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Small craft advisories, colder temps, showers most of this week

The Season of Fall Sets in
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Posted at 5:06 AM, Sep 28, 2020
and last updated 2020-09-28 05:06:54-04

WEST MICHIGAN — It may be hard to take after last week and the 70 and 80 degree temperatures and abundant sunshine we had...or perhaps folks are just ready for Fall, but this week will feature quite the stark contrast in weather. Sharply colder temperatures, off/on rain showers, and SMALL CRAFT ADVISORIES will be in effect on Lake Michigan for most of this week.

Normal high temperatures for this time of year have us in the upper 60s. Normal lows in the upper 40s. This week, we expect high temperatures mainly in the low/mid 50s with very little sunshine. A well developed, upper level trough in our jet stream will set up shop over the Great Lakes much of this week. You can see below on our forecast model the upper level pattern and the "trough" or dip in our jet stream over the area. That dip will allow the colder air from Canada to drop southward into Michigan, and frankly, pretty far south into the Gulf Coast states. The warmer region in the United States will be in the west, where a ridge or bubble in our jet stream will prevail.

With the arrival of the colder air, will come stronger winds that will likely mix down from the higher levels of the atmosphere. That means beginning Monday afternoon and continuing through at least Wednesday (probably longer), SMALL CRAFT ADVISORIES will be in effect on Lake Michigan with waves running at least three to five feet and higher. It's also worth noting that colder air coming over the relatively warmer waters of Lake Michigan may help induce a spinning motion that could generate waterspouts on Wednesday, Thursday, and Friday.

With the colder air and warmer lake, we're also likely to experience lake effect and lake enhanced rain showers. It's the same concept as lake effect snow, but falls as rain since it's too warm to support snow. Take a look at the upper level temperatures this week. These temperatures about 5,000 feet above the surface are a good measure or proxy for readings here at the surface. The image below is valid for today (Monday). Note the yellows and greens over Michigan and even warmer along the Gulf Coast.

The next image, valid for Friday morning shows how the colder air has penetrated the Great Lakes and all the way south into the Gulf Coast. Note the cooler color change. It's easy to see, even from a non meteorological perspective, what's coming this week. That said, this colder air intrusion will trigger a variety of other issues like higher winds on the lake, rain showers, lake effect, and just downright brisk, blustery conditions.

While I do believe our 80 degree temperatures for this season are likely over, I would expect to get back to at least 70 or better in October with sunshine. We typically see that each season. Get the complete West Michigan forecast at www.fox17online.com/weather.