866 FXUS63 KGRR 151901 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 301 PM EDT Mon Jun 15 2026 .KEY MESSAGES... - Showers and storms with a chance for severe Tuesday - More organized convection Wednesday with heavy rainfall possible - Unsettled weather pattern continues && .DISCUSSION... Issued at 259 PM EDT Mon Jun 15 2026 - Showers and storms with a chance for severe Tuesday The forecast remains fairly consistent. An upper level node will swing through the Great Lakes tomorrow. Corresponding mid level trough will aid in instability. The strong gradient will allow for strong southerly flow throughout the day. While temperatures remain cooler than normal, with dewpoints only in the 60s, any sunshine will aid the 1K J/kg of CAPE. Latest ensembles chances for several lines to move through. First one will be fairly weak and if the atmosphere remains unstable there is a better chance for strong to severe storms early Tuesday evening. Shear remains nominal but there is some signal for better shear as the mid level trough moves overhead after 22Z. - More organized convection Wednesday with heavy rainfall possible The upper level low situated over central Canada is the weather system that is driving the weather pattern this week. It is the system that the above mentioned node is moving off of. Another short wave will move through the Midwest and then the Great Lakes on Wednesday. The difference from Tuesday`s system is that it has better moisture and a closed low in the mid levels and at the surface. With this better organization it has stronger winds and shear and thus a better chance at producing severe weather. However, there remains some questions on timing and position. The negatively tilted trough off the 850mb low will bring a frontal system through late Wednesday. Out ahead of that frontal system is approx. 1 to 2 inches of QPF. Given that amount of weather, along withe the instability warrants the slight risk that SPC has along and south of the I 94 corridor for Michigan. Will need to hone in on timing but damaging winds will be possible late Wednesday. As heavy rainfall is likely, localized flooding Wednesday evening will be possible. - Unsettled weather pattern continues The upper level low over Canada will slowly move eastward but will continue to cycle cooler and wetter weather through the area through the rest of the week. This will keep temperatures below normal and keep chances for rain this week, especially the upcoming weekend. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 124 PM EDT Mon Jun 15 2026 Diurnal cu has developed downwind of the lake shadow, but will dissipate with sunset. Generally clear overnight. A cold front will approach from the west Tuesday morning and scattered showers are possible. && .MARINE... Issued at 259 PM EDT Mon Jun 15 2026 The strong westerly flow from last evening is slowly subsiding this afternoon. That flow had caused 2 to 5 foot waves to the lakeshore between Saugatuck and Pentwater. Waves at Grand Haven and Holland continues to have near 5 footers this afternoon. Waves will continue to slacken as the afternoon continues and into the early evening. Strong southerly flow will move in tonight bringing strong southerly winds. Those winds and waves will bring another round of SCA conditions with widespread beach hazards through Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ050- 056-064. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ845>847. && $$ DISCUSSION...Ceru AVIATION...04 MARINE...Ceru

NWS GRR Office Area Forecast Discussion