High waves due to the strong winds in Gimli.

Colorado Low Slams Southern Manitoba Over May Long Weekend

Southern Manitoba was slammed by a powerful Colorado Low this past weekend that brought a wide array of severe weather to the province. Between heavy rain, ice pellets, snow and very strong winds, the storm wreaked havoc on the regions infrastructure with widespread damage to trees, power outages, closed highways, structural damage and overland flooding.

The system was, fortunately, well forecast by Environment Canada with fairly accurate forecasts issued in the days leading up to it alongside special weather statements addressing the numerous impacts the system may have on the region.

Significant Rainfall Began Saturday Afternoon

Fortunately, the weather was able to hold for much of Saturday. Temperatures climbed into the low 20’s across Southern Manitoba with increasing cloudiness. Rain & thunderstorms developed through North Dakota & Montana and lifted northwards through the day, first spreading into SW Manitoba in the afternoon and then eastwards and northwards through the evening and overnight period.

Some of the hardest hit regions were in SW Manitoba where hours of training thunderstorms & convective showers produced moderate to heavy rain. The Melita region was hit the hardest with 72mm of the grand total 90mm of rain falling by midnight on Saturday night. For areas further east, through, much of the rain fell through Saturday night & Sunday. Total rainfall amounts for Saturday and Sunday combined were:

Rainfall Totals for May 16–17, 2015 – Environment Canada & Manitoba Agriculture (*) Stations
LocationRainfall Total (mm)
Pilot Mound44
Winnipeg (Forks)41
Portage East*40
Portage Southport40
Oak Point37
Winnipeg Airport36
Great Falls34
Fisher Branch29
Cypress River28
St. Pierre*25
Berens River14

This rainfall is in addition to the 25–50mm of rain many areas in the region saw just a couple days prior to this storm. There were several areas that saw significant overland flooding due to the sheer quantity of water that fell over the short time frame.

Additionally, there were reports of sewage back-up and spotty basement flooding across Winnipeg.

Then Came the Wind

Sunday is where the brunt of the storm impact was felt. As the main low pressure centre lifted northwards into the Dakotas, a strong 1037mb high pressure centre was building into the central Prairies.

Surface analysis for early Sunday morning.
This surface analysis for early Sunday morning shows the strong low in the Dakotas and the strong high building into the central Prairies.

These systems produced a strong pressure gradient over southern Manitoba and produced some of the strongest, longest-duration winds for a major storm in recent memory. Winds were in excess of 50km/h for 20 hours in Winnipeg with a 6-hour stretch beginning late Sunday with winds of 60km/h or greater. Very strong gusts also accompanied the winds with Winnipeg recording the highest wind gust at 93km/h:

Peak Wind Gusts for May 17, 2015
LocationPeak Wind (km/h)Time (CDT)
Gimli Harbour899:38PM
Cypress River815:01PM
Pilot Mound812:45PM
Porgae la Prairie804:51PM

The winds may have been the most significant impact from this storm. The strong winds resulted in havoc on the highways, property damage, hundreds of downed trees, and widespread power outages. The strong winds also produced significant wave action on Lake Winnipeg and some overland flooding as rising lake levels resulted in the lake overspilling its banks and pushing inland in some locations.

Winds tapered off to 40 gusting 60km/h on Sunday night, but remained fairly strong until tapering off Monday afternoon.

Oh, Snow Too

If the rain and the wind wasn’t enough, cold air moving in with the high pressure system resulted in precipitation switching over to ice pellets then snow beginning over Parkland Manitoba and then spreading southeastwards through the Interlake, Red River Valley & Whiteshell through the afternoon and evening. Areas through the Interlake southwestwards towards the Melita region saw the heaviest snow, with MacGregor reporting the highest amount of snow at 15cm. Amounts of 10–15cm were seen from Arnes, on the western shores of Lake Winnipeg, through Teulon, MacGregor, Treherne and down towards Boissevain:

Snowfall Totals for May 17–18, 2015 – EC Spotters & Social Media
LocationSnowfall Total (cm)
Hollow Water FN5
Albert Beach5

In Winnipeg, we saw just a few cm of snow on Friday evening and overnight. Flurries persisted through Monday but temperatures were warm enough to prevent any more accumulation.

