NWT Water Monitoring Bulletin – June 28, 2023 (Mackenzie Mountains Rainfall Forecast)

News Type: 
Water monitoring bulletin

YELLOWKNIFE (JUNE 28, 2023) — Environment and Climate Change Canada (ECCC) has issued a Yellow Weather Notification regarding a storm system expected in the southern part of the Mackenzie Mountains between June 29 and July 3.

This water monitoring bulletin interprets what this could mean for rivers and people in the NWT.

The situation

There is high confidence there will be two 24 hour periods with at least 50mm of rainfall over this period.

There is also the potential of over 150mm of rain falling within a single 24 hour period within the above date range. The heaviest rain is predicted to fall on Friday June 30 and Saturday July 1

Overall, there is moderate-high confidence that the highest rainfall will range from 100-150 mm over the course of 2-3 days over higher terrain in the southern Mackenzie Mountains.

There is less confidence on where precisely the heaviest rainfall will occur within the southern Mackenzie Mountains – however, forecasts suggest Wrigley and the South Nahanni River Basin could see very significant rainfall.

When compared to historic data for the general area, this means that 1-2 months worth of rain for this time of year could potentially fall within a matter of days.

Why it matters

This could impact people on the land. Rivers flowing into the Mackenzie River from the Mackenzie Mountains – such as the Redstone River, Keele River and Mountain River – are strongly affected by rainfall in the Mackenzie Mountains. This level of rainfall could mean rapid rises in water levels and flow along these rivers. 

Further, if heavy rainfall does fall within the South Nahanni Basin as forecast, there is the possibility of rapid rises in water levels and flow on the South Nahanni River and in the community of Nahanni Butte.

This level of rainfall in a short period also has the potential to cause challenges for infrastructure like roads and drainage systems.

What to do

  • The community of Nahanni Butte should be aware of this system, monitor conditions closely, and assess any risks to their community based on those conditions.
  • Those planning to be out on-the-land over the long weekend should be aware that this storm system may cause rapid rises in water levels and flow. Be prepared with communication methods before you go out on-the-land, know the conditions, and be prepared to leave your cabin, camp, or cabin on short notice should flooding become imminent.
  • In all flood-prone communities, including Nahanni Butte, it is always important for individuals to be ready for emergencies. That means having an emergency plan for you and your household, having an emergency kit ready to go, staying up-to-date with the latest information from your community, and following instructions from local officials should the time come.

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