692 FXUS63 KGRR 120614 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 214 AM EDT Fri Jun 12 2026 .KEY MESSAGES... - Potential for severe weather remains for later this evening - Much cooler Friday; Rain chances return late Saturday into Sunday - Cooler and unsettled next week && .DISCUSSION... Issued at 304 PM EDT Thu Jun 11 2026 - Potential for severe weather remains for later this evening There has been a lot said over the past few days regarding the severe potential for tonight. That remains, but is still a little uncertain just a few hours out due to leftover showers and storms from last night trying to approach the area. The synoptic scenario generally remains unchanged with lots of dynamics still coming together over the area later this evening. The main uncertainty comes with the showers and isolated storms slow to diminish ahead of the main show, and the instability that can be realized with the strong dynamics. The showers and isolated storms are diminishing slowly as they approach Lake Michigan. A bit slower than just about all of the models have indicated. This is likely to delay the instability advection over the area ahead of the strong short wave driving the cold front through the region. An outflow boundary has settled over Northern Illinois. This is becoming stationary and is about to be pushed northward by the increasing low level jet ahead of the upper wave and sfc front. The bottom line is we expect plenty of instability to make it over the area with up to around 2500 J/kg, highest across the SW corner of the forecast area. The max instability will taper off as you head further north and west. Deep layer shear around 40 knots will work with the instability to provide organization to the storms that are expected to line up along the incoming cold front. Low level shear becomes very favorable with the low level jet ramping up, especially across the NW half of the forecast area. This along with backing winds at the sfc provides quite some impressive hodographs that would support the potential of isolated tornadoes along the QLCS. Forecast soundings indicate that the further north you go, the more of a stable layer is present. Further southwest, the stable layer is quite shallow, partially because of the front approaching before we lose too much instability, and partially because of the theta e axis ahead of the front. The mid level winds are also strongest over the western areas, leading to the best threat of strong winds. The best threat of damaging winds reaching the ground, and possible tornadoes will be there with the most shallow stable layer, with the threat diminishing the further north and east you go. The line should reach the Lake Michigan shore around 8-9 pm, and then clear the forecast area 12-1 am, ending the threat once it moves east. Some showers and storms may be possible with the wave upper wave lingering. but the rich instability will be gone. - Much cooler Friday; Rain chances return late Saturday into Sunday We will likely see some residual clouds Friday morning, but these will clear out quickly as ridging builds over the region. 850 mb temps drop to around 12C Friday afternoon, which will support cooler highs in the mid to upper 70s. We will see the upper low over Canada then start to dominate the weather over most of the Upper Midwest and Great Lakes. It will bring a long wave trough down out of Canada late Saturday. This will bring a sfc front into the forecast area Saturday evening. The front is formidable itself, but then we will have a fairly strong short wave ride along it, and bring another surge of energy to increase the coverage of precipitation Saturday night and Sunday morning. There is plenty of instability of around 1000 J/kg of MU CAPE ahead of the front to support thunder. Shear is healthy too with the upper jet near by, which helps support the marginal risk in place. - Cooler and unsettled next week Obviously the focus has been largely on the near term due to the severe potential, so not much to say about the longer term period. It can be categorized by long wave troughing/lower heights dominating the region. This will result in much cooler temperatures next week compared to this week. In addition, we will have short waves moving through on the periphery of the upper trough. These will bring periodic shower/storm chances to the area off and on next week. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 213 AM EDT Fri Jun 12 2026 A cold front is located north/south through Southwest Lower Michigan at 06z stretching from near HTL to AZO. Lower ceilings to IFR in spots are located near the front. These lower ceiling should clear to the east fairly rapidly in the next 2-4 hours. VFR weather is expected to prevail from roughly 10z through the rest of the TAF period. Winds will shift to the west at all TAF sites early this morning with gusts to 20-25 knots at times through the course of the daylight hours of Friday. && .MARINE... Issued at 304 PM EDT Thu Jun 11 2026 We will leave the Small Craft Advisory and Beach Hazards Statement as is for tonight and Friday. We saw winds and waves approaching criteria earlier, but are now in a relative lull before the winds increase again with the approach of the front this evening. Then winds will shift to be from the WNW with cooler air coming in which will build the waves again through the first part of Friday before diminishing. Aside from the synoptic winds, thunderstorm winds could gust much higher which would be accounted for with Special Marine Warnings. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until noon EDT today for MIZ037-043-050- 056-064-071. MARINE...Small Craft Advisory until noon EDT today for LMZ844>849. && $$ DISCUSSION...NJJ AVIATION...Duke MARINE...NJJ

NWS GRR Office Area Forecast Discussion