A Couple More Cool Days Before We Heat Up

We’ll have a couple days of cool weather before an upper ridge builds in, bringing hot & humid weather to southern Manitoba in the second half of the week. The arrival of the heat and humidity is also expected to bring our first significant risk of severe thunderstorms this year.

A cool northerly flow will be in place over southern Manitoba on Monday
A cool northerly flow will be in place over southern Manitoba on Monday

This Week

Today will remain on the cool side as a surface high to our north-west pumps cool air into southern Manitoba. Some cloud cover is expected in southern Manitoba during the morning as an upper disturbance moves through, but skies should clear by the afternoon. Daytime highs will be in the upper teens with gusty north winds at 40 km/h gusting to 60 km/h.

Tuesday will remain cool as we remain under the influence of that surface high. Temperatures will once again be in the upper teens, although some areas in western Manitoba may reach the low twenties. Skies are expected to be mainly sunny and winds will be breezy from the north.

Warmer weather will begin to move into southern Manitoba on Wednesday as the surface high moves off to the east. A southerly flow will be in place over southern Manitoba, helping to bring warmer air into the region and push daytime highs into the mid twenties over the Red River Valley and the upper twenties over western Manitoba. There will likely be a risk of severe thunderstorms in eastern Saskatchewan on Wednesday and that may spill over into western Manitoba. Depending on how conditions develop, the thunderstorm risk may extend across all of southern Manitoba on Wednesday night as storms from Wednesday evening move east with time. A westerly steering flow and a strong southerly low-level jet would tend to favour easterly or south-easterly storm motions, which would help steer storms toward the Red River Valley during the overnight period. More details on Wednesday’s potential thunderstorm risk will be available as the week progresses.

Long Range

The long range forecast suggests a hot, but unsettled pattern, will be in place for southern Manitoba from late this week into the weekend. An upper ridge will be centred over southern Manitoba during this time period, but we are expected to remain at the top of this ridge, putting us along the storm track. The influx of warm, humid air due to the southerly flow in this ridge combined with the moderate to strong flow with the jet stream aloft should favour numerous thunderstorm chances during the Wednesday-Monday period. The nature of the thunderstorm threat remains quite unclear, but at least one or two severe events seems probable at this time. An upper trough is expected to approach either late this weekend or next week, which will push out this hot/humid air mass.

Wall Cloud near Clairevale

Winnipeg & Area’s Top 10 Weather Stories of 2015

2015 brought a huge assortment of wild weather to Southern Manitoba. From torrential rains, damaging wind storms, tornadoes, and above-normal temperatures to snow storms, there wasn’t much waiting between significant weather events. Here’s our top 10 weather stories of 2015!


#10 – Parade of Snowstorms Just Before Christmas

Three snowstorms dumped a total of 40 cm of snow from December 16th to 23rd in Winnipeg.

The biggest snowstorm occurred on the 16th and 17th, dumping 20 cm. Strong winds helped carve drifts up to two-feet deep in some spots. 18 cm fell on December 16th alone at the official Charleswood station, breaking the old record of 8.4 cm in 1942 for the day.

Snowfall totals from the December 22-23, 2015 Snow Storm
Snowfall totals from the December 22-23, 2015 snow storm

With all the snow in mid December, travel was dramatically impacted. Residential streets were difficult to navigate and numerous vehicles were reported stuck in the snow. Thanks to the snowfall, snow depth in Winnipeg sat at 30 cm on Christmas morning; this was the deepest snow pack on Christmas Day in 15 years (since a 30 cm depth in 2000). In total, 44.0 cm of snow fell in Winnipeg in December, 83% above normal and the 12th snowiest December on record since 1872.

#9 – Dry Winter and Warm January

After a frigid start to January, a warm spell blessed southern Manitoba with above normal temperatures. A 17-day streak of above normal temperatures occurred from January 14 to 30. During this period, daily highs averaged -1.9°C and daily lows averaged -12.1°C, about 10°C warmer than normal. 6 days in the period exceeded the freezing mark and 6 days never saw temperatures dip below -10°C. The warmest days were January 22 and 23 when temperatures soared to 3.7°C and 3.1°C at the airport respectively. It was warmer inside the city with highs between 4 and 6°C. Some parts of southern Manitoba never even dipped below freezing on January 23. The extended warm spell melted what little snow was on the ground. By January 31, snow depth in Winnipeg was 12 cm, the 12th thinnest on record for the day since 1941. Gloomy skies and freezing drizzle were also common during the warm spell.

