905 FXUS63 KGRR 231849 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 249 PM EDT Thu Jul 23 2026 .KEY MESSAGES... - Dry through Saturday morning - Periods of showers/storms possible Saturday night into Tuesday - Temperatures warming into Sunday/Monday && .DISCUSSION... Issued at 248 PM EDT Thu Jul 23 2026 - Dry through Saturday morning High pressure will dominate the area weather tonight through Saturday morning. Vertical profiles show a distinct lack of moisture through that time outside of some occasional cumulus level moisture. We are looking at mostly clear to partly cloudy conditions through Saturday morning. Lows in the 50s and highs around 80 will be common through Saturday. - Periods of showers/storms possible Saturday night into Tuesday The first question during this period is when do showers and thunderstorms first make it back into the forecast. It still appears to be Saturday night, but there is a push of moisture and therefore MUCAPE into Southwest Lower Michigan Saturday afternoon and evening. The NAM is more bullish on this, but even the ECMWF and GFS have MUCAPE values into the 500-1000 j/kg range. PWATs surge to 1.5+ inches during the same time. We will be watching this time frame closely as many have summer activities going on. The pattern from Saturday night through Tuesday is dominated by northwest upper flow between a Plains ridge and a low centered near Hudson Bay much of the time. Low level moisture will be back in place which will make periodic thunderstorms possible each forecast period. Trying to nail down the more likely periods for showers and storms is the challenge. The two main focus periods are Sunday afternoon and evening and again Monday afternoon and evening. The upper shortwaves are subtle but it appears the Monday wave may be the stronger one. The ECWMF with the Monday wave produces a fairly deep surface low, sweeping a 994mb low through the Great Lakes. Mid level flow surges above 50 knots at times as well. So, at this point it looks likely that we will see periodic storms during this period with the threat of severe weather as well. Sunday and Monday would be the two highest likelihood days for the potential of strong to severe storms. Locally heavy rain will be possible as well given mid summer moisture in place. - Temperatures warming into Sunday/Monday Temperatures will warm from around 80 today and Friday to around 90 Sunday into Monday. 850mb temperatures warm to around +22C on Monday. The warm temperatures will combine with summer moisture to produce max apparent temperatures into the 90s. The highest apparent temperatures surge to 98 in the southeast CWA near Jackson on Monday. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 203 PM EDT Thu Jul 23 2026 VFR conditions will dominate the pattern through the forecast period. Still expecting winds to go calm this evening. Will will mix out tomorrow morning but should remain 5 kts or less. && .MARINE... Issued at 248 PM EDT Thu Jul 23 2026 High pressure is centered over the Great Lakes this afternoon and will remain in place through Friday afternoon. Friday night into Saturday the high slides off to the east and southwest return flow begins on the backside of the high. Winds and waves will be sub advisory level through Friday. In the return flow we could flirt with Beach Hazard Statement and Small Craft Advisory levels from about Whitehall to the north. At this point, we are thinking 2-4 feet and a moderate swim risk, but we will be watching. Southern zones, south of Grand Haven, should see more of a 1-3 foot on Saturday. Sunday afternoon and evening could be another time frame where winds and waves are up in southwest flow and aided by thunderstorms. Thunderstorms will pose a hazard to mariners and beach goers alike periodically from Saturday night into early next week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...Ceru MARINE...Duke

NWS GRR Office Area Forecast Discussion