A flood watch has been issued for the Fraser Valley as a "series of atmospheric rivers" hit southern British Columbia.The advisory applies to "Lower Fraser tributaries including the Chilliwack River, Skagit River, Coquihalla River and other areas of the Fraser Valley around Abbotsford, Chilliwack, Hope and east through Manning Park," as well as the Sumas River.."Observed rainfall since yesterday has been in the 20 to 45 mm range for the South Coast and Fraser Valley," the Ministry of Water, Land and Resource Stewardship wrote in a statement Tuesday. "The next period of heavy rain is anticipated overnight on Tuesday and through the day on Wednesday."Between 70 and 100 mm of rain is expected to fall in the Fraser Valley during that time.."The highest flows are currently expected around the Fraser Valley, including the Chilliwack River and surrounding areas," the ministry continued. "Current modelling is indicating the potential for flows to reach the 5-year to 10-year return period range or higher."Officials warned that "heavy rain and high streamflow bring increased risk for unstable banks, river erosion, submerged roads, swift water hazards, flooding and landslides.""Stay clear of the banks of swift running rivers and never drive across flooded roads, bridges or river crossings," they advised. "At this time of year leaves can clog storm drains and impact urban drainage. Keep storm drains clear."