The west end has had some huge rainstorms during the month of July. One of them occurred in Ironwood on July 16-17, 1942. During a 24-hour period, the town was inundated with 6.70 inches of rain.
The pattern that brought the soaker was not unusual for summer. A big, hot ridge built to the south over the Mid-Mississippi River Valley (Image 1 above). To the north, Upper Michigan was right on the far southern portion of the main band of westerlies. In this position, disturbances topping the ridge will spark showers and thunderstorms. The outer periphery of the ridge is sometimes called the ??Ring of Fire?? because of the complexes of thunderstorms (Fire-Lightning) produced by the disturbances. In the 1942 situation, low pressure in the Plains funneled a very warm and humid air mass into the U.P. and helped to produce the very heavy rain (Image 2).
The situation developing over the next couple of days is roughly similar to the situation 71 years ago. By tomorrow evening, the westerlies will finally be sinking back south into the Upper Great Lakes (Image 3) as the big ridge that??s been dominating gets beaten down. As this occurs, the main front will set up close by as low pressure develops in the Plains (Image 4). The low will help bring up even more moisture which will produce pockets of heavy rain. It all depends upon where the slow-moving front intersects this rich moisture because that is where the heavy downpours will occur.The front will get a shove south on Friday. This will dry things out and allow much cooler air to pour in on northwesterly winds.