In the end, January averaged -13.7°C, tied with 2010 for 19th warmest since 1873.

Overall, it was a very dry winter. Only about 31 mm of precipitation fell from December to February, the 9th driest winter on record since 1872. 44.4 cm of snow fell, the 29th least snowy winter.

#8 – A Summer of High Humidity

With an average dewpoint of 13.6°C (June to August), summer 2015 tied with 1996 for 4th most humid summer on record in Winnipeg since 1953. 22 days from June to August saw dewpoints exceed 20°C, the 2nd most since 1953 and well above the normal of 10 days.

Dewpoint temperatures in July specifically averaged 16.1°C, the 2nd most humid July and month on record since 1953. The 1981-2010 normal is 14.2°C. An 8-day streak with dewpoints over 20°C occurred mid month. A maximum dewpoint of 24.1°C was achieved on July 12, breaking the old record of 23.9°C in 1955 for the day. 14 days saw dewpoints over 20°C, tied with 1957 for most on record in July since 1953.

A 5-day heat wave hit southern Manitoba in mid August. Temperatures exceeded 30°C and on some days 32°C. August 14 was the hottest day with some records broken, including in Brandon with a high of 36.6°C. Four days with dewpoints over 20°C accompanied the heat wave. Dewpoint temperature peaked at 24.5°C in Winnipeg on August 15, shattering the old record of 21.7°C in 1972 for the day. It was also the latest occurrence of dewpoint over 24°C since 1953. High minimum temperature records were also broken in Winnipeg (21.2°C) and Morden (22.0°C).

#7 – Summer in September

September began with a three-day heat wave as temperatures exceeded 30°C and in some cases 32°C. Oppressive humidity accompanied the heat which is unusual for September. The main records broken during the heat wave are listed below. Note: temperature records go back to 1872 while dewpoint and humidex records go back to 1953.

  • Record high minimum of 21.0°C on the 3rd was also the second highest in September.
  • Two high dewpoint and three high minimum dewpoint records were broken, including:
    • High dewpoint of 23.1°C on the 3rd was also just shy of the all-time September high of 23.4°C in 1983 and was the second highest in September.
    • A high minimum dewpoint of 18.7°C on the 3rd was also an all-time high for September.
  • Humidex reached 42.0 on the 3rd, the second highest in September. This, along with a humidex value of 40.1 the previous day, were only two of six occurrences of humidex over 40 in September since 1953.

Strong thunderstorms on the 4th and 5th ended the heat wave with a bang. Severe storms between 1 and 8 am on the 4th dropped dime to toonie size hail southeast of Winnipeg and northwest of Minnedosa. Strong thunderstorms moved up the Red River Valley in the afternoon. The Winnipeg area saw 30 to 50 mm of rain in under an hour, causing severe street flooding. Wind gusts over 80 km/h also caused some damage. With more rain later on, daily totals sat between 40 and 60 mm. The airport recorded 41.1 mm, breaking the record of 36.8 mm in 1872. Heavy thunderstorms moved up the Red River Valley again on the 5th, dumping 15-40 mm of rain southeast of Winnipeg.

Another 30°C day occurred on September 13. Winnipeg reached 31.6°C, just shy of the record of 31.7°C in 1927. Records were broken along the US border including in Morden and Pilot Mound where highs of 33.8°C and 33.3°C occurred.

It was the 6th warmest September on record since 1872 in Winnipeg with an average mean temperature of 15.8°C. It was also the second warmest since 1949. Dewpoint temperatures averaged 9.8°C, the 3rd most humid September since 1953.

#6 – A Very Early Spring

April-like temperatures arrived by the second week of March. Record highs were achieved on the 14th and 15th. Winnipeg reached 13.2°C on March 14, breaking the old record of 11.4°C in 1981. A high of 14.3°C the following day was just shy of the record of 14.4°C in 2012. The warmest temperatures occurred along the US border. Morden reached 18.3°C on the 14th and 17.6°C on the 15th, the earliest occurrences of temperature over 16°C on record since 1904. The high of 18.3°C on March 14 broke the old 2012 record by an impressive 7.1°C! Nights were unusually mild as well. A morning low of 6.7⁰C in Winnipeg on March 15 was the warmest morning low for so early in the year since 1953.

