Today June 30, 2020
Threat level: MODERATE
Confidence: MODERATE (based on model agreements)
Expected hazards: DAMAGING WINDS // HAIL // FLASH FLOODING
Locations impacted: Southwestern Manitoba to Lake Manitoba: Brandon, Melita, Souris, Virden, Neepawa, Sandy Bay and surroundings. Later in the evening/overnight: Winnipeg, Carman, Portage La Prairie and surroundings.
Timing: 3pm CDT to 1am
Expected watch(s): Severe thunderstorm watches
Timing: Tuesday late afternoon into Tuesday night
Threats: 2-4 cm hail, localized rainfall of 50 to 100 mm, and risk of an isolated tornado transitioning to 2 cm hail and 100+ km/h wind gusts.
A cold front pushing into southern Manitoba will spread thunderstorms eastwards across southern portions of the province tonight. The highest likelihood of severe weather will be over southwestern Manitoba in the late afternoon/evening where heavy rain, damaging hail, and an isolated tornado will be possible near the Saskatchewan border. As the thunderstorms move eastwards overnight, they are expected to develop into a squall line and the primary threats will transition to damaging hail and wind.
Discussion: ENHANCED risk issued by the Canadian Prairie and Arctic Storm Prediction Centre (PASPC) and SLIGHT risk issued by the U.S. Storm Prediction Center (SPC) with mention of tornadoes for both. Thinking PASPC too reliant on HRRR, which shows more discrete cells across the forecast area. Thinking tornado threat is low (~2%) since multicells and bowing features will be primary storm modes. Low should sit near Minot, ND with a stationary front situated northeast of the low and extending into Manitoba. South and/or on/near the stationary front and just southeast of the low/east of the cold front is where storms are expected to develop. There are discrepancies between models, with the NAM 3km showing no storms developing and the HRRR showing intense storms developing near the ND/MB border near Minot and moving into Manitoba with a potential tornado threat/large hail. The likely scenario is storms developing north-northwest of Minot and move north-northeast across southwestern Manitoba, possibly with multiple rounds of storms impacting the area. Then, bowing segments are likely to move east-northeast across southern Manitoba, possibly reaching the City of Winnipeg in the overnight hours. Damaging winds, flash flooding and hail will be the primary risks across most of southern Manitoba.