Tools used in the U.S. Monthly Drought Outlook (MDO) included the official Climate Prediction Center (CPC) updated temperature and precipitation outlooks for January 2016, various short- and medium-range forecasts and models such as the 7-day precipitation totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC Extended-Range Forecasts (ERFs), Weeks 3 and 4 experimental outlooks, the NAEFS precipitation outlooks, dynamical models including the CFSv2 and GFS, climatology, El Nino composites, and initial conditions.

During the past 30-days, the Advanced Hydrologic Prediction Service (AHPS) analysis depicts that precipitation (liquid equivalent) averaged more than 8 inches above normal across western Oregon and western Washington. Portland, Oregon received more than 15 inches of precipitation from December 1-29 which is 10 inches above normal. According to the Western Regional Climate Center (WRCC) analysis, basin average snow water content is running from 125 to more than 200 percent of normal across the Cascades. The anomalous precipitation during December along with beneficial snowfall and recovery of reservoirs led to drought amelioration or removal across the Pacific Northwest. Additional removal of drought is expected across southwestern Oregon due to the very wet December coupled with a wet January climatology. Persistence is most likely across the remainder of Oregon and Washington, where precipitation anomalies during December were smaller, and precipitation tools ranging from the short-term to the monthly time scale offer either a weak or dry signal.
Forecast confidence for the Pacific Northwest is moderate.

The wet pattern during December extended south from the Pacific Northwest to northern California, including much of the Sierras. AHPS indicates 30-day surpluses of more than 8 inches north of Point Arena, California. The drought removal forecast across northern California is based largely on this wet December and a wet climatology during January. In addition, the NMME precipitation forecast indicates a slight tilt in the odds towards above-median precipitation during January. According to the WRCC, snow water content values are running 120 to 160 percent of normal across the Sierras. Despite this beneficial start to the snow season, persistence is most likely across this region along with interior California due the longevity of the drought and low reservoir levels. An active southern stream is likely to bring locally heavy precipitation to southern California during the first week of the New Year. The WPC 7-day precipitation forecast indicates local amounts exceeding 2 inches. Drought improvement is favored for parts of southern California, where short-term precipitation amounts are the heaviest. The CPC Week-2 and monthly outlooks also indicate enhanced odds for above-median precipitation across southern California. The desert Southwest is also likely to experience locally heavy rain and mountain snow with the active southern stream during early January. Improvement or removal is forecast across parts of Arizona where short-term precipitation amounts are forecast to be heaviest.  
Forecast confidence for California and the desert Southwest is moderate.

Although precipitation averaged above-normal across most of the Great Basin and northern Rockies during the past 30 days, mostly dry weather is forecast during the first week of the New Year. The January precipitation outlook calls for increased chances of below-median precipitation across Idaho, Montana, and Wyoming. Based on these precipitation forecasts, persistence is favored across the Great Basin and northern Rockies. Drought is expected to expand near the Big Horn mountain range of Wyoming and the high Plains of southeast Montana, where basin average snow water content are running around 50 percent of normal for this time of year. The persistence and development forecast across the northern Rockies is consistent with climate anomalies associated with the ongoing El Nino. 
Forecast confidence for the Great Basin and northern Rockies is moderate.

Persistence forecast for the small areas of drought across North Dakota, the Midwest, and Great Lakes region is based on a dry start to January, along with increased chances for below-median precipitation forecast by the CPC January outlook. Forecast confidence is reduced; however, since many of these drought areas experienced near or above-average precipitation during the past 30 days. 
Forecast confidence for North Dakota, the Midwest, and Great Lakes region is moderate.

During the final week of December, precipitation amounts ranged from 1.5 inches to 3.0 inches across the Northeast. Removal forecast for this region is based on this recent precipitation and a favorable winter climatology, although forecast confidence is tempered since long-term drought effects could persist in the absence of a clear wet signal. 
Forecast confidence for the Northeast is low.

During the past couple of months, abnormal dryness (D0) expanded across Hawaii to include parts of the Big Island, Kauai, and Oahu. Since El Nino conditions strongly favor suppressed convection and below-average rainfall across Hawaii during the winter, and dynamical model precipitation forecasts support this signal, development is forecast for areas currently designated with abnormal dryness on the U.S. Drought Monitor.
Forecast confidence for Hawaii is high.

Drought coverage and intensity remained nearly steady across Puerto Rico during the past month. San Juan is running near 1.5 inches below-normal during December. Since January is typically one of the drier months of the year, persistence is expected.
Forecast confidence for Puerto Rico is high.

Forecaster: Brad Pugh and Adam Allgood

Next Monthly Drought Outlook issued: January 31, 2016 at 3:00 PM EST