A weather system expected over southern Ontario this weekend could result in runoff and ice jams for local waterways.
We're expecting warm temperatures, rainfall and high winds before temperatures drop back below freezing late Sunday.
A Watershed Conditions Statement for Water Safety has been issued for the Maitland and Nine Mile River watersheds, along with the Grand River watershed.
A high of 4 C is expected on Saturday with temperatures remaining just above zero overnight into Sunday. The temperature is expected to reach 8 C on Sunday before dropping sharply Sunday evening. There is also the potential for 5 mm to 15 mm of rain over the weekend.
The water content in the snowpack varies across the watershed from 30 mm to 60 mm. Most of the snowpack is expected to be depleted by Sunday evening. The ground is currently frozen across most of the watershed and as a result, the snowmelt and rain will run off quickly into watercourses.
Based on the current weather forecast major flooding is not expected at this time; however, flooding may occur in low-lying areas. Water levels in headwater streams (Lucknow, Harriston, Listowel) and smaller rivers are expected to peak Sunday evening. Water levels downstream in the larger rivers (Wingham, Benmiller) will experience high, fast flows into Wednesday.
Ice remains in floodplain areas from the melt that occurred in early February. As water levels rise there is the potential for this ice to be shifted causing the formation of localized ice jams. Ice jams may cause water levels to change quickly so municipal officials should monitor low-lying and flood-prone roads.
Many local waterways throughout the Grand River watershed are covered in ice right now creating the potential for ice jams
Grand Valley, West Montrose, and New Hamburg all face a heightened risk of ice jams during this event. Watershed residents are reminded to remain cautious as ice jams can form quickly and without warning.
The Grand River watershed could see up to 20 mm of rain, which could result in flooding in low lying areas but major flooding is not anticipated.
Closure of the low-level bridge in St. Jacobs may also be required with this event.
The public is reminded to exercise extreme caution and stay off all water bodies at this time. Ice cover, where it exists, will be weakened as a result of the warming trend. Banks adjacent to rivers and creeks are very slippery and, when combined with cold, fast-moving water, pose a serious hazard. Parents are encouraged to keep their children and pets away from all watercourses and off of frozen water bodies