


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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134 FXUS63 KGRR 271752 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 152 PM EDT Fri Jun 27 2025 .KEY MESSAGES... - Hot, Humid, and Thunderstorms Today - Drier Over the Weekend - Chances for Showers and Storms Return Next Week && .DISCUSSION... Issued at 326 AM EDT Fri Jun 27 2025 - Hot, Humid, and Thunderstorms Today Our current line of showers and thunderstorms is expected to exit east of the area by daybreak, meanwhile behind the line isolated showers and storms are possible. Additionally showers over Lake Michigan and Wisconsin associated with outflow boundaries and positive vorticity advection ahead of the 500mb trough axis will move in early this morning providing another focus for showers and storms. Not expecting any severe storms with this mornings convection, but could see some strong to severe storms this afternoon mainly along and south of a Kalamazoo to Lansing line. This is due to the slow moving front allowing instability around 2000 to 3000 J/kg to build ahead of it. We`ll be on the backside of the 500mb jet of 30-40 knots providing some upper level divergence. Sounding profiles support the potential for strong winds, especially the farther east you go. This is also supported by various machine learning guidance and the updated SPC outlook. Thunderstorms look to exit the area by the early evening with dry conditions expected overnight. Precipitable water values still remain high toward 2 inches. As seen over the past few days 1 to 2 inch per hour rainfall rates are possible and could cause some minor flooding in urban areas and known trouble spots. Lastly it will be another hot and steamy day until the front moves through, especially along and south of that Kalamazoo to Lansing line. Heat indices will be in the 90s for much of the area with some spots approaching 100. With only isolated spots possibly hitting 100 due to thunderstorms and cloud cover, held off on any Heat Advisory. - Drier Over the Weekend Drier conditions are expected over the weekend, with a cooler day for Saturday with highs in the 70s to low 80s and heat indices matching air temperatures. Temperatures warm up once more for Sunday with highs in the upper 80s to low 90s ahead of our next chance for rain. Heat indices in the mid to upper 90s are expected. - Chances for Showers and Storms Return Next Week Our next chance for rain and thunderstorms arrives Sunday night into Monday as a shortwave trough moves through. Additional shortwave troughs move through each night through Wednesday night. Most of the long range ensemble members are dry though after rain exits the area Monday with the drier air in place. Therefore kept the NBM POPs of less that 20 percent, but will need to monitor if moisture improves within these shortwaves. After Monday, temperatures look a bit more comfortable with highs in the 80s and lows in the 50s and 60s. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 148 PM EDT Fri Jun 27 2025 Showers and storms are the concern for the early part of the period. Radar shows developing storms ahead of a cold front. These storms should miss MKG and probably GRR, but we`ve included a TEMPO for the other terminals for a few hours later this afternoon. The threat should pass from west to east by early evening leading to a broken VFR cloud deck. && .MARINE... Issued at 326 AM EDT Fri Jun 27 2025 Southerly winds are expected with isolated showers and storms possible this morning and early afternoon. Winds become more west to northwesterly late this afternoon and overnight behind a cold front. High pressure Saturday will keep winds light and variable before shifting to the south Saturday night into Sunday as the high shifts east. Southwest winds build during the day Sunday and may approach Small Craft Advisory conditions during the afternoon. Waves however look to remain in the 1 to 3 foot range into next week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...RAH AVIATION...04 MARINE...RAH