484 FXUS63 KGRR 071845 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 245 PM EDT Mon Sep 7 2026 .KEY MESSAGES... - Showers/storms likely Tuesday night into Wednesday - Rain possible Saturday - Stronger system possible Monday with rain and wind && .DISCUSSION... Issued at 245 PM EDT Mon Sep 7 2026 - Showers/storms likely Tuesday night into Wednesday High pressure continues in control of the weather this afternoon with seasonable temperatures for early September and much lower humidity levels compared to last week. This drier weather will continue through most of the day Tuesday for most areas. Very late on Tuesday, the rain chances will begin to increase across the NW corner of the area, with rain spreading SE through Wednesday morning. This increase in rain chances will be via a 30+ knot low level jet advecting decent moisture ahead of the incoming cold front. The thunder threat looks to be a scattered to numerous one with fairly low chances of anything severe. The low level jet moving in will provide enough elevated instability Tuesday night for thunder. It is not very strong, only around a few hundred J/kg at best. This is due to the timing of the front approaching during the coolest time of the day, and with a lack of support aloft from a cold pool/short wave. Showers and storms will be most likely in the morning, then gradually moving out from NW to SE during the afternoon hours. This is a bit too early for any significant destabilization to occur during peak heating. We can`t rule out an isolated shower on Thursday afternoon as a weak upper trough will be moving through. This trough could combine with some lake breeze convergence to pop a shower or two. The vast majority of the area and day will be dry. - Rain possible Saturday High pressure will be over the area Thursday night and Friday, before shifting east of the area Friday night. There is a short wave moving into Ontario that will drag another cold front into the area on Saturday. This front looks to have much less rain potential with it for multiple reasons. The first is that the upper support once again stays north of the area, limiting the upper level synoptic support. In addition, the front does not have a good strong moist flow ahead of it from the Gulf. If anything, the trend in the data has been for less and less rain to be expected. - Stronger system possible Monday with rain and wind We see a brief break on Sunday before the next system approaches on Monday. This system has the potential to be a much stronger system than the two systems earlier in the period. We will see a stronger upper low drop into the Pacific NW by next weekend. It will then rotate eastward across the northern tier of the country late next weekend into early next week. It is expected to support a stronger sfc low over the Upper Midwest that will be driven ENE, and approach the region. We could see the initial rain with this system as early as late Sunday night into Monday morning with a leading short wave, and/or the warm air advection low level jet supporting the chances. Then, after a period of potentially being in the warm sector, the cold front will move in fairly strong. This system looks like right now that it will have a favorable feed of rich Gulf moisture ahead of it. Of course details with regard to timing and exact track this far out are still uncertain. This system could cause some impacts with rain, storms, and wind. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 158 PM EDT Mon Sep 7 2026 Afternoon cumulus clouds at or above 4,000 feet will dissipate around sunset. There is a slight chance of patchy fog early Tuesday morning, though it may be kept in check by 15 knot winds at 500 feet. &&245 .MARINE... Issued at 245 PM EDT Mon Sep 7 2026 No marine headlines will be needed until likely late Tuesday. High pressure over the area this afternoon is bringing light winds and low waves. Winds will increase on Tuesday, likely hitting Small Craft Advisory criteria late in the day with the stronger winds ahead of the front. These conditions will then likely last through most of Wednesday on the back side of the front with the cooler air moving in. We will see a lull in the higher winds/waves then late Wednesday through most of Friday. We could be looking at headlines being needed Friday night and Saturday in association with the next system moving through. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...NJJ AVIATION...CAS MARINE...NJJ

NWS GRR Office Area Forecast Discussion