The winter snow pack disappeared in Winnipeg by March 15, tied with 1995 for third earliest snow melt since 1955. This was a day later than in 2012 and a day earlier than in 2010.

In the end, March averaged -3.0°C, 2.8°C warmer than normal and the 20th warmest March since 1872. Even thunderstorms with small hail occurred on March 30 west and north of Winnipeg. No thunder was heard in Winnipeg but small hail fell in the south end with some convective showers.

#5 – Active Thunderstorm Season in Southern Manitoba

Manitoba had the greatest number of reported tornadoes and waterspouts in Canada for 2015. In addition, Manitoba had the most severe hail and severe thunderstorm rain reports of the three Prairie provinces.

At least 11 tornadoes and waterspouts occurred in Manitoba in 2015, the most in more than 5 years. Two events brought worldwide attention: at least 2 tornadoes and waterspouts on July 18 near Matlock and at least 3 tornadoes on July 27 in southwestern Manitoba(3 tornadoes were mentioned in Justin Hobson’s chase story).

On July 18, a landspout tornado near Matlock travelled over Lake Winnipeg, becoming a waterspout. The storm produced at least one other waterspout and they occurred simultaneously. The storm and funnels were photogenic and photos spread around the world on social media.

On July 27, a supercell travelled over 100 km from Tilston to northeast of Virden, producing multiple tornadoes in a 3-hour timeframe. Some were violent as seen on videos. One tornado reached about a kilometre wide. Luckily, the tornadoes dodged all major communities.

Only a few farms and highways experienced damage. Environment Canada sent a damage survey team to investigate. The worst damage they saw was from a high-end EF-2 tornado (winds close to 200 km/h). It is entirely possible that the tornadoes may have been even stronger, but because they weren’t hitting anything significant it is impossible to tell.

Hail was also a big story this summer across southern Manitoba. The greatest proportion of severe hail reports were in August thanks to extreme nocturnal activity mid and late month. Significant hail events occurred on August 12, 22 and 28.

Along with parts of southern Alberta, southern Manitoba had the greatest concentration of severe thunderstorm warning days as seen in the map below. The Minnedosa warning region of southwestern Manitoba saw 19 days in 2015 with a severe thunderstorm warning, the most of all warning regions in Canada.

#4 – May Long Weekend Storm

A Colorado Low slammed southern Manitoba during the May Long Weekend. Heavy rain, damaging wind, large waves on the lakes and snowfall occurred.

The rain in Winnipeg began late on Saturday May 16 and persisted the entire day on Sunday May 17. 35-50 mm fell in the city. 31.3 mm fell at Winnipeg airport on May 17 alone, breaking the old record of 22.9 mm in 1903 for the day. Heavier rains fell to the southwest with 50-90 mm from Morden to Carman to Melita. Significant overland flooding occurred with many farm fields underwater.

The rain was accompanied by sustained winds of 47 to 63 km/h at Winnipeg airport for 22 consecutive hours. Wind gusts were between 80 and 95 km/h. A peak gust of 93 km/h was recorded in Winnipeg. The wind damaged property, caused power outages and uprooted trees. In addition, larges waves and storm surge occurred on Lake Manitoba and Lake Winnipeg.

On Monday May 18, snow and strong wind occurred. Snow fell throughout the night, ending in the morning. The cold and wind combined to produce wind chill values of -9. Between a dusting and 3 cm of snow fell in Winnipeg, depending where you were. 2.5 cm was measured in Charleswood on May 18 alone, just shy of the old record of 3.0 cm in 1963. A snow depth of 2 cm in the morning observation broke the old record of trace cm. The snow melted in the afternoon. This was the latest spring snowfall in Winnipeg since 2002 when a trace cm fell on May 23 and the latest snowfall accumulation since 1969 when 0.3 cm fell on June 12. Prior to this year, snow had fallen on May 18 only 4 times since 1872. Heavier snow fell west of the city with a swath of 10-15 cm from Boissevain to McGregor to Teulon to the Gimli area.

