It would only take a couple of hefty snowstorms in the next six weeks to set Northern New Mexico up for a better spring, according to a state snow surveyor.

But the trend right now is toward a continued warm, dry spell in the Southwest due to La Niña, the weather pattern caused by cooler-than-usual temperatures in the oceans around the equatorial Pacific.

Meanwhile, the latest U.S. Drought Monitor map from Jan. 31 shows more than 60 percent of the state, including Santa Fe, in severe to extreme drought.

Wayne Sleep, New Mexico snow surveyor for the federal Natural Resources Conservation Service, said both the snowpack and latest forecasted water supply through July is better than last year at this time. "We're ahead of where we were last year at this time, but [a dry winter] would compound what happened last year," Sleep said.

A poor spring runoff from the mountains into the reservoirs last year left little water after the irrigation season as a backup. "We have nothing to fall back on," Sleep said. "I would say for water users to be prepared for a low runoff year."

Historically, February and the first two weeks of March have been some of the best in terms of new snow for New Mexico mountains. Snowpack on those mountains -- from the Sangre de Cristos and Jemez in the north to the Gila in the south -- are critical for good river flows through the summer.

"The potential is still there to catch up," Sleep said. "If we can get a split jet stream or a dip in the jet stream like [what] happened in December, we could still get heavy, wet snow. It wouldn't take much to catch up."

Water supply is estimated based on the amount of snowpack at upper elevations and how fast the snow is expected to melt off. Higher daytime and nighttime temperatures, like those seen in January, or high winds, like those seen in northeastern New Mexico recently, can melt the snow quickly.

Water managers measure river health at several gauges. The most recent water-supply forecast this week predicts Rio Grande flows past the Otowi Gauge, between Pojoaque and Santa Fe, from March to July at 79 percent of the 30-year average compared to 76 percent this time last year. The average flow is 757,000 acre-feet.

Water inflow on the Rio Grande at San Marcial near Elephant Butte Reservoir is estimated at 70 percent.

If the snow continues to skirt New Mexico, "those numbers will continue to decline," Sleep said.

The snowpack in the Rio Grande Basin currently is about 85 percent of the 30-year average. The Canadian Basin is at 96 percent, and the Pecos, on the eastern side of the Sangre de Cristo Mountains, is at 93 percent.

Southern New Mexico is faring better than usual. The Mimbres Basin has a snowpack at 146 percent of average, while the upper Gila and San Francisco Mountains are at 99 percent.

The official weather prediction for New Mexico for February and March, from the National Oceanic and Atmospheric Administration, is for continued dry weather, especially in southern parts of the state.

Elephant Butte Reservoir was at 13 percent available capacity by Dec. 31, 2011. Navajo Lake was at 77 percent, and Heron Lake was less than 60 percent, according to the Climate Assessment of the Southwest out of the University of Arizona.

Contact Staci Matlock at 986-3055 or smatlock@sfnewmexican.com.