Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for June through August 2019 (JJA), 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 Week 3-4 outlooks and tools from CPC, dynamical models at the monthly and seasonal time scales, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for the JJA season, and initial conditions such as soil moisture. The oceanic and atmospheric conditions reflect weak El Nino conditions and El Nino is likely to continue through the Northern Hemisphere summer 2019 (~70 percent chance).

Precipitation has averaged at or above normal throughout much of California, the Great Basin, and the Southwest since the start of the current Water Year (October 1, 2018). Basin average snow water content (SWC) is also above average across these areas, ranging from 103% to 437% of average. The ample precipitation and snowfall this Water-Year-To-Date (WYTD) resulted in major drought reduction throughout much of the Western region. According to the U.S. Drought Monitor, drought coverage (D1-D4) in this region decreased from 59% at the start of October 2018 to 4.2% by early May 2019. For areas that are still in drought, such as New Mexico and northeast Arizona, drought improvement and/or removal is forecast. This is supported by CPC's extended range forecasts, monthly and seasonal precipitation outlooks, valid for June and JJA, respectively. The onset of spring-summer snowmelt and summer monsoon will also assist in the mitigation of residual drought across these areas. In the Pacific Northwest, however, prospects for significant improvement are poor after the next several weeks. SWC ranges from 27% to 95% for the area that includes western and central Washington and far northwestern Oregon. WYTD values mostly range from 50%-90% of normal, with a few spots as low as 25% to 50%. Precipitation deficits of 12-16 inches are common across this region for the past 90-days. USGS 28-day stream flows are low, with values in the lowest quartile of the historical distribution. Based on SWC, WYTD deficits, and stream flow considerations, and both the June and JJA official precipitation outlooks favoring below normal precipitation and above normal temperatures; and the fact that the rainy season out West is over, drought persistence is favored for north-central Washington, with drought development indicated elsewhere.

Forecast confidence is moderate to high for drought persistence and development across the Pacific Northwest, and moderate for the remaining drought areas in the West.

The northern and central Great Plains remain drought-free, and above normal precipitation this winter resulted in major flooding along the Lower to Middle Missouri River Valley. Drought development is not anticipated during the outlook period at this time, but these areas are climatologically vulnerable to fast-developing drought with multiple weeks of insufficient rainfall and above average temperatures during the late spring and summer. Small areas of moderate drought (D1 on the U.S. Drought Monitor) remain over north-central Wyoming (low snowpack associated with the Big Horn Mountain Range). However, June and JJA climatologies, and the CPC precipitation outlooks for both June and JJA favor the removal of this drought.

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

The South region has remained drought-free. During the past 30 days, precipitation surpluses exceeded 4 to 15 inches across large portions of the Middle and Lower Mississippi Valleys, with soil moisture ranking at or above the 95th percentile. The monthly and seasonal precipitation outlooks from CPC, and climatology in general, favor near to above normal soil moisture conditions across most areas. Drought-free conditions across the South is anticipated.
 
Forecast confidence is moderate to high across the South.

Moderate to major flooding continues across parts of the Midwest region. During the past 90 days, precipitation surpluses exceeded 8 inches across portions of the Midwest and Ohio Valley, with soil moisture ranking at or above the 95th percentile for this time of year. Given such wet initial conditions and coming wet season, drought development is unlikely during the outlook period. However, subsequent monthly Outlook will closely monitor for any fast-developing abormal dryness or drought.

Forecast confidence is moderate to high for the Midwest Region.

Moderate drought currently exists over southeastern Georgia and adjacent parts of coastal South Carolina. Precipitation deficits in southeastern Georgia are on the order of 2-6 inches for the past 3-months. The CPC June and JJA precipitation and temperature outlooks favor above normal temperatures with no strong precipitation signal during both June and JJA. Therefore, drought persistence is favored.

Forecast confidence is low for the Southeast Region.

The Northeast region has remained drought-free since early November. Based on wet initial conditions, near to above average soil moisture values, and the absence of a dry signal among CPC's monthly and seasonal precipitation outlooks, drought development is unlikely through the end of August.
 
Forecast confidence is moderate to high for the Northeast Region.

Moderate to severe drought coverage remained nearly steady along the southern Alaska Panhandle this past winter and early spring. Since JJA is a relatively drier time of year, CPC's June and JJA outlooks favor below normal precipitation and above normal temperatures over these areas, persistence of this long-term drought is forecast, along with drought development possible for parts of the northern Panhandle region.

Forecast confidence is high for Alaska.

The increasingly persistent trade winds imply favorable precipitation for windward slopes of Hawaii. However, the outlook for leeward slopes, which are located in rain shadow areas downwind of the mountainous topography, favors drought persistence and/or development. The Seasonal Drought Outlook attempts to highlight broad-scale drought features, and not localized microclimates. It is interesting to note however, that the Kona Coffee belt area near the western coast of the Big Island, at an approximate elevation range of 1000-3000 feet, is the only leeward area of Hawaii that typically experiences its rainy season during the summer.

Forecast confidence is moderate to high for Hawaii.

Drought coverage across Puerto Rico peaked at 42.66 percent at the beginning of March, but decreased to 16 percent as of May 7. Although the climatology becomes increasingly wet during June and JJA, dry signals in the monthly and seasonal forecast tools favor drought persistence.

Forecast confidence is low for Puerto Rico.

Forecaster: Yun Fan

Next Seasonal Drought Outlook issued: Jun 20, 2019 at 8:30 AM EDT