#3 – August 22-23 Severe Thunderstorms and Heavy Rain

Significant thunderstorms and heavy rain pummelled Winnipeg and the surrounding area on August 22 and 23. Due to extreme nature of the event and the large area affected, the event is considered number three in the Top 10 series.

The event began overnight on August 22 when severe thunderstorms developed north of a warm front. The bulk of the storms remained north of Winnipeg, sparing the city from the worst of the event.

The city got a spectacular lightning show, while the cottage-country north of Winnipeg and a few towns northwest of the city took the brunt of the storms. Very large hail fell from Westbourne to Teulon to Matlock to Beaconia to Silver Falls. The largest hail stone reported was 10 cm in diameter, located near Silver Falls. Significant and widespread damage occurred as a result. Locally 40-50 or more mm of rain also fell within an hour, causing overland flooding. The following table gives a chronology of storm reports from the event.

Table: Chronology of storm reports from the overnight thunderstorms of August 22
Approx. Time Location Event
2:00 am Westbourne Nickel to golf ball size hail.
4:15 am Teulon Quarter size hail with significant accumulation. Tree, garden and vehicle damage occurred. 43 mm of rain in 1 hour caused overland flooding. Mounds of hail still remained on the ground hours after the storm.
4:45 am Matlock 5 cm diameter hail.
5:15 am Grand Marais Gold ball size hail.
5:30 am Beaconia Baseball size hail punched holes in roofs and totalled almost every vehicle left outside during the storm. 50+ mm of rain also fell within an hour.
5:45 am – 6:00 am Pine Falls, Powerview and Silver Falls area Nickel to softball size hail. One photo showed a 10 cm diameter hailstone.

Heavy thunderstorms developed again midday in the Red River Valley. Winnipeg was particularly hard hit by these. 50 mm fell in less than 1 hour in parts of the south end. Nickel to toonie size hail, wind gusts to 80 km/h and frequent lightning also occurred, making for quite a storm to remember. Numerous streets and underpasses flooded and some were impassable. Water seeped into and flooded parts of St Vital Mall. Lightning caused a few fires and wind snapped branches.

Rainfall totals from the August 22-23 Storms
Rainfall totals from the August 22-23 storms

The afternoon thunderstorms also dumped some large hail in other areas. Nickel to quarter size hail fell in Oakbank, Winkler and Jessica Lake. Training thunderstorms continued to pummel southeastern Manitoba late afternoon and evening, dumping significant rainfall. Rain from these also spread into the Winnipeg area and Red River Valley. Wrap-around rain around the low pressure system continued to drench south and southeastern Manitoba in the overnight and morning on August 23. Two-day rainfall totals were significant. Widespread totals of 50 to 110 mm occurred throughout the Red River Valley, southeastern Manitoba and the Interlake. In Winnipeg, close to 75 mm fell in southern sections of the city. At Winnipeg airport, about 46 mm fell. 38.4 mm of this fell on August 22 alone, breaking the old record of 38.1 mm in 1959 for the day.

#2 – Warm and Moist Fall

All three fall months (Sep, Oct & Nov) finished in the top 30 warmest on record since 1872 in Winnipeg: September was 6th warmest, October tied 30th warmest and November tied 16th warmest. It was the 4th warmest fall on record since 1872 with an average mean temperature of 7.3°C, tied with 1953 and 2009. Brandon also had a 4th warmest fall on record (since 1890), averaging 6.2°C.

In October, the warmth peaked during the Thanksgiving weekend. Record warmth was seen along the US border with highs near 28°C in Pilot Mound, Morden and Sprague. Winnipeg reached a non-record maximum of 24.6°C on the 11th. Even some weak thunderstorm activity occurred in the evening on the 11th, ahead of a strong low pressure system which produced damaging winds the following day.

A 25-consecutive day streak of above normal temperatures occurred from October 26 to November 19. During this time, 10-consecutive days from October 27 to November 5 never dropped below freezing. Warmth and humidity returned mid November before winter-like conditions arrived. Temperatures exceeded 10°C from the 14th to 16th with a maximum of 13.1°C on the 15th. Unusually high humidity also occurred with dewpoints reaching 9.4°C on the 16th and 9.3°C on the 17th, both record highs and the latest occurrences of dewpoint over 9°C on record since 1953. Thanks to the high humidity, a record high minimum temperature of 5.3°C was achieved on the 16th, the latest minimum above 5.0°C since 1872.

