WEST MICHIGAN-- The cool pattern we have been in recently is about to take a turn in a warmer direction starting early this workweek. We go from highs Sunday in the upper 60s to highs on Tuesday in the mid to upper 80s.
Lots of clouds will be around here on Sunday held readings 5-10 degrees below normal across West Michigan. (The average high for September 8 in Grand Rapids is 76 degrees.)
Increased sunshine on Monday will help temperatures to jump back into the middle 70s.
A warm front lifts northward late Monday night through Tuesday morning from south to north across the viewing area. The passage of this front early Tuesday morning could trigger a few isolated showers and thunderstorms, though a consensus of modeling seems to focus the best coverage of wet weather just off to our north. (See Monday's weather in detail)
This warm front will open the flood gates, figuratively speaking, to heat and humidity for Tuesday afternoon with temperatures projected to reach well into the 80s by day's end. With dew points working into the upper 60s to near 70 degrees, peak heat indices will likely arrive in the lower half of the 90s. Tuesday afternoon and evening should turn out rain-free for all of West Michigan.
The aforementioned warm front will try to slip southward later Wednesday as a cold front and may cause a few showers and thunderstorms to develop at that time. The close proximity of this front into Thursday will keep the chance for a few showers and thunderstorms in the forecast. The timing of any wet weather on Thursday will have to be ironed out in coming days. Many hours from Tuesday through Thursday will turn out to be rain-free with sunshine included, just very warm and humid with heat indices in the lower half of the 90s on each occasion.
A better chance for widespread showers and thunderstorms appears to come Friday morning as a low pressure system passing from western Minnesota into Ontario drags a cold front through West Michigan. With the current arrival of this cold front looking to be late morning / early afternoon Friday accompanied by increased rain prospects, we keep temperatures more conservative to wrap up the workweek and only top out in the upper 70s. Humidity will dramatically drop off Friday afternoon and evening putting an end to our 3 day stretch of high-level September heat and humidity.
Though it cools down a bit into the mid to upper 70s for Friday and Saturday of this coming week, there are signs that another surge of heat may be assembling for Sunday and particularly into the following workweek. If the latest model runs verify, this second round of heat could be more substantial than the one that is to arrive over the next few days.