Area(s): Southern and central
Timing: Afternoon into the evening and overnight over southern areas; morning and afternoon over central and northern areas
Threats: 2-4 cm hail, 100-110 km/h wind gusts and local 50 mm rainfall over southern areas ; gusty winds, pea sized hail, locally heavy downpours over central and northern areas
Scattered thunderstorms will be ongoing through the morning hours across central Manitoba and will continue to lift northeastwards through the day associated with a low pressure system. Redevelopment is likely over southern Manitoba along a trough of low pressure late in the afternoon and evening. These thunderstorms will pose a severe risk with 2-4 cm hail, 100-110 km/h wind gusts and locally 50 mm rainfall as the primary threats. Additional waves of thunderstorms will be likely across southern and central Manitoba through the overnight hours into Saturday morning. These thunderstorms may also reach severe criteria. Over northern Manitoba, a few thunderstorms may also occur in the larger area of general rainfall but will not reach severe limits
The sounding above depicts a profile favorable for damaging winds. With DCAPE in the 1200J/kg range and the inverted-V profile, this screams downbursts with any thunderstorms that develop in southeastern Manitoba later today. The tornado threat will be very low due to the nature of elevated storms and unfavorable hodographs.
Above is a possible depiction of storms for southern Manitoba. You can see development around 7pm CDT.
Manitoba... While scattered nocturnal convection will be likely over western and central Manitoba this morning, the warm sector over southern Manitoba should see a fair amount of surface heating which will drive temperatures up into the low 30's. Strong low level flow (40-50 knots at H85; southerly surface winds of 40-50 km/h sustained) will advect moisture northwards over southern Manitoba with dew points climbing into the mid (to possibly even upper) teens by late afternoon. As such, MLCAPE values will be on the order of 1500-2000 J/kg. Given the large scale dynamics in place, the environment over southern Manitoba will also be strongly sheared with 30-40 knots of effective bulk wind difference with increasing values further northwards. A pre-frontal trough will be the focus for severe thunderstorm development during the late afternoon/early evening hours which will track northeastwards across the Red River Valley and into the Interlake. While warm mid-level temperatures will present some capping concerns, strong surface heating and modest moisture transport should permit storm development. Although slight timing and location differences exist, nearly all CAM solutions suggest severe thunderstorm development over the western RRV, justifying the inclusion of a severe threat area over south central Manitoba. A brief tornado threat may exist early in the life cycle of any storms if winds can locally back due to terrain or convergence along the trough, before quickly growing upscale into linear modes that would support mostly large hail, heavy rain and damaging wind threat (given rather large T-Td spreads). Given the high surface temperatures and modest moisture (with little ET component this early in the growing season), LCL heights will be rather high. Combined with unidirectional shear profiles, the overall tornado threat appears low.
For the latest updates go here: http://umanitoba.ca/environment/envirogeog/weather/conv_otlk/