Rain forecast: What to expect toward end of the month

It has been extremely dry across Michigan. We will have to see an overall rearrangement of the upper-air pattern to get into some frequent and meaningful rains. There is some hope on that change as we look a few weeks out.

Generally our state has had much less rainfall than normal since late July. We had a very wet pattern across Michigan in the first two weeks of July and then the rain stopped falling with regularity.

The upper-air wind flow is what dictates where our storm systems come from and if these storm systems are juiced up with moisture or moisture starved. To get what I call a “juiced up” storm system we will want to see a large bend in the jetstream over the western half of the U.S. and a southwesterly upper-air flow out of that big bend.

Look at the most reliable way to evaluate what the computer models forecast two weeks out. Below is the upper-air flow forecast at 15,000 feet up over the next two weeks. You’ll be able to easily see the bend in the jetstream west, which is what we call a trough of low pressure. Watch toward the end of the forecast as that change in the upper-air flow develops.

This is what we should be looking at around the end of October.

Here’s what that type of upper-air pattern would bring to Michigan. Storm systems will move off the Pacific Ocean and drop down into the southwest U.S. Those storm systems would then eject out of the Southwest and move northeast toward the Great Lakes region. The storm systems would develop a southerly wind ahead of them and pull moist air hanging over the Gulf of Mexico into the storm systems.

We would actually have some storm systems where the heaviest swath of rain could be one-half inch to one-inch of rain.

The question whether this will be a week or so change and only send one or two storms our way, or will it be a longer lasting pattern. The longer lasting patterns such as this tend to last a month to even as long as three months.

For now we just know there will probably be a few meaningful rain systems as we head into November. We are going to still need a lot of rain at that time.

As far as how long I think it will last? I do think it‘s a trend toward the more regular precipitation-makers as we head into winter. I don’t think the pattern will be as pronounced for all of November and December as it will be around Halloween.

If the Halloween southwest-to-northeast storm flow sticks around for winter, get ready for a big, messy winter. That type of upper-air flow would be a wetter-than-normal winter with some storms on the cold side resulting in snow storms. Some storms we would wind up on the warm side and get winter rains.

Remember to continue to water all of your trees, evergreens and shrubs that have been planted in the last year. They could die on you by spring if they go into winter all dried out.