Highlights:

• A warm weather system has moved into the region. The melting snow and rain will raise water levels on smaller watercourses as well as the Thames River itself.
• Water levels on the Thames River around London are expected to peak Saturday. The peak will then move downstream over the following few days.
• As the high water moves downstream, flooding of the low-lying areas adjacent to the river is expected.
• An ice jam currently in place at the mouth of the Thames at Lighthouse Cove creates additional risk of flooding.

Message:

A warm weather system has moved into the region over the last few days. Last night, most of the Thames River watershed saw less than 10 mm of rain. Forecasts are calling for less than 15 mm of additional rain spread over the next two days. Temperatures have been above freezing since Tuesday and are predicted to reach 10 to 12 °C today before falling back to near freezing overnight. Temperatures Saturday are only expected to be a few degrees above freezing.

While most of the snow is gone from the lower Thames River watershed in Chatham-Kent and Essex County, there is still snow in Middlesex and Elgin. There are also substantial amounts of snow in the upper Thames River watershed. A snow survey conducted by the Upper Thames River Conservation Authority (UTRCA) on Monday, January 5, measured approximately 50 mm of snow water equivalent in the snowpack across most of the upper watershed.

The recent high-water event that occurred in late December and early January, has left a small ice jam in place at the mouth of the Thames River at Lighthouse Cove. Cold temperatures had refrozen most of the river in the downstream areas. However, the warm temperatures are causing the river ice to melt again. As of this morning, the river still had ice from the mouth, upstream to the lower end of the city of Chatham.

The warm temperatures and rain over the last few days have caused the snow to melt and to release some of its water. In those areas that still had snow, that has caused water levels to rise on our smaller watercourses. This process will continue throughout the day with the warm temperatures.

As the Thames River gathers water, water levels on the river will rise. Based on current forecasts, the Thames River through London is expected to peak on Saturday. The high-water levels will then move downstream through the lower Thames over the following few days. As they do, they will flood the low-lying areas adjacent to the river from Delaware down to Thamesville. In the city of Chatham, the sidewalk along the river in the downtown is expected to flood over, as is Simcoe Lane under the 5th St. Bridge. Areas of potential flooding may be updated over the weekend once the river peaks in London. Water levels on the river should be expected to be elevated through next week.

The presence of the ice jam at the mouth of the Thames River at Lighthouse Cove adds additional uncertainty to any flood forecasts. The ice jam has degraded due to the warm temperatures and will continue to weaken in the coming days. While Lighthouse Cove has no record of flooding due to ice jams caused by such thin ice, it is still possible that the jam will remain in place, and be reinforced by upstream ice, causing some flooding in the community or further upstream. In the past, high flows combined with an ice jam have backup up water all the way into the city of Chatham to an elevation that the 6th St. Dam would need to be operated. The ice jam and flows coming from upstream will need to be monitored in the coming days

People should take extra caution and avoid the river, ditches, and streams. Any remaining ice on these watercourses should be considered unsafe. The combination of slippery banks, unstable ice conditions, and fast-moving cold water can be dangerous. Standing water can also present its own unseen hazards. Children, pets, and livestock should be kept away from the water. It is not safe to take shelter along riverbanks or in low lying areas that are prone to flooding.

Officials will continue to monitor the situation and update this advisory as necessary.

This message will be in effect until January 13th.

Contact: Jason Wintermute ([email protected])