The beginning of the month of August was relatively quiet in the North American weather market. There were a couple of tropical features, but they were marked by their languid movement (Debby) or hit small landmasses, away from the American shores (Ernesto). The severe season has been slowed as well. Debby was the only real tornado producer of the month to date.

This will be changing over the next several days, as is often the case as summer changes to fall. Not only should the Atlantic basin start getting moving — there are two curious looking features on the long range model guidance — but with the change in air mass coming with the change of season, there should be enough of a conflicting air mass to produce strong thunderstorms on a regular basis, at least for a few weeks.

This isn’t atypical. There is usually a secondary severe season in the autumn, though cold air is typically more forceful than warm air. As a result, the cold can more easily sweep warmer air away, while warm and cold do battle for longer in the spring. Even though the fall season is shorter, the storms can be quite powerful.

Such was the case in the Great Lakes early this week, where strong straight line winds brought damage to the Twin Cities in a couple of rounds, and then carried on through Wisconsin and eventually Michigan. Consider this the opening salvo of the Fall season.

Severe weather is much more challenging to predict at longer ranges than tropical weather, at least in terms of trends, so we don’t know exactly what to expect more than a few days out, but we do have the short range outlook, which is looking askance at the wave moving through the Dakotas today. Severe weather is possible today and tomorrow, and may carry through across the Great Lakes again as the weekend approaches. Eventually, it will work south again before winter finally seizes the scene.