month.
Small areas of drought are noted in parts of the mid-Atlantic. Removal is forecast for these areas since precipitation averaged at or above-normal during the past 30 days and additional precipitation is expected through the end of March.
Forecast confidence for the Southeast is moderate.
The southern Alaska Panhandle is designated with short-term drought, while abnormal dryness is posted for southern mainland Alaska including the Kenai peninsula. Impacts for these areas include decreasing reservoir levels and reduced hydroelectric output. Without a wet signal among the precipitation tools, persistence is forecast for the southern Alaska Panhandle. Development is forecast for parts of southern mainland Alaska and the Kenai Peninsula where abnormal dryness coincides with enhanced odds for below-normal precipitation in the seasonal outlook.
Hawaii and Puerto Rico are drought-free and none is expected to develop through the end of June.
Forecast confidence for Alaska is low.
Forecaster: Brad Pugh
Next Seasonal Drought Outlook issued: April 19, 2018 at 8:30 AM EDT