It is not a La Niña winter, but it feels like one. A high-pressure system has parked over the Southwest for nearly a month, creating dry conditions and above-average maximum temperatures. With the exception of one storm, which sneaked into the region on December 20 and dropped as much as 0.5 inches of precipitation in parts of the Southwest, clear conditions have prevailed. Rain and snowfall have totaled less than 25 percent of average in many parts of Arizona and New Mexico (Figure 1), creating precipitation deficits of more than an inch and half-inch in Arizona and New Mexico, respectively.
Drought conditions, however, have not changed much in the past month, according to the U.S. Drought Monitor. About 57 and 80 percent of Arizona and New Mexico, respectively, are experiencing at least moderate drought. A “half-full” interpretation of these numbers would cite an improvement of drought compared to one year ago, when nearly all of both states were classified with at least moderate drought and about 32 percent of New Mexico was experiencing extreme drought. The “half-empty” view would argue that drought conditions likely will expand in coming weeks due to the dry conditions, and would point to below-average snowpacks in Arizona and New Mexico (Figure 2).
The snowpack conditions, however, also bring a mixed interpretation. Above-average snowpacks in Colorado watersheds are a welcome sign for people with an eye on the water stored in Lakes Mead and Powell. Early streamflow projections call for near-average spring and summer streamflows (Figure 3), which would help prevent water elevations from dipping below the 1,075-feet above sea level (asl) threshold that initiates reductions in Colorado River water allocations to some users. Lake Mead is projected to end the 2014 water year (September 30, 2014) at 1,085 feet asl. On the Rio Grande, spring-summer streamflows are projected to be about 60 percent of average—feeding a grim forecast based in part on below-average snowpacks currently in the river’s Colorado headwaters. Moreover, there are signs that Colorado River water transfers to the Rio Chama, part of New Mexico’s Colorado River allocation, could be reduced this year, which would impact Albuquerque water users. It is still early in the winter, however, and a few storms can dramatically improve the Rio Grande’s outlook.
With ENSO-neutral conditions expected to persist, the jet stream likely will break free of the high-pressure vice currently in place and deliver rain and snow. The quantity of precipitation, however, may fall below the February–April average, according to the latest NOAA-Climate Prediction Center seasonal precipitation forecast.