Southwest Climate Outlook March 2021 - Climate Summary

March 22, 2021
Ben McMahan

Monthly Precipitation and Temperature: February precipitation was mostly below average to record driest in Arizona and near average across most of New Mexico (Fig. 1a). February temperatures ranged between average and above average in most of Arizona and between average and below average in most of New Mexico (Fig. 1b).

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Winter Precipitation and Temperature: Dec-Feb Precipitation ranks were average to below average across most of the Southwest, with a few pockets of much below average (Fig. 2a). Temperature ranks for the same period were average to above average across most of Arizona, and mostly average in New Mexico, with some pockets of both above and below average (Fig. 2b). Precipitation totals from stations around the region demonstrate the below normal precipitation conditions this winter (Fig. 3).

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Drought: Water year precipitation to date (as of Feb 28, 2021) reveals widespread below normal and much below normal conditions across the Southwest, along with a large cluster of record driest in the CA/NV/AZ region (Fig. 4). The U.S. Drought Monitor (USDM) is mostly unchanged over the last month in the U.S. Southwest (Fig. 5). This is partly because much of the region is at the highest drought category (D4, Exceptional Drought): In Arizona and New Mexico, over 50-percent of the region is in D4, and over 80-percent is in at least D3 (Extreme Drought).

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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 well below median across most of the Southwest (Fig. 6). 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).

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ENSO Tracker: La Niña conditions are present and are expected to continue through spring (see ENSO-tracker for details). Despite some winter storm activity (including some impressive snow totals), the expectation remains for cumulative cool season precipitation totals to be below average for much of the Southwest.

Precipitation and Temperature Forecast: The three-month outlook for Apr through Jun 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 southeastern Arizona (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across the southwestern U.S. and northern Mexico (Fig. 7, bottom).

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Online Resources

  • Figures 1, 2 - National Centers for Environmental Information - ncdc.noaa.gov/sotc
  • Figure 3 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 4 - West Wide Drought Tracker - wrcc.dri.edu/wwdt
  • Figure 5 - U.S. Drought Monitor - droughtmonitor.unl.edu
  • Figure 6 - National Resource Conservation Service - nrcs.usda.gov
  • Figure 7 - International Research Institute for Climate and Society - iri.columbia.edu