The Heat Is On; Thunderstorms Possible Saturday

While July has been relatively pleasant, temperatures have [somewhat surprisingly] been largely below seasonal for much of the month. That’s all about to change as significant heat builds across the region to round out the month.

A developing southerly wind of 20-30 km/h this morning will draw warmer air northwards out of the United States and help push daytime highs up to around the 30°C mark. Skies will remain mainly sunny and humidity in the mid-teens should keep things feeling relatively comfortable. Expect lows to fall to around the 19°C mark tonight with winds continuing out of the south and partly cloudy skies.

An upper ridge in place over Southern Manitoba today will bring warm temperatures to the region.

Saturday will see a cold front slowly sweeping across the province, bringing with it a severe thunderstorm risk. Before that, though, there will be a hot summer day on tap with highs once again near the 30°C mark under mixed skies. With the southerly winds slowly diminishing and dew points rising to around 19 or 20°C, it will end up feeling quite humid in the afternoon. The cold front will progress eastwards through the day, reaching the Red River Valley mid- to late-afternoon. As it pushes into the valley, it will bring with it the risk of severe thunderstorms.

Going over the MIST ingredients:

  • Moisture: Low-level moisture will be plentiful with surface dew points climbing towards the 20°C mark and with deep moisture extending towards 850 mb.
  • Instability: Slight to moderate instability will be in place. Mid-level lapse rates leave a bit to be desired with expected values only around 6-7°C/km, but this is somewhat offset by the substantial latent heat available through surface moisture. Depending on the exact orientation of this system, the heights may be rising as the front stalls, which would work against thunderstorm development.
  • Shear: Bulk shear values around 25-30 kt will be in place which is on the lower end of values. Low-level shear will likely be weak and mid-level shear largely unidirectional.
  • Trigger: The cold front will slowly slump southeastwards, gradually slowing into the evening hours.

The primary threats with any storms that develop will be large hail and damaging winds, although with dew points so high, torrential rain is likely as well. They would move southeastwards through the Red River Valley. The biggest question will be whether or not storms actually develop. The threat will exist generally around the Trans-Canada Highway corridor and south, but we’ll provide an update on Saturday with a new look at the day’s potential.

A cold front will be in place across Southern Manitoba on Saturday afternoon.

The thunderstorm threat will diminish before midnight and temperatures will then drop to a low near 17°C under clearing skies.

Sunday will be another hot day with a high near 31°C but more comfortable humidity as the dew point drops back towards the mid-teens. Skies will be partly cloudy and winds will be light out of the east. Winds will shift out of the south on Sunday night and increase to 15-25 km/h, keeping temperatures fairly warm; the overnight low will be just around 19 or 20°C.

Long Range

Temperatures will continue to be warm through the start of next week with partly cloudy skies and highs generally around the 30°C mark. Monday will likely be moderately humid again, but things will dry out on Tuesday as a cold front moves through. The rest of the week looks fairly quiet with near-seasonal temperatures and low humidity.

Cloudy, Cool Mid-Week Gives Way to Another Heat Wave

Temperatures will be well below-normal today as Winnipeg and the Red River Valley remain entrenched under a cool northeasterly flow behind yesterday’s low that moved through the region. Temperatures will rebound quickly, though, with well above-normal temperatures return for the end of the work week.

Today will see high temperatures some 10°C below typical seasonal as cool, cloudy weather hangs over the Red River Valley as northeasterly winds tap cooler air underneath a cold upper-level low crossing over the region. Skies will remain cloudy much of the day — there’s a slight chance we might see some sunny breaks late this afternoon — and there will be a chance for some light rain or drizzle, particularly in the morning hours. Temperatures will reach a high of only around 16°C1 with winds out of the northeast at 15-25 km/h.

Skies will begin to clear tonight as temperatures dip to a low near 11°C with light winds.

A cold low, shown here with closed height contours at the 700mb level, will move across southern Manitoba on Wednesday, keeping skies cloudy and temperatures cool.

Thursday will be a much nicer day as the remaining cloud cover clears out and temperatures climb to a high near 23°C under light winds. There may be some scattered clouds in the afternoon, but nothing that will spoil the sunshine. Expect clear skies on Thursday night as temperatures drop to a low near 13°C.

On Friday, the upper-level ridge that brought scorching hot weather to B.C. and the western Prairies last week begins building back into the region. Under sunny skies, temperatures in the Red River Valley will climb into the lower 30’s. Areas in the southwest corner of the province will be even hotter, with high temperatures climbing into the mid- to upper-thirties. Southerly winds at 20-30 km/h will be in place as a low pressure system slumps towards the region from the northwest. These winds will draw humid conditions northwards; by the end of Friday dew point values will climb into the low 20’s, making it feel positively muggy out there.

Very warm temperatures will build across the entirety of the Southern Prairies on Friday with highs in the 30’s.

Friday night will continue to be warm with lows dropping only to around 18°C.

Long Range

Northerly winds will move into the region on Saturday, flushing the humidity southwards and making for more comfortable conditions. Daytime highs will still remain in the upper 20’s or low 30’s throughout the weekend under mainly sunny skies. With the warm air still in place, overnight lows will still be quite warm, likely bottoming out in the upper teens.

The hot weather continues next week, but there are signs that there may be some unsettled weather to begin the week before things settle down again. No significant widespread rainfall is expected in the next week.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.


  1. Although if more clearing were to develop than expected, temperatures would quickly reach closer to 18 or 19°C. 

Stormy Tuesday Brings The Heat

The heat will be cranking up over the Prairies this week, and Winnipeg will see increasing warmth through the start of the week. A potentially stormy Tuesday will be a marked turning point as hot and muggy weather moves into the region. Heading into the second half of the week, conditions will be more settled but the heat sticks around for the foreseeable future.

A major pattern shift is underway that will bring a prolonged period of heat to much of western North America. Winnipeg will begin feeling the impact today as temperatures climb towards a high of 27°C under mixed skies. Winds will pick up out of the south-southeast to around 20 km/h in the afternoon as low pressure system begins approaching the province from Saskatchewan. The humidity will remain relatively comfortable today, though, with dew point temperatures expected to remain around 13 or 14°C.1

Winds will continue out of the south-southeast tonight with temperatures remaining warm overnight; the expected low is just 17°C as a warm front pushes across the Red River Valley.

The RDPS shows an organized line of thunderstorms developing on Tuesday afternoon.

Summer will arrive in all forms for Winnipeg on Tuesday. Now in what’s known as the warm sector, the humidity will rise quite quickly on Tuesday morning with dew points reaching around 18-19°C. Temperatures will climb towards a high of 29°C which will feel closer to the mid-30’s with the humidity factored in. For the afternoon, attention will turn towards the potential for severe thunderstorms as a cold front pushes southeastwards into the Red River Valley.

Going over the MIST ingredients:

  • Moisture: Plenty of moisture available with dew points in the upper teens being fed into any storms that develop. Moisture also seems to be relatively deep, so dramatic reductions due to mixing are unlikely.
  • Instability: MLCAPE values climb towards the 2000 J/kg mark with marginal capping. The low-level inversion will erode with the injection of 850 mb cooling while 700 mb temperatures remain below the 10°C threshold.
  • Shear: Surface – 6km bulk shear values peak around 30 kt which would be ample for storm organization.
  • Trigger: Two primary foci for convection: a pre-frontal trough that moves through midday, and then a cold front that pushes into the region mid- to late-afternoon.

These thunderstorms may be severe with the primary threats being large hail and localized flooding due to intense downpours. Strong wind gusts are possible with these storms as well. At this point, it seems like a tornado threat is unlikely, but we’ll keep an eye on things as they develop.

After the cold front slides through, winds will shift out of the northwest at around 15-25 km/h and the humidity will begin to ease as drier air moves into the region. Temperature will still remain warm, though, with overnight lows dropping only to around the 17°C mark once again.

Wednesday will be another hot day with temperatures climbing to around the 28°C mark with partly cloudy skies in the morning. The humidity will be much more comfortable than on Tuesday thanks to drier air that works in through the day and drops dew points back down to the low teens for the afternoon. Expect a low near 17 or 18°C on Wednesday night with a slight chance of another shower or thunderstorm as a weak disturbance slides through the region.

Long Range.

Looking further ahead, temperatures will cool towards seasonal to round out the work week as slightly cooler air moves in behind Wednesday night’s disturbance.

NAEFS 8-14 Day Temperature Anomaly Forecast — Valid July 10 – 17, 2017

The heat begins building back in through the weekend, and next week is looking quite warm and relatively humid as an upper ridge builds over the western Prairies, spreading above-normal temperatures across the region.

Winnipeg’s seasonal daytime high is currently 25°C while the seasonal overnight low is 13°C.


  1. The dew point only begins having a significant impact on how hot and/or muggy it feels once it begins climbing above 15°C or so.