MODERATE risk of severe thunderstorm for Prairies


Manitoba

  • Area(s): Southern Manitoba

  • Timing: Monday afternoon, evening, and overnight

  • Threats: 2-4 cm hail, 90 km/h wind gusts

Scattered thunderstorms will develop over western sections in the afternoon ahead of a low pressure system approaching from the Saskatchewan. Isolated large hail and severe wind gusts will be possible with the largest thunderstorms. The severe threat will continue into the overnight hours, mainly for south central or southeastern sections of the province.


Saskatchewan

  • Area(s): Central and southeastern Saskatchewan

  • Timing: Monday afternoon and evening

  • Threats: 2-4 cm hail, 90 km/h wind gusts

Scattered thunderstorms will develop across most of central and southern Saskatchewan Monday afternoon as a low moves across the region. Isolated large hail and severe wind gusts will be possible with the largest thunderstorms. The bulk of the activity will move into Manitoba by late evening, though a few non-severe thunderstorms may linger into the night.




Saskatchewan into Manitoba...


A more significant clipper system will develop and move over the prairies Monday, with the low centre lying near Saskatoon by mid afternoon and at the Manitoba border near Yorkton by local midnight. The system will draw back northward more humid air, bringing dewpoints into the mid-teens with highs near 30 degrees Celsius. All together this is producing a swath of about 1000 J/kg MLCAPE over SE Saskatchewan and SW Manitoba wrapping about the low itself. While the low and surrounding troughing will provide good focus for ongoing surface-based thunderstorm initiation, a few limiting factors are in play for the day. Once again, Sunday's analysis is showing slightly reduced moisture over the warm sector source near Nebraska - actual dewpoints are reduced by a couple degrees from the models - and the ongoing haze and smoke may tamp down instability a bit further. Second, good shear and instability ingredients don't quite phase up; with the best dewpoints nearer to the international border, deep shear is very low coupled with poor upper level ventilation - only about 20 knots at 500 mb. Shear improves nearer to the low itself and into central Manitoba, but moisture is slowly decreasing and the capping inversion begins to increase, both hampering the potential for larger daytime convection. As such, widely scattered thunderstorms are still expected, but more of a pulse variety with poorer ability to organize and grow upscale. Latest CAMs are indicating this scenario as well. Analogues indicate there's still enough instability to produce severe hail with the possibility of severe wind gusts for the afternoon and evening for Saskatchewan and southwestern Manitoba. Later, as the low itself approaches Manitoba, the setup becomes elevated with good instability persisting over much of southern Manitoba through the night. Again, shear and winds in general are not favourable for good elevated organization either, but enough in tandem with the instability to continue the isolated wind/hail threat to the Ontario border by Tuesday morning.


To keep updated: http://umanitoba.ca/environment/envirogeog/weather/conv_otlk/