Significant flood threat: tracking the next surge of water
Thursday, May 17, 2018, 7:54 PM - It's as if we’ve entered the eye of a hurricane (for flood season), as we’ve seen substantial decline in the flows since last week, but it’s a false sense of security, as there's high confidence in another peak in flows later this weekend
- Military is responding to the flooding emergency in B.C.
- Record warmth eases, but focus is now in precipitation amounts in southern B.C.
- Precipitation eases this weekend for the Interior, with just a spotty shower chance on Saturday and Sunday
- Warmth returns next week
Battling flood waters is extremely tricky, as the waters are combative, unrelenting, and often unpredictable. The flood waters will certainly test the peak flows recorded last week. The last flooding surge had two primary factors affecting flow rates: well above seasonal temperatures paired with significant rainfall — a disastrous combination, particularly for Grand Forks. Flow rates are also increasing in the Fraser River Basin, particularly upstream, and will begin to increase flows across all sections the Lower Mainland, with a peak forecast the next four or five days.
Most of the convective risk is forecast to ease on Friday, and by the weekend, just slight shower chances will remain. The River Forecast Centre has lowered their predictions slightly for this second surge, so that's excellent news, but the region is still vulnerable to significant flooding over the next couple of weeks.
Lake levels in Okangagan Lake are also nearing the full pool level, and about 90 cm below the 2017 peak. For more details on this, see the video at the top of the story.
After the thunderstorm risk diminishes, a weak trough hangs out over most of the province this weekend, effectively suppressing temperatures. But, it's short-lived, as another significant ridge is set to bring well above normal temperatures once again next week...the cycle continues.
Checking in on the snowpack, monitoring stations indicate that snowpack is fully depleted at the 1500 metre elevation in pockets throughout the Okanagan, but as little as 30%-40% for the highest elevations across the province. The River Forecast Centre releases flow forecasts for many rivers across the province, and gives insight into which rivers may approach flood stage by this weekend.