Record snowpack may bring record floods

BY PJ HELLER | BOISE, Idaho | March 1, 1999


Near record and record high snowfall throughout parts of the Pacific Northwest and the West -- some the highest levels in 25 years -- could

portend heavy flooding once temperatures start to warm up, weather experts warn.

"We know the potential is building with each snowstorm that crosses the state because we've got near record high snowpacks now," said Ron Abramovich, a water supply specialist in Boise with the Agriculture Department's Natural Resources Conservation Service. "We don't know the final outcome yet but people should be prepared."

Emergency management personnel in Idaho were scheduled to meet this week with local, state and federal agencies to discuss current

conditions and preparations for possible flooding, he reported.

The Natural Resources Conservation Service (NRCS) monitors snowpack in 12 western states via some 650 automated snow telemetry sites. Snow surveys in the U.S. began in the early 1900s on Mount Rose in Nevada.

"Some of the snow sites are the highest in 25 years," Abramovich reported.

One area in Washington was nearly 300 percent above normal while other areas in the state were 200 percent above normal. Idaho was at 160 percent of normal. The entire Sierra Nevada averaged 115 percent of normal.

Snowpacks were also reported well ahead of seasonal averages in western Montana, parts of Wyoming and the Lake Tahoe area. Elsewhere, the snowpack was reported near average in Colorado, Utah, and eastern Nevada.

"While the individual basins vary significantly from last year's readings, the statewide (Colorado) snowpack is right at 100 percent of last year at this time (the end of January)," said Stephen Black, state conservationist with the NRCS.

Central Arizona and New Mexico have virtually no snowpack. Only northern New Mexico (Rio Grande Basin) reported some snowpack, but

the amounts were still significantly below the seasonal average.

At the Mt. Baker ski area in Glacier, Wash., however, more than 70 feet had fallen as of Saturday (Feb. 27), which ski area officials said was

more than at any other North American ski resort in recorded history. The ski area was forced to close for two days in late February when

the snow rose to the chairlift seats.

The average annual snowfall at Mt. Baker is a little over 51 feet.

Abramovich said the unusually heavy snowfall in the Pacific Northwest was the result of La Nina, which he said was bringing moisture

across the Pacific West.

"So we're seeing a continuation of storms across this region," he said.

Other theories for the heavier than average snowfall include global warming, random weather patterns or a return to the types of winter

weather the area experienced in the past.

The heavy snowpack, meantime, is prompting concern about stream flow and possible flooding.

In Washington, where officials said a significant amount of snow was at elevations of 2,000 to 4,000 feet, "there is a concern about possible

flooding," said Scott Pattee, NRCS water supply specialist in Mt. Vernon, Wash.

"We would have to have lots of persistent rain and consistent warm temperatures," he added. "The danger is probably higher on the west

side of the state."

"We have the potential for some heavy runoff," Abramovich added. "We know that stream flow is going to be above average in the

northern two-thirds of Idaho. The part we don't know is how all this snow is going to melt."

A sudden warming trend or heavy springtime rains could exacerbate flooding with rivers and streams unable to handle the runoff. A slow

gradual warming trend would likely minimize or eliminate flooding.

In Clark Fork, Idaho, a $250,000 cleanup of the Lightning Creek has been under way by the U.S. Army Corps of Engineers so the waterway

can handle meltdown from a snowpack estimated at 200 percent of normal. The stream bed has been clogged with gravel and debris from

previous floods and residents feared that heavy runoff this spring could trigger flooding in the town.

Runoff from the snowpack throughout the West typically starts around April 1. At higher elevations, like the Tetons, the runoff normally

begins around May 1.

In January of each year, the NRCS begins forecasting stream flows. Those forecasts are further refined between Jan. 1 and April 1, based on current conditions and predictions from the National Weather Service, Abramovich said.

The Weather Service is predicting colder than normal temperatures and more snow in the coming months for the West Coast, which will

add to the already heavy snowpacks.

"What we do is analyze and digest this snowpack information and come up with our stream flow forecasts, what we expect April through

July," Abramovich explained. "We forecast the volume of runoff, whether it's going to be above normal or below normal, whether or not

there's going to be shortages during drought years or years like this with a surplus and a chance of high runoff occurring."


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