


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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770 FXUS63 KGRR 132302 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 702 PM EDT Sun Jul 13 2025 .KEY MESSAGES... - Heat Builds into Tuesday - Chances for Showers and Storms Midweek - Another Chance for Rain Potentially Next Weekend && .DISCUSSION... Issued at 221 PM EDT Sun Jul 13 2025 - Heat Builds into Tuesday Quiet weather will prevail from tonight into the day on Tuesday as high pressure drifts through the Great Lakes region. BUFKIT overviews show very little moisture in the profile. Some high clouds moving through the region today will shift southeast tonight and there will be some scattered cumulus development tomorrow, but that is it. No prospects for rain in the next 48 hours. Heat will build from today through Tuesday with high temperatures creeping up from the middle 80s today to around 90 on Tuesday. There is not a big increase in 850mb temperatures, but they are already warm. We actually stay between +16C and +18C through Thursday. So, upper 80s to around 90 the next couple of days. Mid week temperatures will be affected by convective clouds and precipitation. - Chances for Showers and Storms Midweek We could see some showers and storm leak into the area from the west Tuesday night, but the better bet is we remain dry Tuesday night as well. The focus is really on a weak boundary which will sag through the area in the Wednesday through Thursday night time frame. The best chances for showers and storms look to be both Wednesday afternoon and evening and again Thursday afternoon and evening. Obvious reason there are higher chances during that time is due to being at the diurnal peak, but also due to the fact that two separate shortwaves are forecast to be moving through the area at those times. We have likely chances for showers/storms (60 pct) during the afternoon/evening both days. Each day has some semblance of a low level jet with Wednesday having stronger winds. Each day has MUCAPE values around 2,000 j/kg potentially. In terms of deep layer shear it looks to be 20-30 knots so not overly strong but bad either. Potential for some stronger storms both days for sure, so we will be watching this time frame going forward. Precipitable water values eclipse 2.00 inches both days so locally heavy rain is certainly possible. - Another Chance for Rain Potentially Next Weekend There is model disparity with regard to a system next weekend. The ECMWF has a low moving through the Great Lakes Saturday night into Sunday, while the GFS is now beginning to trend some precip in as well. As we move forward the expectation is that both will likely have a system next weekend. Plenty of time to watch how the pattern evolves. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 700 PM EDT Sun Jul 13 2025 Diurnal cu is dissipating leaving high clouds and smoke over the region. VFR conditions and a light WSW wind is expected through the period. && .MARINE... Issued at 137 PM EDT Sun Jul 13 2025 A weak pressure gradient will continue through Tuesday, after which increasing southwest flow will begin to push waves higher from north to south. Swim risk at the lakeshore will remain low through Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT Monday night for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. MARINE...None. && $$ DISCUSSION...Duke AVIATION...04 MARINE...04