FXUS63 KGRR 270654 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 254 AM EDT Sat Jul 27 2024 .KEY MESSAGES... - Increasing Heat and Humidity Into Sunday Afternoon - Potential for Showers and Thunderstorms Monday and Tuesday && .DISCUSSION... Issued at 254 AM EDT Sat Jul 27 2024 - Increasing Heat and Humidity Into Sunday Afternoon A mid level ridge and surface high pressure remain rooted over the state through a good chunk of the weekend. Dry and stable air will result in typical mid-summer weather conditions including cloud free skies with relatively light winds. Temperatures in the low to mid 80s today, then the heat turns on Sunday with highs in the upper 80s. Southerly return flow ushers in moisture Sunday afternoon increasing humidity levels later in the day. Rain chances increase for far southwest lower MI late Sunday. - Potential for Showers and Thunderstorms Monday and Tuesday The mid to upper level wave of low pressure down in TX lifts up into the Great Lakes Region Monday. While this system lifts northeast of the area on Tuesday, another wave digs in from the northwest Tuesday. Instability peaks in the afternoon both days, especially inland. Ensemble PWAT values have trended up during this timeframe with mean values in the 1.75 to 2.00 inch range. The 0-6km bulk shear values remain relatively low so organized severe weather looks unlikely. The main impact from the mainly afternoon evening convection will be for locally heavy rainfall. We will continue to highlight both days with high afternoon/evening POPs for inland locations. WPC does have the region in the day 4(Tuesday) excessive rainfall outlook with a marginal risk. Beyond Tuesday there's still a decent amount of uncertainty in terms of how much shower/storm activity we will see. The ECMWF is showing a mid level low trying to cut off as it drops in from the northwest towards Friday. The Canadian and GFS keep moving this system along. PWAT's remain high and instability peaks in the afternoon/evening hours. There is a lot of spread in ensemble qpf values for the end of the week. For now we will feature typical isolated/scattered afternoon convection for the region. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 120 AM EDT Sat Jul 27 2024 High pressure centered over Lower MI shifts east of the region today. South to southeast flow will start to develop over the region today, but overall the pressure gradient remains weak. Most of the time the wind will remain under 10 knots. Moisture advection does not increase until Sunday, so for now we will keep the cloud cover limited. Patchy fog could once again develop just prior to daybreak, but based on the latest model trends, the potential is too low to include it in the forecast for now. && .MARINE... Issued at 254 AM EDT Sat Jul 27 2024 No major marine concerns are anticipated through the weekend. Southerly winds will stay light under high pressure today and will increase slightly Sunday and Monday. Waves will stay to 2 feet or less through the early half of next week. Overall, winds and waves stay below headline criteria through Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...MJS/Thielke AVIATION...MJS MARINE...Thielke