Southwest Climate Outlook April 2021

Date issued

Precipitation and Temperature: March precipitation was average to below average in most of Arizona and below average to above average in most of New Mexico (Fig. 1a). March temperatures were average in most of Arizona and between average and below average in New Mexico (Fig. 1b, SW Temps). Jan-Mar precipitation ranks were average to below average across most of the Southwest, with a few pockets of above-average (Fig. 2a). Temperature ranks for the same period were average to below average across most of Arizona and New Mexico (Fig. 2b).

Drought: Water year precipitation to date (as of Mar 31, 2021) reveals below normal and much below normal conditions across most of the Southwest, along with a smattering of record driest in the CA/NV/AZ region (Fig. 3). The U.S. Drought Monitor (USDM) is mostly unchanged from last month in the U.S. Southwest (Fig. 4). This is partly because much of the region is at the highest drought category (D4, Exceptional Drought) and the scale simply does not go any drier. In Arizona and New Mexico, over 50-percent of the region is in D4, and 80-85 percent is in at least D3 (Extreme Drought).

Snowpack and Water Supply: Snow water equivalent (SWE) is well below the 1981-2010 median for much of the region (see the NRCS website for details). Streamflow forecasts reflect this reality and are below median across the Southwest, and are below fifty percent of the median in many of the sub-basins for the Colorado and Rio Grande rivers (Fig. 5). Most of the reservoirs in the region are at or below the values recorded at this time last year. Most are below their long-term average (see Arizona and New Mexico reservoir storage).

Wildfire: Wildfire season is already underway in Arizona. The Margo fire burned Tamarisk (Salt Cedar) in a dry riverbed in central Arizona, as well as numerous structures in Dudleyville, AZ. The National Interagency Fire Center (NIFC) maps of significant fire potential for April and May highlight the widespread area of above-normal wildfire risk across the southwestern region over the next few months (Fig. 6).

ENSO Tracker: La Niña conditions have waned and outlooks and forecasts see ENSO-neutral conditions as imminent (or already arrived; see ENSO-tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for May through July calls for increased chances for below-normal precipitation across most of the southwestern U.S., with a swath of increased chances of above-normal precipitation extending from central Mexico into southwestern and far western Arizona (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across the southwestern U.S. and much of northern Mexico (Fig. 7, bottom).

Published by the Climate Assessment for the Southwest (CLIMAS), with support from University of Arizona Cooperative Extension, the Arizona State Climate Office, and the New Mexico State Climate office.

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