textproduct: Grand Rapids

KEY MESSAGES

- Rain tapers off this afternoon/evening

- Mainly dry weather is expected from Monday through Friday

- Seasonable temperatures this week...feeling more like fall

DISCUSSION

Issued at 154 PM EDT Sun Sep 20 2026

- Rain tapers off this afternoon/evening

Precipitation is in the process of winding down this afternoon over Southern Lower Michigan. A zone of convergence in the 850-700mb layer is aiding the precipitation. Models show the axis of convergence moving southward steadily this afternoon and evening. Expecting the precipitation to come to an end by midnight. Low clouds will also trend southward and scour out along I-94 as we move into the late evening hours.

Rainfall of 2-3 inches has been common in the heavy rain area to the south and southwest of Grand Rapids. Some reports in excess of 3 inches are also noted on local observation sites.

- Mainly dry weather is expected from Monday through Friday

High pressure is situated over the Great Lakes region for essentially the entire work week. Ensemble members of both the GFS and the ECWMF indicate mainly dry weather leading to a high confidence forecast.

The only exception to this rule will be associated with an upper low seen spinning eastward across the state of Wyoming today. The upper low will work through our area Tuesday and Wednesday. At this point we have dry weather in areas that it traverses. The thinking is that too much dry air will be in place associated with the sprawling surface high. We will be monitoring forecast trends, but at this point at worst it would be a few isolated showers.

- Seasonable temperatures this week...feeling more like fall

850mb temperatures are expected to be in the single digits C this week, which will equate to conditions feeling much more like fall. The difference from this weekend to the upcoming work week is that it will be much less humid. Northeast winds via outflow from Canadian high pressure to the north will allow much drier air to filter in. Dew points at present are around 60F in Grand Rapids. We expect dew points to drop into the 30s and 40s F much of this week. That is a drop in humidity that will be noticeable. Highs this week will be in the 60s most days with lows in the 40s. For reference, normal high/low in Grand Rapids today 72 and 51. Bottom line...slightly cooler than normal temperatures combined with lower humidity will make for light jacket/sweatshirt weather.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 139 AM EDT Mon Sep 21 2026

A much less impactful forecast for aviation interests as compared to the last couple of days. VFR is expected to dominate, except for some isolated MVFR ceilings early this morning.

The lower clouds have just about all pushed south of our terminals as of early this morning. KGRR had some isolated 2500 ft ceilings, but that has since cleared out. The I-94 terminals still have a 6-9k ft agl ceiling, which will likely remain through most of today. Areas north will likely just have the high 20k ft deck, with maybe some isolated cumulus developing mid-late morning.

Winds will become a bit gusty with diurnal heating today from the NE. Gusts up to 25 knots will once again be possible, especially at the northern sites where the heating will be a little better with less layers of clouds. The diurnal cloud cover and gusty winds will diminish toward sunset tonight.

MARINE

Issued at 154 PM EDT Sun Sep 20 2026

A period of stronger winds will develop this afternoon and evening over Northern Lake Michigan especially, due to a tightening pressure gradient. A strong high to the north advancing southward from Canada will join forces with weak low pressure in the Ohio Valley to increase winds to 15-25 knots from the northeast. Waves spread out in all directions from the wind, so 3-6 footers will build into our forecast zones up near Big and Little Sable Point's (or areas north of Whitehall). We currently have a Small Craft Advisory in place for areas north of Whitehall to cover the threat of winds to 30 knots and waves of 3 to 6 feet. The SCA runs through 200am tonight and that end time still looks good.

A persistent area of high pressure will remain parked over Ontario, Quebec and the Great Lakes this week which will result in a easterly off shore wind. Waves should remain 2 feet or less this week once we get by this evening's higher winds.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.