598 FXUS63 KGRR 011042 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 642 AM EDT Fri May 1 2026 .KEY MESSAGES... - A few showers today; Freeze tonight - Mostly dry Saturday through Monday - Wet system Monday night-Tuesday; Unsettled and cool next week && .DISCUSSION... Issued at 227 AM EDT Fri May 1 2026 - A few showers today; Freeze tonight We continue to see a lot of small features driving the forecast with the upper low complex in charge, and weak waves rotating around it. One of these waves is currently responsible for the band of light rain along the I-94 corridor this morning. The wave itself is south of the state line, with the deformation zone barely sneaking up over our far southern area. This rain will move out by daybreak this morning. The upper flow remains cyclonic today with multiple weak short waves moving through. The hi-res models indicate that a weak one coming from Wisconsin will touch off a few light showers over the lake and spread inland this morning. Then, diurnal heating combining with another wave coming in will pop isolated to scattered showers inland this afternoon. These will then dissipate mid evening and allow skies to clear out quite a bit. This clearing combined with dew points in the 20s are setting up the night for a good freeze potential for most of the forecast area, with the coldest across the interior portions of Central Lower. With Frost/freezing conditions up north this morning, coordination with neighboring offices supports holding on to the headlines as is right now to limit confusion. - Mostly dry Saturday through Monday While most areas will stay dry Saturday, there remains about a 15 percent chance of a shower popping up along the lake breeze Saturday afternoon. The cyclonic flow will slip east of the area later Saturday. Hi-res models are indicating an isolated shower popping along the lake breeze. Inversion heights coming down will help to limit shower development, but not completely with some forcing/convergence to assist. Again most of the area should be dry on Sunday, but northern areas have a chance of some light rain. We get out from under the cyclonic flow, but a short wave will ride just close enough to us over the U.P. to help fire a few light rain showers. The southern portions of the area should remain dry. High pressure at the sfc and weak broad ridging aloft should keep most of the area dry on Monday. It may be close late Monday as the cold front approaches, and moisture gets close coming in from the Gulf. - Wet system Monday night-Tuesday; Unsettled and cool next week The system coming in on Monday night will be facilitated by the next long wave upper trough diving SSE from Western Canada. As this trough dives SE, it will be able to tap some better moisture that will be in place already just south of the state. The better moisture, somewhat warmer air ahead of the front could produce just enough instability to allow for a rumble or two of fire. The general theme of the weather from Tuesday through Thursday next week will be once again cool and uncertain with regards to timing of waves and any details with them. It does look like we end up back under cyclonic flow, and periodic shower chances on and off through the period with any embedded wave that moves around the upper low. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 642 AM EDT Fri May 1 2026 No major changes needed from the 06z forecasts. The light rain along the I-94 corridor has moved out, leaving mainly mid clouds in its wake. There has been some isolated stratus at KJXN around 500-700 ft, so added a tempo for that until 14z. Mid clouds will hang around, and a few showers will develop inland from the lake after 16z. These should be light and few and far between, so went with VCSH and VFR conditions for these. We will scatter out later this evening with a light wind from the NW remaining. && .MARINE... Issued at 227 AM EDT Fri May 1 2026 We continue to watch this afternoon for a possible marginal SCA event with the building ridge coming in and squeezing against the lower pressure over land due to heating. At this time, it looks too marginal to issue the headline. The first half of the weekend will see tranquil conditions with high pressure nearby. We will see winds and waves build Saturday night into Sunday as we start to see return flow on the backside of the ridge. SCAs are likely going to be needed for Saturday night and Sunday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Frost Advisory until 8 AM EDT this morning for MIZ037-043>046- 051-052. Freeze Watch from late tonight through Saturday morning for MIZ037>040-043>046-050>052-056>059-064>067-071>074. Freeze Warning until 8 AM EDT this morning for MIZ038>040. MARINE...None. && $$ DISCUSSION...NJJ AVIATION...NJJ MARINE...NJJ

NWS GRR Office Area Forecast Discussion