FXUS63 KGRR 090740 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 340 AM EDT Fri May 9 2025 .KEY MESSAGES... - Dry and Mostly Sunny Through Monday, Slight Chance of Showers Saturday - Chances for Thunderstorms Middle to Late Next Week && .DISCUSSION... Issued at 340 AM EDT Fri May 9 2025 - Dry and Mostly Sunny Through Monday, Slight Chance of Showers Saturday High pressure will be largely over the region with mostly clear skies and warming temperatures through the weekend, though interrupted by a weak cold front on Saturday. Going with a slight chance of showers on Saturday... Models show a moist layer in the mid levels above the PBL, around 5,000 to 10,000 feet, which may be within a shallow conditionally unstable layer. As a result, a few higher-based, lower-topped showers could develop with enough rain that could survive the trip through drier air closer to the ground. - Chances for Thunderstorms Middle to Late Next Week Better moisture arrives Tuesday and sticks around for a few days. The NBM has dew points reaching the lower 60s. Average CAPE values among the ENS, GEFS, and CMC ensembles increase from Tuesday into Thursday or Friday, with a majority of members producing rain at some point during that time frame. Early next week, there is likely a split upper-level jet across the central US, with a broad ridge in the northern stream, and a cutoff low the southern US / Gulf region, forming a Rex block type of pattern. For Tuesday-Wednesday, the southern low should slowly migrate toward the Ohio Valley or southern Great Lakes. Scattered showers and thunderstorms should develop as a result, with a tendency for them to be more diurnally driven (occurring mostly during the afternoon). Wind shear appears rather weak, as do mid- level lapse rates. This should limit severe weather potential. Instead, deep moisture through the convective layer and slow- moving cells would favor localized downpours and highly variable rainfall totals. For Thursday-Friday, a deeper upper-level trough from the Dakotas approaches the western Great Lakes. Stronger surface fronts are expected, along with the potential for steeper mid-level lapse rates and increasing shear. This time frame would have some possibility for severe storms if this were to verify. It's still a week away, though confidence is a little higher than usual given low spread in the ensembles regarding the synoptic pattern evolution. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 135 AM EDT Fri May 9 2025 VFR expected today with clear skies. Winds will stay under 10 knots most of the time, from the northeast this morning, becoming more northwest or west during the afternoon. MKG winds will become west-northwest earlier as the lake breeze pushes in. && .MARINE... Issued at 340 AM EDT Fri May 9 2025 Light offshore winds this morning will become onshore during the day as a lake breeze develops. On Saturday, winds and waves may become hazardous to small craft, as north winds strengthen to 20-25 knots over mid Lake and near the Sable Points. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Freeze Warning until 9 AM EDT this morning for MIZ037>040- 043>046. Frost Advisory until 9 AM EDT this morning for MIZ050>052- 056>059-064>067-071>074. MARINE...None. && $$ DISCUSSION...CAS AVIATION...CAS MARINE...CAS