It’s not so much an El Niño but rather a positive Pacific Decadal Oscillation (PDO) identified as the culprit that’s triggered rapid snow melts.
Whatever you call it, the very warm temperatures and rain this winter have reduced the West Kootenay snow pack to 85 per cent of normal.
“The influence that has had more relevance this winter is the PDO,” says local forecaster Ron Lakeman.
Typically El Niño or El Niña, which refer to a southern oscillation of sea surface temperatures, come and go on a yearly basis, he told the Trail Times Thursday.
“But PDO refers to a 10-year span of monitoring the sea surface temperature of the Pacific Ocean off the coast of North America, including B.C.
“Those surface temperatures have been exceedingly mild this year, so the positive PDO phase has been the number one influence on our temperatures this winter.”
Normal highs in February are usually around 3 degrees (C), he continued, but the last few days temperatures have reached 8 C.
While rain is expected Friday, a cooling trend could hit the area by Sunday as a cold airmass across Alberta is predicted to flow into the West Kootenay region.
“There is potential for below freezing by Sunday night,” Lakeman noted. “And a few computer models are suggesting it could be cooler than normal toward the latter part of next week.”
While rapid snow melt in the valleys and at mid-elevations triggered flooding in the Nelson and Slocan area, higher up, it’s been winter as usual.
According to the Red Mountain Resort snow report, 60 centimetres (cm) of snow has fallen in the first two weeks of the month compared to the usual average of 34 cm.
“The snow pack prior to the recent rainfall event was generally at or below normal for the Columbia Basin,” explains BC Hydro’s Mary Anne Coules. “The total volumes are not expected to change much…although there is now more snow at higher elevations and less snow at lower elevations.”
The recent rainfall slightly increased local inflow to the Arrow Lakes Reservoir, but havesn’t resulted in changes to discharges at the Hugh Keenleyside Dam.
“Inflows and discharges from the Kootenay and Pend’Oreille systems, however, are currently above average for this time of year because of the recent weather,” she added.
Other than a few calls about minor runoffs onto West Trail properties, the City of Trail remains on stand-by should water at the Trail Creek intakes rise high enough to require intervention other than debris removal.
After tending to water rising in small drainage ditches and clearing the Trail Creek screens last weekend, the city’s excavator remains on site as a preventative measure.
Prior to spring runoff times, considered to be March 19, city staff reviews Trail’s Flood Contingency Preparation Plans, said Larry Abenante, City of Trail’s public works manager
“These plans are in place for any unforeseen flooding event in our higher risk areas.”
Twenty-one creek intake channels throughout the city are monitored in addition to Gorge Creek, at Palyga Drive and Ravine Street; and Trail Creek at Perdue Street and McQuarrie Creek, which are identified as high risk.
“Currently all channels are in good shape, however monitoring will continue and the intake screens kept clean as required,” Abenante added.
Additionally, public works has up to 600 full sandbags ready to go, as well as no-post guard rails and concrete blocks in inventory. So far, no problems have been reported with Beaver and Fruitvale Creeks running higher than normal.
“We are keeping an eye on them as we do during the normal freshet,” said Lila Cresswell, Fruitvale’s chief administrative officer. “No problems are anticipated as long as we don’t get a significant rain event.”
Besides gearing up the city’s flood watch, the area’s quick snow melt is perking up Trail streets earlier than usual.
“With these warmer temperatures, city crews have taken the opportunity to start cleaning up the winter sand around the city,” said Abenante.
Crews have already been out with the flusher truck to wash sidewalks down the Victoria Street corridor up to the Gulch area, and in front of city hall, the Trail Aquatic and Leisure Centre and other downtown sites and amenities.
“With this warm weather, we are a month ahead of schedule,” said Abenante. “We should be on the street next week with the sweeper, ready to clean up the grit.”