With the first widespread rainfall event of the Spring season in the forecast for Thursday afternoon and Friday, municipal officials and area residents will be keeping a very close eye on on how much precipitation comes over the next two days.
"We have had substantial melting over the past four of five days, and indications are that Spring meltwater is now moving off the Manitoba Escarpment, and heading eastward through the Pembina and Red River Valleys," said CMOS Accredited Weathercaster Chris Sumner. "Municipal crews have been hard at work since last week's snowstorm reopening ditches, drains and culverts ahead of the water's arrival, doing all they can to help the water move through. The big question, heading into this rain event, is what impact will whatever amount of rainfall we receive will have on overland flooding risk."
Sumner added memories are still fresh from last year's overland flooding which impacted both rural and urban areas throughout the region, and the lessons learned from those experiences are certainly being applied right now to prepare as best as possible.
"A low pressure system moving northeastward through the U.S. plains is bringing the precipitation to our region," he explained. "The leading edge of that system will kick off periods of rain Thursday evening, and as the cold front moves through Friday, it will continue to generate shower activity. The rain, combined with temperatures remaining above freezing, will quicken the pace of the remaining snowpack melt. The rain, plus the melt water and the fact the frost isn't completely out of the ground means higher potential for runoff rather than infiltration, therefore the increased risk for overland flooding."
He noted there is still a fair amount of fluidity regarding where may see the most rainfall, and just how much that will be, but the general indication from the current forecast models is lower totals in Southwestern Manitoba, and then increasing eastward through the Red River Valley and Southeastern Manitoba. Sumner expects rainfall for the Valley and Southeast will land somewhere between 10 to 15mm, but there is the potential for higher localized totals.
"Because of the potential for this system to stall for a brief period of time Friday, we could see some training of showers, meaning heavier bands of precipitation moving over the same region over and over again," he said. "If that happens, and I stress it's an 'if', then we could see localized higher amounts."
The rain is expected to taper off by late Friday afternoon, with a cloudy start to the weekend Saturday, followed by a return to sunshine for Sunday and the start of next week. Temperatures will be below seasonal Thursday through Sunday, as the northwesterly flow behind this system pushes cooler air into the region. Averages for this time of year are 11 degrees daytime and -1 overnight.
"Looking ahead to next week, there are signs of upper level ridging for part of the week, meaning the Jet Stream is to our north and warm air from the south can flow into the region," Sumner said. "We could see double-digit highs by mid next week, landing in that 11 to 14 range."