Dewpoint temperatures averaged 3.2°C in fall 2015, t he second most humid fall on record since 1953. November dewpoint temperatures in particular averaged -2.9°C, the highest on record, beating the old record of -3.0°C in 1981.

Thanks to warm conditions, the first accumulative snowfall was on November 18 in Charleswood, Winnipeg’s official station for snowfall. This was the 4th latest first snowfall accumulation of the season since 1872. It was also a month later than the normal of October 18. In addition, no snowfall was recorded in October, only the 16th time this has occurred since 1872.

#1 – Amazingly Warm Start to December

Remarkable warmth started December across southern Manitoba. 8 to 10 days in the first half of the month exceeded the freezing mark in Winnipeg, above the normal of 4 days for the month. 14-consecutive days from the 3rd to 16th never dropped below -9°C at Winnipeg airport, amazing when you consider this was close to the normal high. Temperatures reached 7°C downtown and 4°C at the airport on the 3rd, one of the warmest days of the month. The only record broken during the warm spell was on December 9 when a high of 5.6°C at the airport broke the old record of 5.1°C in 1990.

Morden, MB – Cutting grass in December.
December started with such warmth that the grass still needed to be cut in Morden, MB.

The warmth was most impressive where there was no snow cover. 3 to 7 cm of snow was leftover from November in the Winnipeg area and this limited temperature. Areas without snow cover southwest of the city and in southwestern Manitoba were much warmer. Many locations reached double digits and in some cases more than once. In Morden, four days exceeded 10°C, three of which were record highs. The high of 14.2°C on December 4 was the third warmest on record in December since 1904. Some thermometers reportedly reached 15°C, more typical of late September or early October. No snow was on the ground at the time. A similar milestone was reached in Brandon with a high of 11.1°C on the 4th, the third warmest temperature in December since 1890.

The first half of December (December 1 to 15) averaged -3.0°C at Winnipeg airport, the second warmest first half of December on record since 1872. The warmest was in 1913 with an average of -2.1°C. The month as a whole averaged -8.1°C, tied with 2011 for 9th warmest December since 1872.

Stormy Start to An Unsettled Weekend

Friday will bring a severe thunderstorm threat to Winnipeg & the Red River Valley as the first of several bouts of unsettled weather moves through, gradually flushing out the unseasonal heat and humidity and transitioning us towards almost fall-like weather.

Friday
29°C / 18°C
Mainly cloudy; showers and thunderstorms this afternoon

Saturday
24°C / 17°C
Mainly cloudy; slight chance of showers. Evening showers or thunderstorms possible

Sunday
24°C / 11°C
Mainly cloudy; slight chance of drizzle or light rain

Mainly cloudy skies will be over Winnipeg & the Red River Valley today while a low pressure system gather steam and begins to move into the region from North Dakota. Little in the way of weather is expected until the low approaches this afternoon and triggers a substantial amount of convective activity. Showers and thunderstorms are expected to fire up mid-afternoon and track to the northeast. There’s a decent chance that the stormy weather will persist well into the evening before it clears out and moves off to the northeast.

AWM Day 1 Convective Outlook
A slight risk of severe thunderstorms exists over south-central and southeastern Manitoba today.

A slight risk for severe thunderstorms will be in place over much of south-central and southeastern Manitoba today. Looking at the MIST basics for thunderstorms:

  • Moisture will be ample with deep boundary layer moisture evident through surface dewpoint values near 22°C thanks to a multi-day build-up of humidity in a southeasterly flow. Strong evidence of the substantial moisture in place is shown by the precipitable water values which are forecast to climb over 50mm through the afternoon.
  • Instability will moderate with MLCAPE values around 2000–2500 J/kg. Much of the instability will be brought through the substantial moisture present since mid-level lapse rates are only expected to be moderate and not excessively steep.
  • Shear will be ample with approximately 25–35kt of 0–6km bulk shear and broadly looping hodographs. This should support the development of organized thunderstorms.
  • Trigger: there will be several triggers converging on the Red River Valley this afternoon including a frontal boundary, approaching low, as well as shortwave aloft. There should be no troubles finding something to trigger thunderstorms.

