Heavy precipitation during the past 30-days resulted in significant drought reduction from the Rocky Mountain states eastward to the Atlantic Coast, western Washington state, the southern Intermountain region, and a small portion of extreme southeastern California. A one-category degradation was noted primarily in northern and central California, far western Nevada, northwestern Wyoming, southeastern Georgia, and southern Florida.
The seasonal drought outlook (SDO) valid from November 15, 2018-February 28, 2019 is based on precipitation outlooks for all time ranges out to a season in advance (Dec-Feb 2018-19), the expectation of a weak El Niño this winter, and consideration of current stream flows and soil moisture.
With the wet season now well underway across the western contiguous U.S., and the expectation of a weak El Niño this upcoming winter, drought improvement and/or removal is deemed a good bet across the coastal Pacific Northwest, California, Arizona, New Mexico, southern Colorado, far western parts of Texas, and also parts of the Southeast.
Drought is forecast to persist across the interior Northwest, northern Rockies, northern High Plains, central Intermountain region, central Rockies, and parts of the south-central Plains. Residual drought was removed across northern New York, Vermont, and eastern Kansas.
A stormy pattern for southern Alaska is expected to bring improvement and/or removal to the drought currently in place over the southern Panhandle region. In Hawaii, there is no drought at this time. However, with the prediction of a weak El Niño for this upcoming winter season (DJF 2018-19), drought development is favored for the more vulnerable west-facing slopes of the Big Island, Maui, and Molokai. There is no drought in Puerto Rico at this time, and none is expected through the end of February 2019.
Forecast confidence is moderate for the Western Region.
- The onset of the rainy season across the western contiguous U.S. resulted in some improvement of conditions across western Washington during the month of October, and deterioration has come to a halt in Oregon. The coastal Pacific Northwest typically receives 40 to 50 percent of their annual precipitation during this three month outlook period (DJF).
- Northern California has seen a slow decline in conditions over the past 1-2 months, though climatology becomes increasingly favorable as this area typically receives 50 to 67 percent of their annual precipitation during the winter season (DJF). The same is true for coastal southern California.
- Precipitation outlooks through one month in advance generally favor above normal precipitation for California, but mixed results for Washington and Oregon.
- For the DJF season, weak tilts in the odds for above normal precipitation are predicted in California, and Equal Chances (EC) of below, near, and above normal precipitation are favored for both Washington and Oregon.
- The Seasonal Drought Outlook (SDO) supports improvement and/or removal of drought across California, based on climatology, most precipitation outlooks through the next 90-days favoring above-normal precipitation, and El Niño composites. The SDO also depicts improvement and/or drought removal across the coastal Pacific Northwest, based largely upon wintertime climatology.
- For the interior Northwest, improvement and/or drought removal is less certain, as El Niño winters are often associated with a storm track that is displaced well south of this region; hence the prediction for drought persistence.
- AHPS Percent of Normal Precipitation (PNP) values for the past 30-days across eastern Nevada and portions of the Four Corners states are highly variable. However, to a first approximation, dry percentiles (5-75 percent) characterize the western half of this region, and wet percentiles (110-400 percent) characterize the eastern half.
- USGS stream flows across this entire region (southwestern states) are either below or near normal for this time of year. Most precipitation outlooks through the DJF period favor a tilt in the odds towards above normal precipitation for the region, especially after the first 10 days or so. Accordingly, improvement and/or removal of drought is indicated for Arizona and New Mexico, though prospects do not appear as favorable farther north, warranting drought persistence.
Forecast confidence is moderate for the High Plains Region.
- The DJF season is typically a drier time of year for the High Plains region. During an average year, the High Plains of eastern Colorado can expect to receive only about 10-15 percent of its annual precipitation; even less (only 5-10 percent) can be expected in central North Dakota. For western Colorado, the values are close to normal (20-30 percent of the annual precipitation).
- During the past 30-days, PNP values of approximately 110-400 percent, 50-200 percent, and 10-50 percent were depicted by AHPS for eastern Colorado, central North Dakota, and western Colorado, respectively.
- Current streamflows average close to normal in eastern Colorado, near normal in central North Dakota, and fall within the lowest quartile of the historical distribution for this time of year across western Colorado. The precipitation outlook suite out through the next 90-days provides mixed indications.
- Based on climatology, ENSO considerations, and the suite of precipitation outlooks, improvement and/or removal of drought seems most likely for south-central and southwestern Colorado; and persistence is favored for northwestern Colorado and the Dakotas.
Forecast confidence for the Southern Region is moderate.
- During the last 30-days, the AHPS Departure from Normal Precipitation (DNP) map showed positive precipitation departures of 1-8 inches or greater over much of the Southern region, and negative precipitation departures of 1-2 inches were noted over extreme southern Texas and most of Oklahoma.
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- Only a few scattered areas of moderate drought (D1) remain in the region; over northeast Oklahoma, and the northern Panhandle region and far southwest part of Texas. This area typically receives only 5-15 percent of its annual precipitation during the winter season (DJF).
- With the prediction of El Niño this winter and its associated storm track, above normal precipitation is favored for much of the South; though EC is thought to be a better bet from eastern Oklahoma to Tennessee.
- The SDO therefore favors drought removal for the two small drought areas in Texas, but persistence for the two small drought areas in neighboring Oklahoma.
Forecast confidence is moderate to high for the Southeast Region.
- Only a few areas of abnormal dryness (D0) remain over the Midwest.
- For the localized drought areas that remain in the Southeast, most of the precipitation outlook suite favors above normal precipitation, or EC. These precipitation outlooks, coupled with good prospects for an El Niño-related storm track over the Gulf and Southern Atlantic Coast states this winter, favors the removal of any residual drought areas during this DJF season.
There is no longer any drought over the Northeast; only a few areas of abnormal dryness (D0) remain.
Forecast confidence is high for Alaska and moderate for Hawaii.
- Moderate drought continues along the southern Alaska Panhandle. Precipitation outlooks for all time scales out through the DJF season favor above normal precipitation, warranting drought removal.
- There is no drought in Hawaii and Puerto Rico at this time, but with the expectation of a weak El Niño this winter, drought development is possible for leeward (west-facing) slopes of the Big Island of Hawaii, Maui, and Molokai. No drought development is expected in Puerto Rico.