High pressure will dominate the first week of fall

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WEST MICHIGAN — Fall officially arrives Monday night at 10:29 p.m., and it will arrive this week like a very gentle lamb, unlike years past. The only changes we’ll see are quiet, dry, uneventful conditions Monday through Sunday.

It’s not very often at all our forecast models show an extended period of quiet weather, especially in September. That said, hopefully the models verify and the pattern will remain locked in place.

So what exactly does a high pressure system mean to us as it builds in to the region? Unlike low pressure systems, these highs force the air to sink on a regional scale. It’s called subsidence. If you can force the air to sink, the end result is usually (but not always) sunshine and dry conditions. Recall that we need rising air in order to cool the parcel (of air) and get clouds and precipitation to form.

A ridge of high pressure (as it’s called) typically means the jet stream is pushing north of the region separating the cold air from warmer air. If it were dipping south of the Great Lakes, we’d refer to that as a trough, and we’d typically see cooler, unsettled, wet weather. That said, this ridge is expected to remain in place all week and keep us shielded from most clouds and precipitation. Temperatures are also expected to warm in to the mid to upper 70s through the week as well.

Take a look at several images from the Hydrometeorological Prediction Center (HPC) and their surface weather maps. These are for the true weather geeks who want to understand why this week will be quite remarkable. The one below is valid for Monday. Note the “H” or high pressure system will be close to the Great Lakes in each image and we will remain under its influence.

The next image below is the surface weather map for Tuesday.

The next image is the surface weather map for Wednesday.

The next image is the surface map for Thursday.

The next surface weather map is for Friday.

The next surface weather map is for Saturday.

And the final map is from Sunday. Note again the influence of high pressure in our region each/every day!

Of course, it’s always possible the ridge could break down or the models could be incorrect, but high pressure ridges such as this from the ground all the way through the upper levels of the atmosphere tend to set up shop and stick around for several days. I would recommend that you complete any unfinished work that needs to be done outside before the real cool air and wet weather settles in. Lets face it: It really doesn’t get much better than this. I think I’ll take my final Lake Michigan swim at Grand Haven this week! Enjoy!

The photo attached to this story was posted on my Facebook page by Jenna Swartz, taken at Pere Marquette Beach a few days ago. Make sure to click over to www.fox17online.com/weather for current temperatures, satellite, radar, and our 7-Day forecast.

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