Many places across Lower Michigan will see some frost or freeze over this weekend into Monday. Areas that may escape the frost and or freeze will again be around Metro Detroit's heat island, the Lake Shores and where patchy areas of clouds hold on. The brisk fall winds, which are also a hindrance to frost/freezes should gradually abate as we get into the new work week. The weather early to mid week looks like it will improve nicely with time with gradually warmer temperatures along with considerable sunshine and pretty much dry. With a little luck, we may even make it through next weekend (I won't let it rain on my birthday - lol, famous last words). The improvement will largely depend on how fast the upper closed low pressure over the east moves out. Past experience and recent trends suggest it will take its good ole time but still, the weather should improve (warmer) as the week evolves. Above normal temperatures (normal highs in SE Mich for this week are generally lower to mid 60s) will creep back into the picture and fulfill our Indian Summer (or Indian Summer-like) weather criteria by mid week into the weekend.
With time, an impressively strong summer-like ridge of high pressure aloft (heights flirting with 596-600 on European for wx buffs) will translate down to the surface and dominant the region. Both models agree with bringing this mammoth upper level and surface ridge over the region late in the week. The European is slower to give our eastern upper low the boot and that looks like the more likely scenario. We'll see how this forecast unfolds this week and hopefully, the models have a good handle on the general overall pattern evolvement and nothing goofs it up! However, if continues as progged, temperatures pushing up into 80s are not out of the question at its warmest. Records next weekend into early the following week, however, are quite warm (and generally the peak for October) running from the mid 80s to lower 90s. Ironically, just a few years ago in 2007 we topped out at 90 on the 8th at Detroit, 91 /7th/ at Saginaw and 88 /7-8th/ at Flint. The highest records for October are 91 /6th/ and 92 /7th/, back in 1963 at Detroit.
Ideal Indian Summer weather occurs when there has been a killing frost or freeze on vegetation and then a nice, long term warm-up with several days of above normal temperatures, generally gradually hazier weather with mainly dry conditions. Of course every year this does not happen over Lower Michigan at the same time. Generally, the frosts/freezes gradually make their way south and southeast with time. Areas near the warmer Great Lakes may take a little longer with the lake's moderating affect. In Southeast Michigan, I observed over the decades I worked with the NWS there were usually waves of frosts/freezes that overspread the region from northwest to southeast. The metro Detroit area extending east out around Lake St.Clair and along with the downriver communities south to the Lake Erie shoreline were usually the last to give way to the killing cold. When the balmy warmer winds do return, some areas still haven't had that killing frost/freeze, therefore I think the term "Indian Summer-like" weather suffices here.
Broadly speaking, most areas in Southeast Lower Michigan have seen some type of killing frost/freeze by the third or fourth week of October but not always. I can recall one or two years where some of the hardier vegetation was still creeping along at Thanksgiving and even early December but that was rare. I recall my roses (protected and along the house) still holding on to a bud or two at that time. Alas, only the plants that are the hardiest of lot continue a little longer as the frost/freeze sensitive plants are almost always wiped out by early-mid November.
Try to get out and enjoy one of the most beautiful times in Michigan!