Massive supercells erupt in SK/MT, similar expected tomorrow in MB


Above is a satellite depiction of massive supercells erupting in Saskatchewan and Montana along the warm front. This front is set to eject into Manitoba tomorrow and a similar scenario could unfold. Multiple isolated supercells are expected to develop in Manitoba tomorrow.



Wednesday


Threat level: HIGH

Confidence: HIGH (based on model agreements)

Expected hazards: VERY LARGE HAIL (up to baseballs) // DAMAGING WINDS // TORNADOES // FLASH FLOODING

Locations impacted: Russell, Shoal Lake, Brandon, Souris, Melita, Killarney, Virden, MacGregor, Neepawa, Pipestone, Peguis, Asher, Dauphin, Sandy Bay and surrounding towns (in Manitoba)

Timing: 4:00 pm CDT to 8:00 pm CDT

Discussion: steep lapse-rates, little to no convective inhibition ahead of the front, very high mixed-layer instability and ample moisture will make for a volatile setup for severe weather in southern Manitoba on Wednesday. What makes this setup that more "dangerous" is that one or a few lone supercell(s) is/are expected to form (somewhere in Westman) and track south-southeast into southwestern Manitoba. These lone supercells will have all hazards possible (including some tornadoes or possibly one stronger tornado), possibly for several hours, as it taps into unlimited instability/moisture with little competition. Storm mode is expected to be high-precipitation (HP). With this type of storm mode, heavy rain leading to flash flooding and very large hail can be expected. The tornado threat could be dampened by the evaporative cooling common in HP cells, which tend to easily undercut the updraft. Early initiation or overnight storms could also limit strength of storms. However, local terrain enhancements and possible outflow boundaries could compensate and enhance low-level shear. While we think the NAM 12km is overdoing instability, we still think that 2000-3000J/kg of MLCAPE could be realized in southern Manitoba on this day and for this reason have issued a HIGH risk of severe weather for this day.