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Note: This work is published by the Climate Assessment for the Southwest (CLIMAS) project, The University of Arizona Cooperative Extension, and the State Climate Office at Arizona State University; and is funded by CLIMAS, and the Institute for the Study of Planet Earth.

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Forecasts and Outlooks > Archive
Southwest Climate Outlook - March 2009

Date issued: March 24, 2009

A. Summary

Drought– Above-average precipitation in December–February helped improve short-term drought conditions across northwestern Arizona. In New Mexico, drought conditions worsened with 55 percent of the state experiencing some level of drought.

Temperature– The past 30 days have brought warmer-than-average temperatures. Most of Arizona and nearly all of New Mexico have been 2–8 degrees F warmer than average.

Precipitation– In the past 30 days, most of Arizona and New Mexico has had less than 50 percent of average precipitation, with areas receiving less than 25 percent of average.

ENSO– The weak La Niña event that developed in December 2008 appears to be winding down.

Snow– Above-average temperatures and below-average precipitation over the past 30 days has led to a dramatic reduction in snowpack levels across much of Arizona and New Mexico.

Climate Forecasts– Long-lead temperature forecasts show increasing chances that spring and summer temperatures in the Southwest will be similar to the warmest 10 years of the 1971–2000 period. Summer precipitation has higher chances of being similar to the wettest 10 years.

The Bottom Line– A warm and dry February has led to a dramatic reduction in snowpack. Arizona has experienced above-average precipitation since December, helping to improve short-term drought conditions across the northwestern part of the state. In New Mexico, drought conditions are worsening. While snowpack in Arizona and New Mexico are well below average, most snow monitoring stations in Colorado measure near-average or slightly below-average snow water content.

Melting Snow Warm and dry conditions in the past month have contributed to the rapid melting of Arizona snow. On March 15, the water content contained in the mountain snows in the state averaged 86 percent of the 30-year average; streamflow forecasts continue to decline. Below-average snow water content (SWC) at the beginning of April is likely this year in Arizona, continuing a declining trend that has been evident in most of the western states since 1950. Although many people have speculated that human actions are the cause, only recently has scientific research helped attribute the decreasing SWC to greenhouse gases (GHG) and other human activities. A paper published in December 2008 in the Journal of Climate found that approximately half of the observed changes in snowpack over the western U.S. during 1950–1999 are caused by anthropogenic GHGs, ozone, and aerosols. Reducing spring snowpack is likely to continue and even accelerate, according to the paper’s authors, Pierce et al.

This month's cover photo Source: USDA Forest Service The Hog Fire burned a 16,802 acres in the Peloncillo Mountains on the Coronado National Forest near Douglas, Arizona. It began around March 2 and burned in grass, oak, and juniper terrain. The fire was human-caused.