"By early Friday morning the flow
aloft will change southwesterly as longwave trough digs into the
Rockies and Intermountain West. Lee cyclogenesis is forecast in
the Northern Plains Thursday night. The low pressure system will
likely lift toward the northeast into the southeastern Canadian
Prairies and northwest Ontario by Saturday morning. Deterministic
and ensemble models differ in the details, but seem to have good
agreement in the placement of the trough and eventual eastward
progression. Southwesterly return flow is possible ahead of the
system, which may support strong to severe thunderstorms Friday
afternoon and evening and perhaps again Saturday.
Temperatures will remain near to below normal for the long term
period with afternoon highs in the middle 60s to middle 70s and
overnight lows in the 40s and low 50s."