811 FXUS63 KGRR 080709 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 309 AM EDT Tue Sep 8 2026 .KEY MESSAGES... - Showers/storms tonight/Wednesday - Low chance of showers Saturday - Stronger system possible Monday && .DISCUSSION... Issued at 308 AM EDT Tue Sep 8 2026 - Showers/storms tonight/Wednesday A cold front stretches from eastern North Dakota to central South Dakota. Radar and IR imagery shows abundant convection firing ahead of the front currently. As the front approaches Michigan tonight, we`re likely to see showers and thunderstorms move over the far northwest cwa late this afternoon and slowly move south across the cwa tonight and Wednesday. All of the ECMWF ensemble members show precipitation. Upper level flow is largely parallel to the front so we`re not going to see the front plow through quickly. A nocturnal LLJ will move over the cwa tonight advecting in moisture-rich air from the south; pwats climb to around 2 inches, which could result in moderate to locally heavy rainfall. However, MUCAPE is only a couple hundred j/kg. Thus thunderstorms may not be very robust and severe storms are not anticipated. RRFS model data has back off on thunderstorm strength during the past couple of model runs. That said, bulk shear values are in the 30-40kt range tonight and a bit higher Wednesday which may allow for locally stronger cells. Total qpf expected is a quarter inch or less south of I-96 and a quarter to two thirds north of I-96. Precipitation will diminish Wednesday afternoon as the front moves south and high pressure begins to move in from the northwest. - Low chance of showers Saturday Another front will approach Saturday, but the strongest dynamics with the system will be north in Canada, closer to the low over James Bay. Moisture return ahead of the front also isn`t stellar, so we only have 15-20 PoPs in the grids for this. - Stronger system possible Monday A better chance of rain will arrive next Monday when another front approaches. This time, though, there`s a much stronger shortwave accompanying it. Models show a tighter pressure gradient which could mean a breezy day ahead of the system. Most of the ECMWF ensemble members show precipitation with this system, and a few point toward heavy rain; there`s time to flesh out the details as it is almost a week away. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 104 AM EDT Tue Sep 8 2026 Abundant high clouds are noted on the latest IR loop. The TAF period will be dry, but clouds will gradually lower to around 10k ft by Tuesday evening in advance of the next cold front. && .MARINE... Issued at 308 AM EDT Tue Sep 8 2026 Southwest winds will increase today ahead of the next cold front that will move through Wednesday. Highest waves will be north of Holland and we issued a small craft advisory and beach hazards statement for this. Waves will increase to 3 to 6 feet and become hazardous to small craft this afternoon before decreasing Wednesday night. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from 2 PM EDT this afternoon through Wednesday evening for MIZ037-043-050-056. MARINE...Small Craft Advisory from 2 PM this afternoon to 8 PM EDT Wednesday for LMZ846>849. && $$ DISCUSSION...04 AVIATION...04 MARINE...04

NWS GRR Office Area Forecast Discussion