Drought Conditions

Source: U.S. Drought Monitor

Dry conditions have reigned in the last 30 days after a brief soggy period in late December and despite a small front moving through the region at the end of January. In January, nearly all of Arizona and New Mexico received less than 5 percent of the historical average. The scant recent rainfall has lowered total precipitation since the water year began on October 1, and many regions have received less than 75 percent of average precipitation since October 1 (Figure 1). Some areas have been particularly dry, including Roswell, New Mexico, where no rain has fallen in the last 90 days, and El Paso, Texas, which has only experienced one meager event in this period (Supplemental Figures 1–2). However, areas to the north such as Las Vegas, Nevada, and Cedar City, Utah, have been wetter than average, largely because of late December storms (Supplemental Figures 3–4). Also, most of the Upper Colorado River Basin has above-average snowpacks, which bodes well for producing above-average spring streamflows. This north-south precipitation divide suggests the brunt of the La Niña impacts will be felt in southern regions. Currently, 60 percent of Arizona and 95 percent of New Mexico have abnormally dry conditions or worse (Figure 2). The southern regions are the hardest hit by parched conditions. Severe drought conditions have developed in this area and now span about 11 and 4 percent of New Mexico and Arizona, respectively. The influence of the moderate to strong La Niña event so far this winter has upheld the historical pattern of below-average precipitation in the Southwest, and more dry weather is expected.

The La Niña event remains moderate to strong. Because a large pool of cold water continues to exist below the surface in the eastern tropical Pacific, forecasts indicate a 98 percent chance that La Niña will persist through March, and chances remain above 65 percent through May. As a result, drought forecasts call for continuing, expanding, and intensifying drought conditions in the southern half of Arizona and nearly all of New Mexico (Supplemental Figure 5).

Snowpack

Source: National Resources Conservation Service

• Above-average temperatures and below-average precipitation in the high country have contributed to below-average snow water content (SWC) in snowpacks (at left); SWC at many sites are below the 1971—2000 average (Supplemental Figures 6–10).
• Most snow telemetry stations in the Upper Colorado River Basin (not shown) measure above-average SWC; the upper Rio Grande basin has received near-average SWC.
• Early streamflow predictions call for above-average spring flows in the Upper Colorado River Basin; as of January 15, there was a 50 percent chance that inflow into Lake Powell will be 117 percent of average (Supplemental Figure 11).

Forecast