How can snow fall in Mexico when we have warm temperatures and no snow in Canada?
In winter, large undulations can develop in the jet stream, known as troughs and ridges. In a deep trough the jet stream dips far to the south before curving back towards the north. This can bring cold and snow to places like Texas and the mountainous regions of Mexico, despite their southern location. Often when there is a big dip in the jet stream, or trough, there will be a compensating area downstream where the jet stream bulges far to the north forming a ridge. Areas under this ridge, such as the eastern Great Lakes, often experience warm temperatures with no snow despite being farther north.
