346 FXUS63 KGRR 030800 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 400 AM EDT Thu Sep 3 2026 .KEY MESSAGES... - SPC Slight Risk for severe weather over much of the area today - Thunderstorm chances may linger into Friday - Dry weather expected over the weekend && .DISCUSSION... Issued at 400 AM EDT Thu Sep 3 2026 - SPC Slight Risk for severe weather over much of the area today The pattern continues to support the threat of thunderstorms over the next 24 hours, including both today and tonight. At the surface we have essentially a stationary boundary stretching from east/west near the I-96 corridor. Dew points to the north are in the 60s and are in the 70s to the south. MUCAPE values are stratified correspondingly with 2,000 j/kg in place to the south and 500-1,000 to the north. The upper flow pattern will likely bring in convectively induced vorticity maxima from the west today (the IA/MN convection). Tonight models suggest a NW to SE moving shortwave that may bring additional storms to the area. The best LLJ orientation and magnitude occur early this morning through sunrise and again tonight coming up. Confidence in the evolution remains on the lower side today/tonight, but we do feel we will likely see additional storms this morning, additional chances this afternoon, followed by more storms tonight. Wind appears to be the main threat per machine learning data like NadoCast which is supported by the SPC outlooks. Early afternoon soundings via the HRRR in Ottawa County are indicating 1,100 j/kg of DCAPE which shows the potential for damaging winds. PWAT values continue to be high both today and tonight with 2.0 values both forecast periods. Storms have the potential to be moving quickly, but rainfall rates will likely be high given deep summer values of PWAT. If storms can train over certain areas or if motion is slower than anticipated hydro concerns will increase (localized short term flooding). - Thunderstorm chances may linger into Friday Models indicate the potential for some storms lingering into Friday morning in a northwest flow aloft just downstream of the plains upper ridge. SPC has a marginal threat for severe weather in our far southwest which makes sense given the moisture will be pooled in this area as the front likely sags to the southwest. - Dry weather expected over the weekend The patterns looks to try and dry out this weekend as high pressure builds in from the north and northeast. BUFKIT moisture overviews this weekend are starkly drier than what we have seen all this week. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 156 AM EDT Thu Sep 3 2026 Skies are partly cloudy as we approach 06z across Southwest Lower Michigan with VFR bases. The clouds are generally in the 5,000 to 10,000 foot layer and are associated with a weak front in the area. The front is producing showers and a few thunderstorms mainly near I-96. There is a chance these showers and storm expand through the remainder of the night and we will be watching that closely. Otherwise some patchy light fog has formed across the area. As we progress into the daytime hours of Thursday, the showers and storms that develop overnight will likely end with VFR weather expected. Another round of heat of the day showers and storms will be possible during the afternoon 18z-22z. && .MARINE... Issued at 400 AM EDT Thu Sep 3 2026 The surface pattern remains fairly benign the next few days with lighter synoptic scale winds expected. Winds should remain at or below the 5-15 knot range which will result in waves of 2 feet or less through Saturday. No advisory level wave events are expected. The one item to keep an eye on though is the threat of thunderstorms and stronger winds associated with them. We will be in a pattern conducive for storms and wind today. Winds and waves can obviously be higher in and near thunderstorms and mariners will need to remain alert to this threat. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion