We suspect someone, somewhere is saying this right now, "Rain, rain go away, come again another day!" Yes, that Rainfall Warning remains in effect for much of Southern Manitoba with 50 to 60mm of precipitation possible Friday through Saturday morning before the system responsible moves out of our area.
"This will be an absolute soaker for those regions currently under a warning," noted CMOS Accredited Weathercaster Chris Sumner. "The upper level low pressure system bringing all of this moisture to the region is now slowly making its way northward out of the Dakotas, into Southern Manitoba and ultimately the central part of the province. The rain started during the early morning hours of Friday, and now that it's here, it will be with us for the next 24 to 36 hours until it tapers off Saturday morning into early Saturday afternoon."
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Sumner noted within the low there will be waves of rainfall of varying intensity, so it won't necessarily be heavy downpours all day.
"There may be periods where the rainfall is more like a light shower than a heavy rain, but with how long this system will be with us, the end result will be the same," he added. "We can count on significant rainfall totals by the time this event wraps up tomorrow."
And when exactly the rain will diminish is still somewhat of an x-factor, according to Sumner.
"High pressure over Hudson Bay is somewhat impeding this system's progress northward, and ultimately out of the Southern Manitoba region," he explained. "Depending on how the two systems interact, and just how much headway the low can make, that will dictate when the taps will turn off here."
At this point, Sumner is quite confident that by the late morning to early afternoon timeframe, at the latest, regions of the Red River and Pembina Valley's near the U.S. border will have seen the end of the precipitation, with cloudy conditions for the remainder of Saturday.
The other part of today's weather story are the strong northerly winds expected to develop, with the strongest expected Friday evening, potentially gusting up to 70 km/h as the low moves through the Red River Valley northward. The winds will diminish, somewhat, overnight and shift westerly Saturday around 30 km/h.
Meanwhile, temperatures will be well below average Friday and Saturday, as the northerly flow from the low pressure system brings a much colder than usual airmass into the region. Highs Friday will range from 7 to 9 degrees, with a little bit of recovery Saturday, possibly into the low double digits between 11 and 13.
"With the return to sunnier conditions Sunday, we'll see even further daytime high recovery, hopefully landing between 18 and 20 degrees," said Sumner. "The general trend in the long range forecast models for the final week of May is for seasonal to above average temperatures, but there are also signs of one more rainfall event. A somewhat weak disturbance moving through the area Sunday night into Monday could bring another few millimeters of rain, but we'll see how that plays out in the aftermath of the current system."