Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for January 2016 and January - March (JFM) 2016, 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 NAEFS (North American Ensemble Forecast System) precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil Moisture (CAS), dynamical models (CFSv2, NMME, IRI, IMME, and ECMWF), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer drought termination and amelioration probabilities, climatology for the JFM season, and initial conditions. An El Nino (ENSO) Advisory remains in effect, with the December 10, 2015 ENSO Diagnostic Discussion indicating El Nino is expected to remain strong through the Northern Hemisphere winter 2015-16, with a transition to ENSO-neutral anticipated during the late spring or early summer 2016. Therefore, climate anomalies associated with El Nino played a substantial role in this outlook.


Drought improvement or removal is expected across California by the end of March 2016 due to the ongoing El Nino and a relatively wet climatology during the outlook period. Seasonal precipitation tools favor above-median precipitation across California during JFM which is consistent with El Nino winters. Typically, 35 to more than 50 percent of the annual precipitation occurs during JFM across California.  The Advanced Hydrologic Prediction Service (AHPS) indicates that above average precipitation has been observed across parts of northern California, north of Port Arena, during the past 30 days. Also, snow water content values are close to the mid-December average for the northern Sierras. A wet pattern is likely to continue across northern California during the remainder of December due to a persistent, upper-level trough. Due to the wet start to the winter and an addiitional 5 to 10 inches (locally more) of precipitation forecast during the next week, drought removal is most likely across extreme northwest California. Most large reservoirs throughout California remain at 25 to 50 percent of their historical average for this time of year. Although drought improvement is forecast for much of California, full recovery of large reservoirs is not anticipated. 
Forecast confidence for California is high.


El Nino favors an enhanced southern jet stream across the Southwest, which is expected to lead to either improvement or removal of existing drought. The CPC seasonal precipitation outlook indicates more than a 50 percent of above-average precipitation across southern Nevada and much of Arizona. Although the wet signal associated with El Nino decreases to the north across northern Nevada and northern Utah, a cold, wet pattern is likely during the remainder of December which increases chances for improvement. 
Forecast confidence for the Great Basin and desert Southwest is moderate to high.


A persistent wet pattern across the North Pacific and western North America resulted in flooding rainfall and heavy mountain snow across the Pacific Northwest during December. Much of the Pacific Northwest received above-average precipitation during the past 30 days, with the largest surpluses (more than 8 inches) observed across western parts of Oregon and Washington. Portland, Oregon received more than 10 inches of precipitation from December 1-15 which is 7.5 inches above normal. The latest storm on December 12-13 brought more than two feet of snow to the Oregon Cascades, above 4,000 feet. The abnormally wet pattern is likely to continue during the next two weeks across the Pacific Northwest. WPC 7-day precipitation forecast on December 16 indicates locally more than 10 inches of precipitation across southwest Oregon, while 8-14 day precipitation tools favor above-median precipitation throughout the Pacific Northwest. Drought removal is likely for southwest Oregon due to the anomalously wet December.  Improvement across eastern Oregon is based on the wet December pattern but forecast confidence is reduced as the CPC seasonal precipitation outlook favors below-median precipitation for this region. Persistence is expected across eastern Washington where precipitation surpluses are lower during the past 30 days and heavy precipitation is less likely during the next week. 
Forecast confidence is high for southwest Oregon and low for eastern parts of Oregon and Washington.


Idaho is a challenge due to the balance of weighing a wet December with an anticipated dry signal during JFM. As of December 8, basin average snow water content (SWE) is generally 100 to 150 percent of average across southwest Idaho. A persistent trough over the western U.S. is likely to bring additional rain and high-elevation snow to Idaho during the next one to two weeks. The most likely area for improvement or removal is southwest Idaho due to the current SWEs and heavier precipitation during the next two weeks. Persistence is expected across eastern Idaho where the highest probabilities of below-median precipitation exist in the CPC JFM precipitation outlook. 
Forecast confidence for Idaho is low.


Persistence and development forecast across Montana and North Dakota is based largely on the increased chances of below-median precipitation and above-normal temperatures forecast during JFM. Also, precipitation has generally averaged near normal during the past few weeks, unlike the anomalously wet Pacific Northwest.  
Forecast confidence for Montana and North Dakota is moderate.


The heaviest precipitation during the past 30 days was centered west of the lingering short-term D1 areas across lower Michigan and Indiana. During the remainder of December, a wet pattern is likely across these D1 areas, downstream of the amplified trough over the western U.S. Therefore, drought removal is likely by the New Year. Although below-median precipitation is favored during JFM which is consistent with El Nino, chances for drought returning to the Midwest by the end of March is considered low. 
Forecast confidence for lower Michigan and Indiana is high.


Long-term drought continues from northern New Jersey north to New England. Since precipitation tools on all time scales favor above-median precipitation across these areas, drought removal is expected during the next 3.5 months. 
Forecast confidence for the Northeast is high.


El Nino events are typically associated with a suppressed rainy season across Hawaii. This is especially true of a strong El Nino, as the associated enhanced convection is usually displaced from the central Pacific to the eastern Pacific. CPC's seasonal rainfall outlook for JFM 2016 depicts elevated odds of below-median rainfall for Hawaii. Therefore, drought development is expected.
Forecast confidence for Hawaii is high.


During El Nino winters, there is a tendency for wetness across Puerto Rico. The main uncertainty is whether or not above-median rainfall is enough to improve drought conditions by a full category. Similar to the previous month, a broad 1-category improvement is expected across Puerto Rico. Areas currently in severe to extreme drought (D2-D3) are expected to improve to moderate or severe drought (D1-D2), and areas currently in moderate drought (D1) are expected to be removed. 
Forecast confidence for Puerto Rico is low.

Forecaster: Brad Pugh

Next Seasonal Drought Outlook issued: January 21, 2016 at 8:30 AM EST