188 FXUS63 KGRR 220804 AFDGRRArea Forecast Discussion National Weather Service Grand Rapids MI 404 AM EDT Mon Sep 22 2025
.KEY MESSAGES...
- Chances for showers and storms the next 3 days
- Drying out towards the end of the week and into the weekend
- Temperatures near to above normal
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.DISCUSSION... Issued at 403 AM EDT Mon Sep 22 2025
- Chances for showers and storms the next 3 days
All of southwest Lower Michigan is in a general thunder outlook from the SPC for today, Tuesday and Wednesday. This is due to the fact that we do not change the airmass (surface dew points in the 60s) through Wednesday. Aloft, we are located in the southern portion of an upper trough both today and Tuesday and move beneath a developing upper low on Wednesday. What this means is unsettled weather will continue with a diurnal boost to showers and storms each day. The instability lessens a bit each day as the surface boundary associated with the upper trough slides south into and through the area. We cannot rule out a few storms each day however. Not expecting severe weather with any of the activity given weak flow (generally 25 knots or less of wind from the surface through the mid levels).
- Drying out towards the end of the week and into the weekend
We look to dry out as we get out into Friday and into the weekend as the flow transitions to zonal and then ridging into Sunday. Given drier air in the low levels we have a mainly dry forecast from Friday through Sunday.
- Temperatures near to above normal
850mb temperatures are about where we would expect for this time of year between +10C to +15C. This should equate to high temperatures in the 70s most days. By next weekend climo values are trending into the upper 60s as we close in on October. Pleasant weather for sure with mainly dry conditions and warmer than normal temperatures.
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.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 220 AM EDT Mon Sep 22 2025
Largely expecting VFR weather the next 24 hours. The exceptions are some MVFR ceilings/visibilities that may develop early this morning and some scattered showers/storms this afternoon that could bring locally lower aviation conditions as well.
First off is the threat for some light fog and stratocumulus development early this morning that may persist into the daylight hours of Monday morning. A weak pressure gradient this morning when combined with a moist airmass in the low levels will lead to some MVFR ceilings and visibilities. We expect these conditions to lift by 15z-16z at the latest.
This afternoon we are expecting some scattered showers and storms to develop. The highest likelihood of seeing this activity will be towards the I-94 TAF sites. At this point just have VCSH/VCTS wording in the TAFs. If the confidence in coverage increases we will include SHRA/TSRA in the prevailing groups.
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.MARINE... Issued at 403 AM EDT Mon Sep 22 2025
Winds and waves are expected to remain below advisory levels through much of if not all of the work week. A lax pressure gradient is in place this morning across the region and that will remain the case into Tuesday. There will be an increase in north and northeast flow Tuesday evening into Wednesday as the gradient tightens for a time between low pressure to our south and a high off to the north. We are not expecting conditions to become elevated enough though to warrant a Small Craft Advisory or a Beach Hazards Statement. Waves should be 2 feet or less through the week. For what September can bring to the waters of the Great Lakes this will be a tame week on the big lake.
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.GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None.
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DISCUSSION...Duke AVIATION...Duke MARINE...Duke
NWS GRR Office Area Forecast Discussion