280 FXUS63 KGRR 221645 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1245 PM EDT Wed Apr 22 2026 .KEY MESSAGES... - Slight chance of afternoon shower or thunderstorm near I-94 - Showers and storms Friday afternoon and Friday night - Increasing confidence for rainy and breezy weather Mon-Tue && .DISCUSSION... Issued at 342 AM EDT Wed Apr 22 2026 - Slight chance of afternoon shower or thunderstorm near I-94 Patchy fog near and south of I-96 will mix out shortly after sunrise. Light winds are expected today, and it will be mostly sunny and dry in Central Michigan, while partly sunny with some daytime cumulus in Southern Michigan. Better low-level moisture pooled up in southern Michigan, especially near and south of Allegan-Jackson, is supporting an afternoon buildup of 500-1000 J/kg of mixed layer CAPE in some of the overnight CAMs. Capping may be weak and could be overcome with weak convergence along a subtle surface trough extending through Southwest Michigan, especially if there is a tendency for a weak mesoscale low to form along the trough as depicted in some models. Have introduced slight chance of thunderstorms near I-94 this afternoon, though somewhat higher chances exist to the south in Michiana. If a thunderstorm cell or two were to develop, isolated hail and gusty winds would be possible as cells propagate toward the east- southeast with a congealing cold pool in a lightly sheared environment. - Showers and storms Friday afternoon and Friday night The influence of a Northern Plains upper-level low (the left foot of an omega block pattern) is expected to nudge into Lower Michigan late Friday. Scattered showers and thunderstorms are expected in the vicinity of a frontal triple point passing through the area. CAPE and shear should be relatively modest, in the ballpark of 500-1000 J/kg and 20 knots, so the potential for severe storms is low. Rainfall amounts may broadly be 0.25 to 0.50 with isolated 1 inch possible. - Increasing confidence for rainy and breezy weather Mon-Tue A plurality of ensemble members solutions producing rain over Lower Michigan Monday into early Tuesday is now a majority. The southern branch of the upper level jet will strengthen over the Southwest US to south-central Plains, with a low developing in the exit region of this jet, making its way into the Midwest. Not clear if the track of the low will keep Michigan on the cool side or on the warm side, but there are plenty of members showing CAPE and generally breezy conditions with this low. This will have to be watched for thunderstorm potential, perhaps a nonzero threat of severe weather also. The median rainfall totals among the ensembles are a little higher with this system than with Friday`s, although naturally the spread is higher with some drier and some much wetter solutions also possible. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1245 PM EDT Wed Apr 22 2026 VFR conditions are ongoing and will continue through the evening. Isolated thunderstorms may develop near the I-94 terminals this afternoon/evening on a surface boundary with convective LLWS and lower visbys/cigs possible in any storm that develops. Will maintain the PROB30s and monitor for potential amendments if confidence grows. Tonight, clear skies and light winds will once again bring the potential for patchy fog. The worst conditions will be at AZO/BTL as low-level moisture comes in from the southeast. Any fog will dissipate after mid morning Thursday. && .MARINE... Issued at 342 AM EDT Wed Apr 22 2026 Light winds and low waves are expected today. Generally offshore flow this morning will become more onshore during the afternoon. Areas of fog may be present over the lake today into Thursday. Hazardous winds and waves for small craft will likely develop north of Grand Haven Thursday night into Friday with south winds. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...CAS AVIATION...Thomas MARINE...CAS

NWS GRR Office Area Forecast Discussion