Southwest Climate Outlook December 2020

Date issued

Monthly Precipitation and Temperature: November precipitation was average to below average across most of Arizona and New Mexico (Fig. 1a). November temperatures were above average to much above average in most of Arizona and New Mexico (Fig. 1b), with a pocket of record warm conditions in west Texas. The daily average temperature anomalies for Nov. 1 – Dec. 12 (Fig. 2) highlight the fluctuations at select stations around the region.

Fall 2020 Precipitation and Temperature: Total precipitation percentile for fall 2020 (Sept-Oct-Nov) ranged between below average and record driest in Arizona, and between average and record driest in New Mexico (Fig. 3a). Mean temperature for the same period (Sept-Oct-Nov 2020) was between above average and record warmest in most of the Southwest (Fig. 3b).

Drought: The Dec 8 U.S. Drought Monitor (USDM) expanded drought characterizations in the Southwest. Continuation of dry conditions (e.g. driest June-Nov period on record for AZ and second driest for NM) have led to continued degradation in drought conditions across the Southwest to the most intense category D4 across much of AZ and NM. Most of Arizona and over half of New Mexico is categorized as experiencing exceptional drought (D4) (Fig. 4).

Snowpack and Water Supply: The SnowView map from the University of Arizona shows the Snow Water Artificial Neural Network (SWANN) estimate of snow water equivalent (SWE) across Arizona and New Mexico as of Dec 12, 2020 (Fig. 5). The anomaly map (Fig. 6) highlights how station observations and basin estimates of SWE deviate from 1981-2010 median values. Many of the reservoirs in the region are at or above the values recorded at this time last year. Most are below their long-term average (see Arizona and New Mexico reservoir storage).

ENSO Tracker: La Niña conditions are present and are expected to continue through winter (see ENSO-tracker for details). If the region records below-average precipitation, as is forecast in most monthly and seasonal outlooks (see below), this does not bode well for drought conditions in the Southwest.

Precipitation and Temperature Forecast: The three-month outlook for Jan through Mar calls for increased chances for below-normal precipitation across the southwestern U.S. and northern Mexico (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across much of the southwestern U.S. and 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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