520 FXUS63 KGRR 111910 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 310 PM EDT Sat Apr 11 2026 .KEY MESSAGES... - Showers and Storms with Increasing Flood Concern Sunday - Possible Severe Thunderstorms and Flooding Mon Night and Tue && .DISCUSSION... Issued at 310 PM EDT Sat Apr 11 2026 - Showers and Storms with Increasing Flood Concern Sunday Rain is expected to develop late tonight with moisture brought by a 850-700 mb jet north of an advancing warm front. Instability will be relatively meager but increase just enough for some lightning beginning during the early morning hours of Sunday. The longer-duration rain and heavier totals are more favored north of I-96 toward central and north-central Lower Michigan, with a chance of showers/storms persisting throughout much of the day in that area. Southern locations which are more likely to break into the open warm sector during the day with a few breaks in the clouds may have a period of gusts 30-40 mph as temperatures surge into the 70s. Mesoscale models depict a fairly robust convectively enhanced shortwave ejecting out of TX/OK as nearly a closed low Sunday which will provide an additional impetus for rain and spotty thunderstorms in Lower Michigan Sunday evening into Monday morning. The 12Z HREF probability matched mean rainfall totals through Monday morning paint a large area of 1.5 to 2.5 inches north of Muskegon, Grand Rapids, and Alma. This is higher than the official forecast of about 1 to 1.5 inches. Fortunately rivers have crested and soil has at least had several days to dry out from the wet patten since the beginning of March, but unfortunately there is not much room to absorb additional rain. Minor areal and river flooding has the potential to return relatively quickly if a wetter scenario unfolds. - Possible Severe Thunderstorms and Flooding Mon Night and Tue A large plume of greater than 1000 J/kg of MUCAPE will spread over Michigan Monday night through Wednesday, and set up the potential for at least a couple rounds of thunderstorms as shortwaves move over a wavering frontal zone. SPC has highlighted Lower Michigan in a marginal risk for severe weather Monday night and a slight risk for Tuesday-Tuesday night. Precipitable water values expected around or above 1.25 inches wouldn`t be far from the climatological maximum for the time of year, making flooding a persistent concern this week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 136 PM EDT Sat Apr 11 2026 VFR conditions continue with easterly winds becoming more southeasterly tonight. The low level jet will also move into the region creating low level wind shear of around 40 knots through Sunday morning. Scattered showers will be possible late tonight into Sunday morning as well with the best chances (60 percent or greater) toward MKG and to the north. It is this area that ceilings are expected to dip to MVFR with only a 20 percent chance for IFR conditions at MKG Sunday morning into early Sunday afternoon. There could be some embedded thunderstorms within the showers but confidence was not high enough to include in the TAFs. && .MARINE... Issued at 310 PM EDT Sat Apr 11 2026 Southeast winds strengthen early Sunday morning, becoming south- southwesterly during the day. Waves will build throughout the day and stay hazardous to small craft through at least Monday morning. Scattered thunderstorms may develop above the cooler marine air on Sunday. Slight chance one Sunday evening could stir up the lower atmosphere enough to bring down a gale force wind gust. Additional hazards to small craft are likely Monday night through Tuesday from winds, waves, and chances for thunderstorms. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory from 4 AM Sunday to 4 PM EDT Monday for LMZ844>849. && $$ DISCUSSION...CAS AVIATION...RAH MARINE...CAS

NWS GRR Office Area Forecast Discussion