668 FXUS63 KGRR 120617 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 217 AM EDT Wed Aug 12 2026 .KEY MESSAGES... - Showers and storms moving to the South; Patchy fog overnight - Chances for storms tomorrow - Next chance for Showers/storms over the weekend && .DISCUSSION... Issued at 303 PM EDT Tue Aug 11 2026 - Showers and storms moving to the South; Patchy fog overnight The quasistationary boundary continues to sag southward and will push any showers/storms in that direction. There has been some light rain along the I 94 corridor, with the anvil from the thunderstorms through southern Michigan bringing some rumbles of thunder and vicinity lighting to that region. However, the storms themselves continue their southward trek toward the southeast. Light winds, a moist surface layer and recent rainfall is a recipe for patchy fog overnight into Wednesday morning. Expect this fog to be dense at times and will linger through the morning commute. - Chances for storms tomorrow Though there is a signal for decent CAPE values from the SFC moisture and daytime temperatures into the 80s, the atmosphere is fairly stable, especially since the boundary remains to the south. Latest HREF does show the potential for a weak mid level trough and some shear through northern lower Michigan in the afternoon. That could take advantage of the 1K J/kg of CAPE Wednesday afternoon. For those reasons, SPC has a ribbon of marginal risk of severe storms through the central and northern half of Lower MI tomorrow afternoon and evening. - Next chance for Showers/storms over the weekend The large upper level low over northern Canada continues to send waves through Michigan through the week. However, we remain fairly stable through the latter half of the week with temperatures at, to below normal into the weekend. A large upper level low will move into the the Great Lakes region through the area mid to late weekend with chance for rain into Sunday. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 217 AM EDT Wed Aug 12 2026 The beat goes on in terms of aviation weather concerns today, they are the same as they have been the last few days, fog and storms. Variable conditions are in place to start the TAF period once again with LIFR to VFR weather occurring in close proximity. In a light wind / high moisture setup this is to be expected as radiational cooling allows for rapid fog formation and dissipation. We do expect a downward trend the remainder of the night however with fairly widespread IFR and LIFR forecast by 11Z. The fog and stratus should lift quickly once again today with VFR weather returning by 15Z-16Z. Storms are once again in the forecast today, but the signal is not as strong for certain thunderstorm development. We feel many of the TAF sites may stay storm free today with the bulk of the activity staying to the north, east and south of the TAF sites. A zone of storms are expected from portions of Central Lower Michigan into the Thumb today with another zone sweeping the MI/IN border once again. Therefore, we currently have dry TAFs going, but know given a scattered nature to the storms it is not out of the realm of possibilities to see some activity today. The better bet is for dry though. && .MARINE... Issued at 312 PM EDT Tue Aug 11 2026 Showers and storms will move to the south this afternoon and evening. A typical mid summer weather pattern will continue the next few days. Light winds will continue. Expect sunshine and some of our warmest water temperatures. Winds and waves will remain fairly light through tomorrow. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ceru AVIATION...Duke MARINE...Ceru

NWS GRR Office Area Forecast Discussion