Severe weather outbreak in Saskatchewan/Manitoba this weekend. Several tornadoes possible.

Updated: Jul 14, 2019


A ridge of High pressure, depicted by the blue "H" above, will maintain its hold on the North American continent. This will dictate the weather pattern for the Prairie Provinces. This ridge will allow warm moist air to maintain over the Prairies for a few days. Below we discuss severe weather potential for Saturday to Monday.



Saturday


Threat level: LOW

Confidence: HIGH (based on model trends)

Threat area: central Saskatchewan

Main hazards: LARGE HAIL // DAMAGING WINDS

Possible cities impacted: Saskatoon, Regina, Yorkton, Outlook

Timing: afternoon and evening hours

Discussion: isolated storms should develop near Saskatoon along the cold front (depicted in blue above). Aided by veering from Low pressure in southwestern Saskatchewan, storms could become organized and supercellular. Storms should remain isolated in nature and move in an east-southeast fashion. Below is the PASPC day 2 outlook:

Saskatchewan

  • Area(s): Southern and Central

  • Timing: Saturday afternoon, evening, and overnight

  • Threats: Hail 3-6 cm, wind gusts to 120 km/h, and heavy rain

Thunderstorms will develop ahead of a low pressure system near the Alberta/Saskatchewan border as well as a cold front further north. Instability is highest towards the southeast, and thunderstorms are expected to be strongest in this area. In addition, while individual cells are possible in the afternoon and evening, organized activity may also push northeastwards out of Montana or Alberta throughout the evening and overnight periods.

High humidex values for Saturday in Saskatchewan/Manitoba

Manitoba

  • Area(s): Southern and Central

  • Timing: Saturday late afternoon, evening, and overnight

  • Threats: Hail 3-6 cm, wind gusts to 120 km/h, and heavy rain

Scattered thunderstorm activity will develop along a cold front in northern Manitoba in the afternoon hours. Further south, isolated activity is also possible late afternoon over the Parklands, with an increasing chance of more thunderstorms into the evening hours as thunderstorms develop and organize in Saskatchewan. Convection will continue through the night, reaching eastern Manitoba and the Red River Valley by late overnight.



Sunday


Threat level: MODERATE

Confidence: MODERATE (based on model trends)

Threat area: Westman (western Manitoba) // eastern Saskatchewan

Main hazards: LARGE HAIL // DAMAGING WINDS // POSSIBLE TORNADO

Possible cities impacted: Swan River, Dauphin, Russell, Neepawa (in Manitoba) // Yorkton, Preeceville, Hudson Bay (in Saskatchewan)

Timing: late-afternoon (for Saskatchewan) an overnight (for Manitoba)

Discussion: a fairly complex weather scenario will unfold on Sunday. A weak Low pressure will set up shop somewhere in Westman (in western Manitoba) on Sunday afternoon. This will have a stationary front extending into central Manitoba and all the way to Hudson Bay. While the fronts may change, the High pressure (depicted above by an "H") will provide "Arctic outflow" or cold air towards Manitoba. While not depicted here, this will act as a cold front. Counterclockwise motion from the Westman Low will drag warm-moist air into central Manitoba and parts of Saskatchewan. This counterclockwise motion, the Arctic front AND terrain influences from the Manitoba escarpment will initiation vigorous thunderstorms somewhere in SK in the afternoon on Sunday. These should track southeast into Westman in the evening hours and intensify. The latest NAM 3km below depicts what the radar might look like, showing a lone supercell on the SK/MB border at 7pm CDT. Some additional supercells may develop near Dauphin and Sandy Bay as depicted below, which will have no problem becoming severe.

Tornado Potential


While it is a bit early to assess accurately the tornado potential, we think that this setup could provide the necessary ingredients for a few tornadoes in the Westman region, with the possibility of one being on the stronger side (EF1-EF2) range. While keeping in mind that science is simply not there yet, we can estimate what the atmosphere MIGHT look like in the vicinity of Dauphin-Sandy Bay-Neepawa-Russell on Sunday by looking at a "sounding" below. A sounding is like launching a weather balloon and recording temperature, dew points and winds as it goes up in the air.

This sounding provides vital clues as to what the pre-storm environment might look like. If a storm enters this sampled environment, tornadoes may occur. An elongated hodograph with veering of the winds and 90 degree 1km to 6km wind barbs indicate an environment suited for tornadoes. Adding the tilt of the storm, the 0-1km SRH and instability in the 2000-3000J/kg range, a stronger tornado is not out of the question on this day. The 6-9pm CDT time frame will need to be monitored closely on Sunday. If a storm interacts with the pseudo-warm front, we could have a serious storm on our hands.



Sunday Update


Overnight storms will cause a delay in storm development for Manitoba. We are now looking at the overnight time frame for more severe storms. Because of this, we are expecting less of a tornado threat and more of a damaging wind/hail threat. Storms will develop in the same area outlined above, but may be more multi-cell in nature before merging into a line then moving southeast overnight.



Saskatchewan

  • Area(s): Southern

  • Timing: Sunday afternoon and evening

  • Threats: 3-5 cm hail, wind gusts to 110 km/h, risk of a tornado

Severe thunderstorms look poised to hit southern Saskatchewan again on Sunday. Thunderstorms will form in the afternoon and persist until the late evening hours. Large hail and damaging winds are likely, but a tornado or two cannot be ruled out, especially in the late afternoon and the evening before dark.


Manitoba

  • Area(s): Southern

  • Timing: Sunday afternoon and evening

  • Threats: 3-5 cm hail, wind gusts to 110 km/h, risk of a tornado

Severe thunderstorms are expected in southern Manitoba on Sunday. Thunderstorms will form in the afternoon and persist until the late evening hours. Large hail and damaging winds are likely, but a tornado or two cannot be ruled out, especially in the late afternoon and the evening before dark.



Monday


Threat level: HIGH

Confidence: LOW (based on model trends)

Threat area: SE, Central Manitoba // eastern North Dakota

Main hazards: LARGE HAIL // DAMAGING WINDS // SEVERAL TORNADOES POSSIBLE

Possible cities impacted: Winnipeg, Gimli, Steinbach, Grand Forks, Morris, Pinawa, Kenora, ON

Timing: too early to say

Discussion: a possible high-impact severe weather event may ultimately unfold on Monday. The Low will move east, dragging a cold front into central Manitoba and a warm front into the Whiteshell region. While this setup will be quite dependent on the overnight storms from Sunday, some significant severe weather is possible for southeastern Manitoba and eastern North Dakota on Monday. The confidence is low at this time, pending further investigation. Storms on the warm front will be the ones to watch for a possible tornado outbreak. A secondary area of concern would be where the cold front and warm front intersects, nearest to the Low pressure in southeastern Manitoba. Please stay tuned as we refine our forecast in the coming days.