The primary threats from today’s storms will be heavy rain and large hail. PWAT[1] values are expected to climb over 50mm, which means torrential downpours and flash flooding will be a notable threat with this afternoon’s thunderstorms. Additionally, with such high MLCAPEs and adequate storm structure through the shear profiles, large hail may be an issues, however that would likely be a more isolated threat than the rainfall.

The thunderstorms will gradually push off to the northeast. Total storm rainfalls may exceed 2–4” (50–100mm) in some places, while other areas may end up seeing very little. Be sure to stay alert for any watches or warnings issued by Environment Canada.

Less excitingly, daytime highs will sit around 29°C today (which will feel more like the upper 30’s thanks to the humidity) with winds out of the southeast at 20–30km/h. Expect a low near 18°C.

Cooler, Unsettled Weekend

Both Saturday and Sunday will be cooler days with highs in the mid–20’s. Some uncertainty exists on precisely how things will play out, but in general, a very powerful low pressure system is expected to develop and lift northwards through Saskatchewan through the weekend.

The biggest change, compared to Friday, will be that it seems like the timing for any precipitation will shift from daytime hours towards the evening and overnight hours. Saturday will be mainly cloudy with just a very slight chance of some showers through the daytime hours. As the evening approaches, though, it looks likely that thunderstorms will develop along the western escarpment of the Red River Valley and then progress eastwards across the valley overnight. At this point it looks like the storms will be non-severe, but we’ll keep an eye on them in case the threat increases as we get closer to the event.

The overnight low on Saturday night will be around 17 or 18°C.

Sunday will be another fairly cloudy day with a slight chance of some very light rain or drizzle as easterly winds keep the boundary layer socked in moisture while drier mid-level lift approaches. As the evening approaches, once again some showers or thunderstorms are possible. Expect a low in the low teens on Sunday night.

Next Week’s Weather?

At this point, next week looks much cooler and drier with more fall-like weather in place. Daytime highs through the first half of the week look to be in the 15–20°C range while overnight lows will drop towards the mid-single digits. Little precipitation is expected, and we’ll see more and more sun as the week progresses.


  1. PWAT stands for precipitable water, a measure of how much water is contained in a column of air.  ↩

Sweltering Heat Moves Into Manitoba

The coming days will be marked by a rare late-summer heat wave that will see hot and humid conditions moving into the Red River Valley, sending humidex values soaring towards the low 40’s. The hot weather will be relatively short-lived, though, as a cold front moving into the region on Friday will send temperatures back towards seasonal values alongside a returning chance for showers or thunderstorms.

Today and tomorrow will both be swelteringly hot days with daytime high temperatures in the low 30’s throughout Winnipeg & the Red River Valley. Humidity will increase dramatically this morning as temperatures begin to warm and the boundary layer deepens and taps into a significantly more humid air mass that’s moved in aloft overnight. By mid-to-late morning, dewpoint values will have climbed into the high teens or low 20’s across the Red River Valley. Combining the high dewpoints with the hot daytime high temperatures, humidex values in the upper 30’s to low 40’s are expected. Environment Canada has issued a heat warning for Winnipeg as well as many other areas across Southern Manitoba including the southwestern corner, Red River Valley, and southeastern Manitoba. Thursday will be slightly warmer and more humid than today is as both the temperature and dewpoint are expected to climb another degree or two higher.

RDPS Forecast Humidex valid the afternoon of Thursday September 3, 2015
The RDPS is forecasting a large swath of humidex values over 40°C (orange) in Manitoba on Thursday afternoon.

With such substantial humidity in place, overnight lows both tonight and tomorrow night will be quite warm, bottoming out near the 20°C mark. Additionally, expect just slightly breezy winds out of the south.

Friday will bring increasing cloud through the day as a cold front approaches from the west. Temperatures should manage to climb into the upper 20’s before the cloud cover cuts off our daytime heating. At this point, it looks quite likely that a large are of showers and thunderstorms will work their way across the Red River Valley through the afternoon. Severe thunderstorm potential looks minimal at this time, but we’ll keep an eye out and issue and outlook if it seems like it might pose more of a threat. Temperatures will cool down into the mid-teens on Friday night with clearing skies.