518 FXUS63 KGRR 261837 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 237 PM EDT Sun Jul 26 2026 .KEY MESSAGES... - Isolated Severe Storms Possible Today and Tonight, Large Hail and Damaging Winds Possible. Timing and Coverage Is Uncertain. - Severe thunderstorms possible Monday afternoon/evening. Damaging winds are the main risk with all hazards possible. Timing and coverage remain uncertain. - Cooler With Chance of Showers Friday && .DISCUSSION... Issued at 236 PM EDT Sun Jul 26 2026 - Isolated Severe Storms Possible Today and Tonight, Large Hail and Damaging Winds Possible. Timing and Coverage Is Uncertain. Low (10-20%) chance of isolated thunderstorm development near and east of US127 this afternoon as eroding MLCIN couples with an approaching shortwave. However, a lack of any kind of mesoscale forcing/surface boundary should limit storm development. Ample DCAPE with 30-45 knots of deep layer shear and around 1000 J/kg MLCAPE could support storm organization with damaging winds as the main hazard and large hail also possible. Attention then turns to a mid-level wave across the Northern Plains as seen in satellite imagery. This wave is forecast to initiate storms later today across northern Wisconsin and Minnesota. These storms are forecast to propagate southeast along the instability gradient. Two scenarios remain possible as of this package. First is that the storms take a more southerly track remaining over Lake Michigan. Second is the instability makes it a bit further east allowing one or more clusters with embedded bowing structures to impact the CWA, best chance near and west of US-131. Short range guidance is split on which scenario occurs, with mesoscale analysis into the evening being critical for identifying which scenario occurs. Large hail and damaging winds are the main threats. Greatest risk window is 10pm tonight through 6 am Monday. Bottom line is strong to severe storms are possible today and tonight, greatest risk west of US-131. However, depending on storm track, many areas could stay dry through tonight or see just garden variety showers and storms. - Severe thunderstorms possible Monday afternoon/evening. Damaging winds are the main risk with all hazards possible. Timing and coverage remain uncertain. The aforementioned convective uncertainty carries over into the forecast for Monday afternoon and evening as debris clouds and or boundaries from earlier storms will affect the degree of destabilization by evening as well as potential locations for storm initiation. Short range model guidance does paint a potent environment for Monday evening as lower Michigan sets up in the left exit region of a mid-level jet. This will lead to over 50 knots of deep layer shear across West Michigan. Storms are forecast to initiate off a surface trough/cold front Monday evening and track southeast with time. If the forecast destabilization occurs, a very favorable environment will be in place for thunderstorms to be severe. Strong kinematics and north of 1200 J/kg DCAPE supports a damaging wind threat with concern for winds in excess of 70 mph in any bowing structures that may materialize. Initial development given the kinematics at play likely is supercellular if a favorable environment is realized. Strong shear could support large hail in discrete storms as well. In addition, can`t rule out a tornado or two southwest of a Muskegon to Jackson line. However, uncertainty persists in the strength of the LLJ and associated low-level shear available Monday evening. Overall, we have a conditionally favorable environment for severe weather (possibly significant) Monday evening. If we have a favorable thermodynamic environment, severe weather is possible areawide, especially the southern 2/3 of the forecast area. However, this setup will come down to mesoscale details with a chance that overnight storms limit intensity/development of storms Monday evening. With a range of potential solutions still present across guidance, the forecast remains uncertain and changes are very possible into Monday. - Cooler With Chance of Showers Friday Post cold-frontal conditions are likely to see slightly cooler conditons as well as dewpoints falling back into the 60s. Troughing aloft, a dry low-level airmass, and surface ridging are likely to keep conditons dry until mid-week. A frontal boundary and attendant shortwave Friday then bring a chance of showers back to the area to finish the work week. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 145 PM EDT Sun Jul 26 2026 Low clouds continue to linger with MVFR cigs at BTL and periods of such at AZO. These low clouds will fade as the day continues. The big question will be the timing of the storms this evening and into Monday morning. There are two waves of showers and storms expected through the TAF period. The first of which is expected roughly between 02Z and 08Z. The second of which is between 09Z to 14Z. The environment is favorable for storm development so will probably be timing this out for TEMPO groups in the next set of TAFS. Based on confidence and timing concerns have gone PROB30 for now. The airports that are most likely to see VCTS or TSRA are MKG, GRR, AZO and BTL. JXN and LAN should see showers but are on the edge for storms for either of these waves. && .MARINE... Issued at 236 PM EDT Sun Jul 26 2026 First, have issued a Marine Dense Fog Advisory for the nearshore north of Holland. Webcams indicate the higher dewpoints are causing areas of dense fog across this region with short range guidance suggesting these conditons continue into the overnight hours. Second, both late this evening into Monday morning and again Monday evening, thunderstorms are possible across the waters. Coverage, location, and track of any storms remains uncertain at this stage. However, thunderstorms will be capable of locally higher waves and winds over 34, potentially over 50 knots. Third, southwest flow of 10-15 knots is expected today and tomorrow ahead of a cold front keeping waves below hazardous levels. Northwest winds behind the front then increase to near 30 knots Tuesday into Wednesday, with hazardous waves expected to develop as a result. A Small Craft Advisory and Beach Hazards Statement will likely be needed as we get closer. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Dense Fog Advisory until 2 AM EDT Monday for LMZ846>849. && $$ DISCUSSION...Thomas AVIATION...Ceru MARINE...Thomas

NWS GRR Office Area Forecast Discussion