VICTORIA (CP) - The Pineapple Express barrelled through southern British Columbia Monday, bringing rainfall higher than has ever been recorded. The deluge caused at least one river to spill its banks and about a dozen homes along the Chilliwack River were evacuated.
"I think that only in a province like B.C. can we go from drought to flood over the course of a week," said Allan Chapman, the head of the Environment Ministry's river forecast centre.
"We've been measuring very high rates of rainfall, in fact, probably some of the highest rainfall we've ever measured at a number of sites throughout the south coast."
An intense frontal system slammed the area shortly after nightfall Sunday, swelling coastal rivers already brimming after several days of heavy rain.
The Pineapple Express is a subtropical jet stream that brings warm, moist air from the south Pacific Ocean to the West Coast. But the term has also come to be used to describe the intense rainstorms that sweep in from the ocean in the early fall and winter.
Temperatures soared to 15 C in Vancouver on Monday.
Such storms can pose a two-pronged threat to coastal British Columbia since precipitation falls as rain instead of snow in the mountains, increasing the runoff into the local rivers, while it also melts the snow lying at lower altitudes, adding even more water to swollen stream and river beds.
Some areas had seen 200 to 350 millimetres of rain since Thursday afternoon, Chapman said from the headquarters of the Provincial Emergency Program.
The Nooksack River in Washington state was expected to reach flood level later in the afternoon, sending water over the border.
Chapman said it was difficult to accurately predict the flood pattern of other area rivers.
"The rainfall magnitudes we're receiving . . . . are amongst the highest we've ever recorded, so it goes a little bit beyond our record of understanding of these rivers," he said.
Larger rivers flowing into Howe Sound, such as the Squamish and Cheakamus, were not of major concern, but Chapman said high flows were being seen in smaller rivers in the Squamish-Whistler-Pemberton corridor.
On Vancouver Island, Chapman said, officials were seeing high flows on the Cowichan, Chemainus and Englishman rivers.
Notice of expected heavy rainfall went out to local governments and emergency agencies last Thursday and Friday.
"What was forecast is actually coming to fruition (and) local governments have been in the loop on this for quite some time," said Jim Whyte, the emergency program director in Victoria.
