Tools used in the U.S. Monthly Drought Outlook (MDO) included the updated Climate Prediction Center (CPC) temperature and precipitation outlooks for April, 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 CPC forecasts released on March 31, CFSv2 monthly forecasts of temperature and precipitation, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for April, and recent precipitation.
According to the United States Drought Monitor (USDM) issued March 30th, moderate and severe drought (D1 and D2, respectively) are confined to southwestern and extreme southern parts of California. The Santa Barbara County Flood Control District indicates the Cachuma Reservoir, one of the few reservoirs in the entire state that continues to report well below-normal water levels is currently at 50.2 percent capacity. Snow Water Content (SWC) across the Sierras ranges upward of 175-200 percent of normal. Given the onset of the climatological dry season in April across California, little if any drought relief is anticipated for these lingering drought areas. The same is true for (primarily) southwestern Arizona, where moderate drought is currently depicted.
Forecast confidence for California and Arizona is high.
Applied Climate Information Service (ACIS) data from the National Drought Mitigation Center (NDMC) in Nebraska depicts near-normal precipitation for the northern High Plains region during the past 14-days. This long-term moderate drought area (D1) centered in the vicinity of the Black Hills has indeed been persistent. April climatology favors increased precipitation in this region. CPC's precipitation outlooks on time-scales out to one month in advance indicate considerable variability, and do not present a strong signal either way for relative wetness or dryness. The deciding factor for this area is the regional climatology, which tilts the odds towards some improvement.
Forecast confidence for the northern High Plains is low.
ACIS Departure from Normal Precipitation (DNP) during the past 14-days reveals a mixed pattern across the Central Great Plains (perhaps with a slight overall edge to wetness), and 1-2 inch precipitation deficits across the southern Lower Plains. ACIS temperature data for this same two-week period depicts temperatures ranging between 9-12 degrees F above normal for much of the southern Plains, and 6-9 degrees F above normal for much of the central Plains. Climatology favors increased wetness across the central and southern Plains in April, and springtime in general. There is decent support for a one-category improvement across the Lower Plains with the dynamical model solutions, and persistence or development of drought across portions of the High Plains.
Forecast confidence for the central and southern Great Plains is moderate.
ACIS DNP's for the last 14-days show a modest precipitation surplus in Missouri and northwestern Arkansas, a modest precipitation deficit in southeastern Arkansas, and a mixed overall pattern in Louisiana. Temperature anomalies for this same two-week period ranged from 6-12 degrees F above normal for most of the Lower and Middle Mississippi Valley. Heavy precipitation (2.0-3.5 inches) expected in the next week alone is thought to be enough to warrant a one-category improvement in this area. A dry pattern is expected for much of the remainder of the month.
Forecast confidence for the Middle and Lower Mississippi Valley is moderate.
Across the interior Southeast U.S., 14-day DNPs were weighted more towards the dry side of normal. ACIS 180-day precipitation deficits in the core of the long-term drought area of the southern Appalachians ranged from 8-12 inches or more. Temperature anomalies for this same period ranged from about 3-10 degrees F above normal. The outlook for this area is mostly "front-loaded" in the sense that much (if not most) of the predicted rainfall (2-3 inches) is forecast during the first week of April, followed by several weeks of drier weather. Near the coast from extreme northeastern Florida to extreme southern North Carolina, pre-existing drought is expected to persist, with the remainder of this area forecast to have drought development in April.
Forecast confidence for the Southeast is moderate.
In Florida, ACIS 14-day DNP's ranged from 0-3 inches below normal, with the greater deficits indicated over central and northern Florida. With the Sunshine State near the peak of its climatological dry season, and with no strong indications to the contrary, persistence and/or development of drought is expected.
Forecast confidence for Florida is high.
Across the Northeast and mid-Atlantic, 14-day DNP's depicted a modest precipitation deficit for most areas. Inspection of the 90-day and 180-day DNP's reveals a clear dichotomy of precipitation anomalies across this region, with significant deficits near the coast, and significant surpluses well inland. In the Week-1 period, WPC predicts at least 2-3 inches of precipitation across much of this region, making one-category improvements in the drought depiction very reasonable.
Forecast confidence for the mid-Atlantic and Northeast is moderate to high.
In Hawaii, the rainy season is coming to an end, and rapid drying is already in progress across the leeward slopes of the Big Island. Drought persistence is favored for that area. At the present time, there is no drought in Alaska. In south-central Puerto Rico, a small sliver of drier conditions has developed, but it is likely to disappear quickly with the approach of the climatological rainy season.
Forecast confidence for Hawaii is high.
Forecaster: Anthony Artusa
Next Monthly Drought Outlook issued: April 30, 2017 at 3pm EDT