A low pressure system tracking eastwards through Saskatchewan will bring a potent severe thunderstorm threat to Southern Manitoba today. The development of severe thunderstorms capable of producing damaging hail and winds, torrential downpours, and tornadoes is expected this afternoon over portions of southwestern Manitoba. These thunderstorms will then track eastwards across the Red River Valley & the southeastern corner of the province through the evening hours.
Hot and humid weather will return to Winnipeg today as temperatures soar to the 30°C mark while dewpoint temperatures climb towards the 20°C mark in the Red River Valley courtesy a gusty southeasterly wind of 30-40 km/h that will develop midday. This hot and humid weather will serve as the pressure cooker for severe thunderstorm development as a low pressure system tracks into the province this afternoon.
Through the morning hours, a few isolated thunderstorms are possible across the southwestern and south-central portions of the province, but they aren’t expected to be particularly notable. By early to mid-afternoon, the “main event” will start with thunderstorms developing along a north-south line west of the Red River Valley. Through the late afternoon into the evening, these thunderstorms will move eastwards across the Red River Valley and southeastern Manitoba.
These thunderstorms will be capable of producing large and damaging hail, dangerous straight-line winds exceeding 100 km/h, and torrential downpours capable of flash flooding. In the early hours of the system, over portions of southwestern Manitoba and possibly extending into the western Red River Valley, these thunderstorms will also be capable of producing a tornado.
Going over the MIST ingredients for convection:
- Moisture: Dewpoints climbing into the 20-23°C range will combine with moderate vertical extent as an organized moisture feed advects into the province from the Dakotas.
- Instability: Significant moisture coupled with moderate mid-level lapse rates to produce MLCAPE values 2000-3000 J/kg. MUCAPE values of 1500-2000 J/kg will continue overnight into northwestern Ontario.
- Shear: Significant speed and directional shear will be in place over the province with textbook-quality looping hodographs present under 50-60 kt of 0-6km bulk shear will practically guarantee supercell development upon storm initiation and will be completely supportive of upscale growth into the overnight period.
- Trigger: A frontal wave passing by the province and associated low pressure system and trough will provide ample lift and convergence to trigger thunderstorm development.
As storms develop, they will very quickly begin rotating and mature into supercell thunderstorms. These storms will very quickly develop hail and severe wind threats. Low lifting condensation levels coupled with the strongly veering hodographs and notable low-level CAPE also suggests a tornado threat for the first few hours of the storm life-cycle. This will most likely be constrained in an area from Brandon to Winnipeg along the Trans-Canada Highway and then south to the American border.
The severe thunderstorm threat will continue eastwards with the line through the evening into Ontario.
The thunderstorms will track eastwards through the evening hours, with Winnipeg most likely seeing the activity between 8PM and 1AM.
Winds will diminish tonight behind the thunderstorm activity as temperature dip to around 17°C.
Update: EC Event Summary
Environment Canada has issued a summary of the severe weather that occurred across #MBstorm yesterday. The highlights are two confirmed tornadoes, loonie to quarter sized hail, wind gusts up to 111 km/h, and 4″ of rain!
Weather summary for Manitoba issued by Environment Canada at 5:04 a.m. CDT Thursday 4 August 2016. Discussion. An intense low pressure system tracking across the Prairies brought widespread severe weather to much of southern Manitoba on Wednesday. Two tornadoes have been confirmed, and numerous reports of heavy rain, damaging winds, and large hail were also received. The following reports have been received by ECCC meteorologists (event times are approximate): A funnel cloud was reported 8 km north of Hartney at 5:00 pm CDT. A brief tornado was reported near Margaret at 5:10 pm CDT. No damage was reported with this tornado. A larger, longer lived tornado was reported 10 km west of Baldur at 5:20 pm CDT. It tracked northwards towards Stockton where a large shed was destroyed shortly after 5:30 pm CDT. ECCC meteorologists continue to investigate these and other unconfirmed tornadoes. Hail reports: Loonie sized hail at Brandon at 6:05 pm CDT. Quarter sized hail at Shoal Lake at 9:20 pm CDT. Loonie sized hail at Wasagaming at 10:10 pm CDT. Peak wind gust reports: 111 km/h at Morden at 7:26 pm CDT. 93 km/h at Portage la Prairie at 7:10 pm CDT. 92 km/h at St. Adolphe at 9:05 pm CDT. 85 km/h at Gretna at 7:46 pm CDT. 74 km/h at Winnipeg Airport at 9:45 pm CDT. Rainfall totals in millimetres: Erickson 104 Neepawa 75 Glenboro 66 St. Adolphe 64 Holland 56 Ethelbert 53 Fisherton 53 Morden 53 Killarney 50 Souris 49 Cypress River 45 Elm Creek 43 Snowflake 43 Winnipeg The Forks 2.7 Winnipeg Airport 1.4 Environment and Climate Change Canada meteorologists are actively seeking pictures or videos from Wednesday's severe weather events and further damage they may have caused. Should you have any information regarding these events or to report severe weather at any time, please call 1-800-239-0484, email storm@ec.gc.ca, or tweet #MBStorm. Please note that this summary may contain preliminary or unofficial information and does not constitute a complete or final report. End/PASPC
The Rest of the Week
Thursday will be a cooler day with a high near just 21°C with gusty northwesterly winds at 30-40 km/h. There will be a slight chance of some showers as the wrap-around from this low moves across the province. The humidity will be flushed out of the province making for more comfortable conditions. Temperatures will dip to 13°C Thursday night with clearing skies and diminishing winds.
Friday will be a pleasant day with winds out of the northwest at 20-30 km/h, highs in the mid-20’s and mainly sunny skies.
Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.
