Precipitation and Temperature: December precipitation ranks were between average and record wettest in Arizona, and between record driest and much above average in New Mexico (Fig. 1a). December temperature ranks were between above average and record warmest in both Arizona and New Mexico (Fig. 1b).
Annual/Seasonal Precipitation and Temperature: Annual precipitation ranks were between below average and above average in most of Arizona, and between much below average and average in most of New Mexico (Fig. 2a). 2021 temperature ranks were generally much above average across the western U.S. (Fig. 2b). Three-month Oct-Dec precipitation ranks are on a gradient that transitions from much below normal to much above normal with pockets of record wettest, as you move from southeast to northwest, in the U.S. Southwest (Fig. 3).
Drought: The U.S. Drought Monitor (USDM) showed widespread reductions in drought categorizations, but drought conditions are still found across the western United States (Fig. 4). A move out of “extreme” and “exceptional” drought (D3 and D4) is an improvement. Some regional categorizations remain in the “severe” (D2) or “moderate” (D1) drought categories, although, notably, much of Arizona has moved out of official drought and into “abnormally dry” (D0).
Snowpack & Streamflow: As of Dec 31, snow water equivalent (SWE) has increased across the Southwest (Fig. 5), and the Jan 1 streamflow forecast paints a relatively optimistic picture for much of the Colorado River basin (less so the Rio Grande) (Fig. 6). These normally peak around Mar 1 in the Southwest, so this is an important metric to track regarding the impact of La Niña this winter.
Water Supply: As of Jan 1, most of the reservoirs in Arizona and New Mexico are at or below the values recorded at this time last year, and nearly all of them are below their long-term average (see reservoir storage for Arizona and New Mexico).
ENSO Tracker: ENSO is at La Niña status, based on observed and forecast SSTs, emergent atmospheric conditions, and oceanic/atmospheric coupling indicative of La Niña. ENSO outlooks and forecasts generally call for a weak-to-moderate event to persist this winter with a transition to ENSO-neutral by spring or early summer (see ENSO-tracker for details).