Tuesday, September 20, 2016

Storm Track Just North of Area

The jet stream will shift well to the north for the remainder of the week and into the weekend. That is important for our neck of the woods for two reasons. First, since we will be located to the south of the jet -- which is just an area of very strong winds within the flow up in the atmosphere -- we will see southerly winds. It is winds from the south that usher in unseasonably warm temperatures during this time of year. In terms of the magnitude of the heat, we won't see record highs. But middle and even upper 80's have occurred already this week, and will likely occur again.
The humidity will also be abnormally high for this time of year through the weekend to accompany the hotter temperatures. The second impact that the jet stream's location will have on the Stateline is it places the region in a spot where rain and storms will likely occur multiple times. In these types of patterns, wherever the apex (top of the ridge, or jet stream arrows in the image above) is located usually represents the area where rounds of rain and storms will happen. That area will be Wisconsin, southern Minnesota, Iowa, and potentially northwest Illinois through the rest of the week.

These rounds of storms usually develop in the evening and use a nocturnal low-level jet stream, ample moisture, and warmth to maintain themselves through the nighttime hours. As meteorologists often say, "they round the ridge." That phrase refers to the areas of storms that develop. Once they do form, they usually congeal into a line and push southeast rapidly -- following the winds of the jet stream aloft. With the jet being just to our north this week, the locations with the best chance of seeing these lines of storms -- or MCS's -- will be Minnesota, northern Iowa, the eastern Dakotas, and Wisconsin. However, as is usually the case with these patterns, the MCS's will tend to have enough strength to push further south than forecast models suggest. That is why there is a chance that we could see some of these nighttime storms reach the region both Tuesday night and Wednesday night.

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