551 FXUS63 KGRR 051102 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 702 AM EDT Fri Jun 5 2026 .KEY MESSAGES... - Periods of Showers and Thunderstorms Through Saturday - Additional Chances for Showers and Thunderstorms Monday Night into Wednesday - Building Heat Mid to Late Next Week && .DISCUSSION... Issued at 313 AM EDT Fri Jun 5 2026 - Periods of Showers and Thunderstorms Through Saturday The shortwave trough currently supporting thunderstorm development in Missouri will gradually shift east today into Saturday bringing multiple rounds of showers and thunderstorms to the area. Instability will initially be lacking, so not expecting any thunder this morning. Showers will move in along the lakeshore this morning and slowly expand eastward through the day as multiple rounds of positive vorticity advection spark off showers along with convergence with the low level jet. The low level jet will build over the area before starting to shift east this evening. Instability will also build through the day. HREF Mean MUCAPE peaks around 1000 J/kg this evening mainly south of I-96. With our best instability not lining up with the low level jet and best shear our potential for severe storms has decreased. Therefore the latest SPC outlook has dropped the marginal risk over our area. However with precipitable water values approaching 2 inches and saturated soundings expect some decent rainfall rates. The initial round of rain plus any additional storms that develop overnight will bring rainfall amounts around a quarter of an inch to an inch with isolated spots of 2 or more inches highlighted by the localized probability-matched mean of the HREF. Showers and storms will become more scattered late tonight with another round of positive vorticity advection moving through. This should clear by daybreak Saturday morning. We`ll then need to watch for additional thunderstorms to develop before the cold front moves through. Timing isn`t ideal, but there is a chance for strong to severe storms mainly along and east of a Kalamazoo to Lansing line Saturday afternoon. Instability is a bit better tomorrow with values 1000 to 1500 J/kg and shear of 30 to 40 knots. Damaging winds are the main risk with any stronger storm, but can`t completely rule out some quarter sized hail. - Additional Chances for Showers and Thunderstorms Monday Night into Wednesday An upper level ridge builds in for Sunday into Monday bringing a period of dry weather. Chances for showers and thunderstorms then increase Monday night into Tuesday with the best chances (greater than 60 percent) Tuesday afternoon. This is due to the feature currently over Mexico being absorbed into the mid level flow and moving northeast into Michigan. Rain chances could linger into Wednesday, but that depends on how Tuesday`s system tracks. Otherwise dry conditions return for Thursday and Friday. - Building Heat Mid to Late Next Week With the previously mentioned upper level ridge temperatures are expected to warm throughout the week by a few degrees each day. Temperatures are expected to start out in the low to mid 80s Sunday and warm into the upper 80s to mid 90s by the end of next week. We`ll need to monitor for heat indices of 100 or more. Welcome to summer. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 700 AM EDT Fri Jun 5 2026 Rain will slowly move into the area this morning through the afternoon with the potential for thunderstorms largely after 18Z and continuing into the evening. Heavy rainfall, reduced visibilities, and lightning are the main concerns with thunderstorms today. The potential for strong to severe storms is low. Ceilings will gradually lower through the day to MVFR/IFR levels by 6Z tonight. Southwest winds will pick up with gusts around 25 knots through the day. Winds become lighter overnight with isolated storms possible late tonight into Saturday morning with the best potential along and south of a AZO to JXN line. && .MARINE... Issued at 313 AM EDT Fri Jun 5 2026 South to southwest winds pick up today with gusts 20 to 25 knots. Highest gusts will likely be observed right along the lakeshore. With the building winds, wave heights will increase this morning with 4 foot waves more likely near and north of Grand Haven. It is in these areas as well that we expect a moderate to high swim risk with the most dangerous swimming conditions on the south side of piers and breakwalls. Along with the gusty winds and waves rain moves in this morning and could reduce visibilities. Thunderstorms become more likely this afternoon with chances lingering through tonight. Winds become lighter tonight into Saturday and shift to the northwest late Saturday afternoon. Thunderstorms will remain possible through Saturday morning. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through this evening for MIZ037-043-050- 056. MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849. && $$ DISCUSSION...RAH AVIATION...RAH MARINE...RAH

NWS GRR Office Area Forecast Discussion