La Nina back say federal forecasters

On the heels of a wetter than usual January, La Nina is back to bring more of the same to the Pacific Northwest through the summer, reports the climate forecasters for the National Oceanic and Atmospheric Administration.

The first return of La Nina since the years 2000-2001 was announced last week at the American Meteorological Society's meeting in Atlanta.

La Nina forms with a slight cooling in parts of the Pacific Ocean along with changes in the jet stream. It usually results in wetter than average weather for the Pacific Northwest. The present weather phenomena could last through the summer, say forecasters.

And the wet weather in January is not being associated with the La Nina although scientists were predicting it up to three weeks ago based on changing surface temperatures in the Pacific.

The Libby area experienced 3.92 inches of precipitation in January, considerably above the 2-inch average for the month and well below the record of 6.92 inches set in 1953. And it bode well for mountain snowpack, which had been lagging behind historic averages after a dry November and December.

"On the first of February we should have about 60 percent of our seasonal snowpack in place and 40 percent of our main snowfall period remaining," said Roy Kaiser, Natural Resources Conservation Service water supply specialist for Montana. "So far, mountain snowpack is well above last year at this time."

According to Kaiser, Snowtel readings in the Kootenai drainage show the snowpack is 106 percent of average and 178 percent ahead of last year.

Statewide, mountain snowpack was 108 percent of average and 176 percent of last year. West of the Continental Divide, snowpack was 105 percent of average and 188 percent of last year and east of the Continental Divide, snowpack was 101 percent of average and 147 percent of last year. Valley temperatures across the state ranged from nine degrees above average in southwest Montana to 20 degrees above average in north central Montana.

"January continued the season's warm weather pattern, and several valley stations set record high temperatures," said Kaiser. "However, temperatures remained cool enough in the mountains to prevent the premature melting of mountain snowpack."

Assuming normal precipitation across Montana, streamflows are forecast to average 86 to 101 percent. West of the Continental Divide, streamflows are forecast to average 94 and 106 percent. East of the Continental Divide, streamflows are forecast to average 81 and 99 percent.

For the Kootenai, the streamflow forecast for April through July is at 93-103 percent of average. The forecast assumes near normal spring conditions and does not account for well below average (70 percent or less) or well above average (130 percent or more) snowmelt or spring rain.