All in all, this was certainly one of the most powerful storms Southern Manitoba has seen in a good long while. Perhaps the best thing that can be said is that at least it happened now and not a month earlier, where almost certainly it would have been a historic blizzard.

Spring Storm Marks A Return to Form

A storm system pushing through Southern Manitoba tonight will bring snow, rain and everything in between to Southern Manitoba tonight, marking a significant shift in the upper-level flow that will bring seasonal to above seasonal temperatures through the weekend and into next week.

7°C / +2°C
Increasing cloud. Rain beginning this evening. 10-15mm.

10°C / 0°C
Clearing in the afternoon; chance of showers.

11°C / 0°C
Mainly sunny. Chance of showers overnight.

First Significant Rain of the Year

Today will be a pleasant day; high temperatures will sit around 6 or 7°C this afternoon with mainly sunny skies giving way to increasing cloudiness this evening. Winds will begin to pick up this afternoon to around 30km/h. The big story, though, is the low pressure system that will track through tonight.

A major low pressure system will begin pushing into Southern Manitoba tonight. This system, marking the transition into a warmer weather pattern, will spread significant rain and snow through the province during the overnight hours. Things will start off in the afternoon through the Parkland region with snow spreading eastwards from Saskatchewan. As the system pushes towards the Interlake and Red River Valley, precipitation will extend southwards, primarily as rain and then push eastwards through the remainder of the night. Winds will also be fairly strong, with sustained winds around 30-40km/h and gusts up to 60km/h.

Multiple precipitation types will be coming into play again with this system. The primary rain-snow line, at this point, looks like it will sit 50-100km north of the Trans-Canada highway. This line is not set in stone, however, and will likely meander north and south as temperature profiles change and precipitation intensifies and subsides. Areas near the rain-snow line may see precipitation flip from one to the other multiple times. With this low pressure system freezing rain is not expected, but ice pellets or a rain/snow mix are entirely possible.

Expected precipitation types for tonight's storm system.
Expected precipitation types for tonight’s storm system.

Precipitation, while relatively short-lived, will be fairly intense with this system. The heaviest axis of precipitation looks to extend from Parkland Manitoba, through the southern Interlake and northern Red River Valley and then through SE Manitoba into NW Ontario. For those on the snow side of the rain/snow line in Parkland Manitoba (including Dauphin), snowfall amounts will peak at around 10-20cm with amounts tapering off towards the northern Interlake and the rain/snow line. For the areas that will see rain, amounts will be split into three main groups:

LocationRainfall Amount
Extreme SW Manitoba (Melita)<= 5mm
SW Manitoba & Southern RRV5-10mm
Winnipeg/Northern RRV & SE Manitoba10-15mm

Saturday will start off mainly cloudy with mist and fog scattered through the Red River Valley. There will be a slight chance of showers, particularly through the northern half of the valley through Winnipeg and into the Southern Interlake. For any activity that does occur, however, amounts will be fairly minimal. Winds will be relatively light and skies will begin to clear for a sunnier afternoon. The temperature will top out around 10°C.

Saturday night will see temperatures dip to around 0°C with light winds. It’s likely that the substantial precipitation coupled with rapid snow melt and calm winds will produce fairly extensive fog through the Red River Valley. Fog is notoriously difficult to predict, so we’ll keep tabs on things into the evening hours and try to give as much heads up one way or another as to what to expect. Just be aware that for travel overnight Saturday into Sunday, fog may play into the picture.

Warmer Weather Arrives

We’ll start pushing into the significantly warmer weather on Sunday as another low pressure system approaches, bringing with it another pulse of warm air. Temperatures in Winnipeg will climb to around 11°C on Sunday with light winds under mainly sunny skies[1]. Temperatures on Sunday night will drop to around 0°C once again, but we do have an ever so slight chance of seeing some showers overnight as a disturbance tracks along the U.S. border.

Daytime highs should sit near to just above normal through much of next week, generally in the 10-15°C range. No threats for precipitation are expected until the second half of the week.

  1. If we end up with fog on Saturday night, we’ll see a cloudier Sunday morning, however skies should clear by late morning for a sunny afternoon.  ↩