A record amount of autumn rain and snowfall has raised fears of flooding throughout the region even before winter officially gets started.
“A rapid warm-up across northeast Washington and North Idaho would be a real disaster,” said Ken Holmes, who coordinates flood warnings from the National Weather Service in Spokane.
Inland Northwest snow depths range from a foot near Spokane to 4 or 5 feet in places like Pend Oreille County in northeast Washington and Bonner’s Ferry in North Idaho.
More than 6 feet is reported at ski areas.
Beneath the snow, the ground is saturated with water from rains that began in October.
Already, the wetlands south and west of Spokane are filled with as much water as they normally receive in late winter or early spring.
A quick thaw with heavy rains could unleash all the moisture in a torrent down streams and gullies.
“We could be looking at a lot of small-stream and urban flooding taking place,” Holmes said last week.
Last February’s flood occurred when heavy rain thawed the snowpack in the valleys and lower mountain elevations over a period of a couple of days.
If the trend continues, the fall-winter season of 1996-97 could be one of the wettest on record, said Eastern Washington University Geography Professor Bob Quinn, who studies long-range climate trends.
“We are certainly on a pace to be right up there with some of the all-time wettest winters on record,” he said.
Winter officially starts on Dec. 21.
This fall, Spokane set a record for precipitation in October and November, when 7.31 inches of rain and water from snow fell at Spokane International Airport.
That eclipses the previous October-November record of 7.25 inches set in 1882.
The last time more than 7 inches of precipitation fell in those same two months was in 1947.
The following May in 1948 saw some of the worst flooding on the Columbia River in modern times, but that occurred after an extremely wet spring.
Quinn said the Pacific Northwest could be moving into a wet cycle after years of intermittent drought in the late 1980s and early 1990s.
Weather records show that wet, snowy years are just as common in the Inland Northwest as dry years.
More than 30 inches of snow have been recorded so far at the Weather Service office on Rambo Road northwest of Airway Heights. The average for a winter season is 50 inches in Spokane.
Nearly 22 inches of precipitation has fallen in Spokane so far this year, putting the area on pace for the wettest year since 1948, when 26.07 inches was recorded. The average annual precipitation is 16.15 inches.
Quinn said the rain and snow are likely to cause flooding problems in rural areas around Spokane when a warm-up comes.
Residents should expect to see water over roadways, flooded fields and basements and a risk of contaminated drinking-water wells. Heavy runoff could cause washouts and field erosion, he said.
Holmes of the Weather Service is working with emergency managers in Eastern Washington and North Idaho to warn them if floods are imminent. Flood-potential watches are issued up to three days in advance.
Holmes said the biggest flood fears are for the Bonner’s Ferry area, where some residents report snow depths of nearly 5 feet.
Flood stage on the Kootenai River at Bonner’s Ferry has been 74 feet, but federal officials are expected to lower the official flood threshold to 70 feet because water levels above that have caused damage in the past, Holmes said.
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