807 FXUS63 KGRR 050817 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 417 AM EDT Sun Jul 5 2026 .KEY MESSAGES... - Chances for thunderstorms once again today - Dry weather Monday Night through Wednesday - Showers and storms possible Wednesday night and Thursday && .DISCUSSION... Issued at 415 AM EDT Sun Jul 5 2026 - Chances for thunderstorms once again today Multiple meso vorticity maxima have rotated eastward across Northern Indiana tonight. This has produced a zone of convergence over far Southern Lower Michigan, including the I-94 corridor. The FV3 seems to have the best handle on this and we expect to see an uptick in coverage and intensity over the next few hours or through 12z-13z. Deep layer shear is very weak and instability is not strong (500-1000 j/kg). So, while we expect a few storms early this morning we are not anticipating anything close to severe. A surface low will be just south of the region today over IN/OH. There may be just enough lift and instability to see another small round of storms this afternoon and evening from Holland to St. Johns southward. The HREF shows this well. Cannot rule out some locally heavy rain today near I-94 with the HREF indicating some localized swaths of 2-4 inches possible. Most areas will not see this much, but with convergence and high PWATs these values are reasonable in an isolated max forecast. Chances for showers will persist tonight and into Monday across the far southern CWA as the low to our south does not move much. - Dry weather Monday Night through Wednesday We look to be dry Monday night through Wednesday with high confidence in ridging persisting over the Great Lakes. BUFKIT overviews show very little moisture in the profile. Highs in the 80s and lows in the 60s will feel more comfortable, especially with lower dew point air settling in on northeast winds. - Showers and storms possible Wednesday night and Thursday Our next chance for rain will come Wednesday night and Thursday as a cold front presses in from the northwest. Surface dew points will rebound to 65F to 70F which will push MUCAPE values to in excess of 1000 j/kg. Thunderstorms will certainly be possible once again during this time frame. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 210 AM EDT Sun Jul 5 2026 Quite a bit of aviation weather to talk about this morning. First order of business is the chance for showers and thunderstorms at the I-94 TAF sites through roughly 12z or so. A compact mid level disturbance rotating east across Northern Indiana may provide lift along I-94, enough that showers and storms will be generated. At this point have hit the AZO TAF site the hardest, but we may need to expand the threat to BTL and JXN as well. Next item is the threat and expanding area of stratus this morning. The stratus and light fog looks to expand before daybreak to affect most of the TAF sites by 12z. The exception may be MKG. The stratus and fog may take most of if not all of the morning to lift. VFR weather is then expected in the mid to late afternoon. Another round of showers and thunderstorms will be possible after about 20z. && .MARINE... Issued at 415 AM EDT Sun Jul 5 2026 Winds for the most part will be light over the next 4 days. There will be some stronger off shore winds tonight in the 10-20 knot range, but they will be northeast/off shore. Therefore, waves over the next 4 days in West Michigan will largely be 2 feet or less in the nearshore waters. The one item to watch in the next few days is that Monday could feature our advancing high scenario where we see higher than forecast winds and waves. It would be centered on Monday afternoon and early evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion