La Niña continues to strengthen, as indicated by well-below-average sea surface temperatures in the equatorial Pacific Ocean extending from the International Date Line to the South American coast. If strengthening continues, this could become the strongest La Niña since the 2010-11 event that coincided with the historic drought covering Texas and other parts of the South Central United States. Already in the autumn, drought expanded to encompass approximately one-half of the contiguous United States — the greatest coverage in more than seven years. Currently, the most widespread and significant drought stretches from the Pacific Coast to the High Plains, with adverse impacts on water supplies as well as rangeland, pastures and winter wheat.
The winter (December 2020-February 2021) outlook from the National Weather Service indicates the likelihood of warmer-and drier-than-normal weather across the nation’s southern tier, especially in the Gulf Coast region and from Southern California to the southern portion of the High Plains. In contrast, colder- and wetter-than-normal winter conditions may occur from the Pacific Northwest into the upper Midwest. Wet weather may also affect areas from the Ohio Valley into the lower Great Lakes region. Given the already significant drought in place across the Southwest, a warm, dry winter could result in insufficient high-elevation snowfall leading to water-supply shortages in 2021. Farther north, however, La Niña-driven storminess may provide abundant snowfall in the Cascades and northern Rockies, helping to fill Northwestern reservoirs next spring.