Our second Indian Summer arrives this week

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WEST MICHIGAN — Consider it a bonus this year in West Michigan. Whether it’s politically correct or not, some of us old fashioned folks know the term Indian Summer and have experienced many of them in our years. That said, a second Indian Summer will arrive this week as our headlines indicates.

So we’re all on the same page, Indian Summer refers to a period of above normal temperatures with dry conditions and sunshine. What differentiates Indian Summer from any other period of weather like this is when it occurs. In order to be called or classified as such, it must occur AFTER the area experiences our first widespread hard frost/freeze. Yes there were several days here and there where some locations saw patchy frost, but it wasn’t until October 17 and 18 when many locations recorded morning lows in the 20s and below freezing temperatures again on October 19. Despite the fact the mornings were cold and frosty, Grand Rapids and many other locations saw our daytime highs rebound substantially in to the low 70s October 19, 20, and 21. That technically qualifies as our Indian Summer.

This week we’re forecasting high temperatures in the upper 60s/low 70s. Despite the low sun angle this time of year, something called warm air advection will move the mercury 15 to 20 degrees above normal. Advection is simply the transporting of something from one location to another. In this case, temperatures to our south/west in the Midwest and Central Plains are in the low/mid 70s. That warmer air will be transported in to Michigan with a brisk southwest wind on Monday. A warm front will form to our west and lift in to the northern Great Lakes by Tuesday and Wednesday. That will keep us in what meteorologists refer to as the warm sector with a defined southwest flow pumping in the warmer air.

The image attached to this story is from one of our computer forecast models. It’s valid for Tuesday morning. The colors indicate the air masses about 5,000 feet above the surface or around 850 millibars for you weather geeks. The warmer tones indicate warmer air masses and the colder tones indicate colder ones. Notice how the colors over Michigan are primarily yellow. That color corresponds to temperatures 5,000 feet above the surface at 12 degrees Celsius or about 54 degrees Fahrenheit. Those temperatures aloft will likely translate to the upper 60s/low 70s here at the surface!

So enjoy the briefly milder temperatures this week. It’s not out of the question we experience 70s again this season, but it’s becoming increasingly unlikely this late in the season. Our next rain chance arrives Thursday night in to Friday with highs only in the 50s by the end of the week. Get the complete West Michigan forecast at www.fox17online.com/weather.

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