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Indian Summer On Hold This Week

Posted at 6:19 PM, Sep 29, 2013

WEST MICHIGAN — Liking this unfall-like weather? We’ve had temperatures in the mid/upper 70s, even some 80 degree readings last week Friday…but how long can it continue?

First of all, this is NOT indian summer. In order to have a true indian summer, we must have a widespread, hard frost or freeze, then several days of above normal temperatures (typically in the 70s). Since we only had some patchy frost/freezing temperatures, nothing qualifies as indian summer yet.

This week will feature temperatures above normal with abundant sunshine through at least Wednesday. In fact, we expect to have another 80 degree day on Tuesday. Normal/average highs for this time of year have us in the upper 60s.

There are some changes coming up later in the week though. We have the chance for a few showers later on Thursday, with them becoming likely Friday, Friday night, and Saturday morning as a strong system moves in to the state. Preliminarily, our computer forecast models are indicating the possibility of one to two inches of rain in that time frame, windy conditions, and a sharp cool down after the cold front passes Saturday morning. Temperatures most of Saturday and Sunday may be stuck in the 50s until the trough lifts out of the Great Lakes.

So why the warmer weather? The biggest reason can be attributed to the upper level flow around 30,000 feet and our jet stream. It has typically been to the north in southern Canada. That’s where the storms have been travelling and that’s where the colder air is…locked up further north. When the jet stream gets a big dip or trough in it, it tends to generate colder temperatures and unsettled weather. We simply haven’t seen much of that lately. That said, this will not last forever.

As we get deeper in to the fall, the temperature gradient becomes greater between the northern latitudes and the equator. That tends to force the jet stream further south (over the Midwest) and generate colder temps and unsettled weather. So it indeed is only a matter of time!

The attached photo was snapped by Vickie Grant of Hastings at Sleeping Bear Dunes Park.

Got any last-minute things to do outside? How about one more boat ride before winterizing it? Perhaps some fishing before it gets too cold. Get the complete West Michigan forecast for the next seven days at www.fox17online.com/weather.