450 FXUS63 KGRR 131735 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 135 PM EDT Sun Sep 13 2026 .KEY MESSAGES... - Slight chance of Rain Today - Showers and Thunderstorms Possible Tuesday through Thursday && .DISCUSSION... Issued at 216 AM EDT Sun Sep 13 2026 - Slight chance of Rain Today A cold front moves through today along with some mid-level frontogenesis. Moisture is limited however and POP have trended lower since yesterday. Best chance for rain will be across the central forecast area this afternoon. Cooler and drier air moves in behind the front. With the surface high building in tonight, radiational cooling conditions will be optimized and temperatures will fall into the 40s in most places, with even upper 30s possible across the northern interior. - Showers and Thunderstorms Possible Tuesday through Thursday A shortwave trough ejects out of the northern Rockies with a surface low tracking into Canada by Tuesday. A trailing cold front is expected to touch off showers and thunderstorms Monday night and Tuesday. Instability and deeper moisture is across northern Lower Michigan pooling ahead of the cold front, which sinks south through the forecast area on Tuesday. Precipitable water surges close 2 inches, so heavy rain potential is there as the front will be moving slowly and MBE vectors are less than 5 knots. The front stalls across the southern zones on Wednesday, with a showers and thunderstorms possible into Thursday as a surface low tracks along the front across southern Lower Michigan. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 130 PM EDT Sun Sep 13 2026 VFR conditions will prevail through the TAF period at all TAF sites. Mid clouds /bases 10-12kft/ will quickly increase next few hours, as a fast moving impulse moves W to E across the lower Great Lakes. This will also yield a small window of light showers, per upstream obs and short range model guidance, likely lasting no more than 1-2 hr at any given TAF site between roughly 19-00Z. Given dry air mass and high cloud bases, don`t expect vsbys in rain showers to drop below 6SM. Skies will then clear by early this evening, and continue for the duration of the night through 18Z Monday. NW breezes gusting to 15-20 kt this afternoon will quickly diminish to around 5 kt this evening as high pressure builds overhead, then become E/SE 5-10 kt early Monday as high slowly moves east of the area. && .MARINE... Issued at 216 AM EDT Sun Sep 13 2026 No changes to the marine headlines. After a brief lull, winds and waves will increase again on Monday night and Tuesday when south gales are expected. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until 11 PM EDT this evening for MIZ037- 043-050-056-064-071. MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849. && $$ DISCUSSION...Ostuno AVIATION...Smith MARINE...Ostuno

NWS GRR Office Area Forecast Discussion