745 FXUS63 KGRR 041049 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 649 AM EDT Sun Oct 4 2026 .KEY MESSAGES... - Brief Period of Rain this Morning - Areas of Frost Possible Tonight and Monday Night && .DISCUSSION... Issued at 222 AM EDT Sun Oct 4 2026 - Brief Period of Rain this Morning A shortwave trough is moving through this morning with plenty of positive vorticity advection and 700 mb frontogenesis. These showers are elevated as seen in observations with cloud bases around 8 to 10 kft. As radar trends continue it looks like most will see light rain before the 850 mb front clears around 9am. Dry conditions are expected through the remainder of the forecast, but Tuesday night into Wednesday will need to be monitored. A decent low level jet, warm air advection ahead of the shortwave trough and front will be present. The question is will there be enough moisture. Currently better chances are north of the area, but the ENS members highlight light rain across the forecast area. If this trend continues, chances for precipitation will need to be added. - Areas of Frost Possible Tonight and Monday Night High pressure builds in tonight and continues into Monday. 925 mb temperatures will fall into the 6 to 8 C range. The inversion that develops isn`t overly strong so expecting inland areas along and north of U-10 to have the best chance for lows dropping into the mid 30s with isolated colder spots. However confidence is not high at this time as there has been a slight warming trend in the data. In coordination with Gaylord held off on issuing a Frost Advisory at this time due to the uncertainty. Monday night will have a better chance for more widespread frost as low temperatures drop into the mid to upper 30s across areas largely east of US-131 and north of I-96. The best chances (50 percent) for lows in the low to mid 30s will be inland areas along and north of US-10. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 649 AM EDT Sun Oct 4 2026 Rain will move out of the area over the next hour. Can`t rule out a stray rumble of thunder south of Lansing and near Jackson. Otherwise southerly winds today will gradually shift to the west and then northwest this morning and afternoon as the front moves through. Gusts this afternoon are expected to be around 20 knots. Lighter northwest winds develop tonight into Monday morning. && .MARINE... Issued at 222 AM EDT Sun Oct 4 2026 Winds will pick up from the southwest as this morning`s rain clears and then shift to the west and northwest during the late morning and afternoon. Waves build into the 4 to 7 foot range north of Holland with the highest waves north of Muskegon. Gusts around 20 to 25 knots may linger longer into tonight for areas north of Grand Haven. Additionally waves may approach 4 feet near and south of South Haven. Therefore the Small Craft Advisory will likely need to be adjusted for this evening into Monday morning. Another period of Small Craft Advisory conditions looks to develop Tuesday with strong southwesterly winds. There is the potential that a brief period of gales develops towards Little and Big Sable Tuesday afternoon. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ846. Small Craft Advisory until 8 PM EDT this evening for LMZ847>849. && $$ DISCUSSION...RAH AVIATION...RAH MARINE...RAH

NWS GRR Office Area Forecast Discussion