084 FXUS63 KGRR 061746 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 146 PM EDT Mon Sep 6 2021 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 328 AM EDT Mon Sep 6 2021 - Upper troughing with severe weather possible Tuesday && .DISCUSSION...(Today through next Sunday) Issued at 328 AM EDT Mon Sep 6 2021 After a fair weather Labor Day, we look to the risk of severe weather on Tuesday as an upper trough amplifies across the central Great Lakes with wind profiles showing 40 knots of deep layer shear. Strong unidirectional shear suggests storm type will favor linear, bowing segments. Any deep convection will be capable of wind damage given 50 knots progged to be near 5 kft AGL. A dry adiabatic subcloud layer will enhance downburst potential. Timing looks to be from mid-afternoon across the northwest forecast area to mid-evening by the time the storms clear the southeast sections near Jackson County. Synoptic wind gusts in the cold advection behind the storms could also gust over 40 mph. The storms could also build deep enough to produce large hail with forecast soundings showing CAPE through the minus 10C to minus 30C zone. The storms will be moving quickly so even if heavy rain rates materialize, flooding should be mitigated by storm speed. Fair and cool weather follows for Wednesday through Friday with overnight lows in the 40s in most places by Thursday morning and even some 30s are possible in the cold spots. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 146 PM EDT Mon Sep 6 2021 VFR will prevail through the forecast period. Winds will continue to gust towards 20 knots across the area before quickly weakening this evening, becoming calm overnight. Winds will then shift southerly early Tuesday morning while building. Gusts towards 25 knots or greater will be possible Tuesday afternoon with sustained winds around 10 to 15 knots. Very shortly after 18z Tuesday, a line of showers and storms will arrive from the northwest starting at MKG then will move southeast through Tuesday afternoon and evening. && .MARINE... Issued at 300 AM EDT Mon Sep 6 2021 Winds and waves will decrease this morning and we expect to let the Small Craft and Beach Hazards Statement expire at 8 am. Winds and waves will increase again on Tuesday and severe thunderstorms are possible in the afternoon. Conditions will remain hazardous through Wednesday as strong winds and high waves continue. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...Ostuno DISCUSSION...Ostuno AVIATION...Thielke MARINE...Ostuno