069 FXUS63 KGRR 221117 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 717 AM 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 /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 717 AM EDT Wed Apr 22 2026 Local MVFR to IFR visibility from patchy fog will improve around 13 Z. Moisture will be greater during the day in southern Michigan, so AZO, BTL, and JXN have a chance of afternoon isolated/scattered thunderstorm cells based on some runs of the latest short-term models. Confidence is low as this is a recent uptrend in probability, and not all models place thunderstorms this far north, as the chance of thunderstorms is more favored to the south in Indiana and Ohio. Patchy fog may redevelop late tonight. && .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...CAS MARINE...CAS

NWS GRR Office Area Forecast Discussion