372 FXUS63 KGRR 102258 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 658 PM EDT Mon Aug 10 2026 .KEY MESSAGES... - Unsettled With Several Chances of Showers and Thunderstorms Through Thursday - More Widespread Rainfall Potential This Weekend && .DISCUSSION... Issued at 144 PM EDT Mon Aug 10 2026 - Unsettled With Several Chances of Showers and Thunderstorms Through Thursday Persistent west-northwest flow with several embedded shortwaves will keep a frontal boundary stalled south of the area over the next several days. Each shortwave will drive the potential for showers and thunderstorms until late Thursday into Friday a pattern shift forces the front south. First chance is this afternoon where the NAMNEST, which is best handling ongoing convection, suggests an isolated pop-up thunderstorm or two. Coverage given little mesoscale forcing will be widely isolated with many if not all staying dry. Next chance arrives tonight with the low-level jet just south of the area. This focuses the best convective potential south of the area, though a few showers and storms are possible closer to the front along and south of the I-94 corridor. Attention then turns to Tuesday afternoon where a complex of storms is forecast to either just miss us to the south, or impact our southwest forecast area. Best chance if it does reach us is south of a Grand Haven to Lansing line. With ample deep layer shear (40+ kts) and MUCAPE values north of 2000 J/kg, this complex may have the potential for damaging winds if it impacts our forecast area. This matches the signal seen in several different machine learning guidance tools. However, storm track depends highly on how storms evolve tonight so confidence in any severe weather threat is low. Wednesday and Thursday will feature additional afternoon/evening thunderstorm chances as weak shortwaves interact with the front south of the area. Best chance will be south of I-96, particularly near I-94. The front then is driven south Friday ending the unsettled pattern briefly. There also may be locally heavy rain with any of these rounds, with isolated maximum totals aoa 2 inches shown in HREF/REFS LPMM guidance. - More Widespread Rainfall Potential This Weekend Friday looks to be dry as surface and upper-level ridging suppresses convective potential. However, that pattern changes by Saturday. This weekend, potentially as early as Friday Night, a mid-level wave ejects into the Central Great Lakes driving a surface low across the area. This will bring more widespread precipitation until the low exits late weekend with cooler temperatures with it. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 144 PM EDT Mon Aug 10 2026 Daytime heating, coupled with a moist boundary layer aided by overnight rainfall, has resulted in a SC cloud deck with MVFR ceilings /around 2kft/ at all TAF sites. With continued warming this afternoon, expect SC to lift to VFR CU deck /around 3.5 kft/ after 19-20Z. Stationary front over the Lower Great Lakes will continue to serve as focal for scattered storms next 24 hr, with the next round of thunderstorms potentially moving into SW Lower /including the AZO-BTL TAF sites/ after 02-03Z this evening. Yet another round of storms may be approaching AZO/BTL/GRR after 16Z Tuesday, but will not include in TAFs at this time. Otherwise, expect SCT-BKN mid clouds tonight north of the boundary, along with 2-4SM vsbys in fog after 06-07Z. Winds will remain light throughout TAF period, with westerly flow becoming variable tonight. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 658 PM EDT Mon Aug 10 2026 MVFR cigs have mostly scattered out with mainly mid and high clouds. For the most part, that will persist through the evening. The main caveat is late this evening through around 07z, scattered thunderstorms may develop along a front that may impact AZO/BTL. Then, mostly clear skies and light winds atop a moist boundary layer will allow 2-4SM fog to develop overnight, and potentially some low stratus as well. Can`t rule out (10% chance) of sub 2SM visbys. Fog will dissipate mid to late Tuesday morning. Then, a line of thunderstorms is forecast to track through the region from the west. Confidence is low in where it tracks, with a very real chance it tracks south of the terminals. Have gone PROB30 TSRA for AZO/BTL/JXN where confidence is higher in thunder potential and showers for the other sites where confidence is lower. 17-13z is the main window of concern, and timing and confidence will be refined as upstream trends become clear. && .MARINE... Issued at 144 PM EDT Mon Aug 10 2026 Conditions look to remain below Small Craft Advisory/Beach Hazards Statement levels much of the week given weak gradient flow across the area. The one caveat is that one or more rounds of thunderstorms are likely between tonight and Thursday across the waters. Locally higher winds and waves are possible in any thunderstorms or as a result of their outflow winds even if they miss our part of the lake. Marine headlines may be needed Friday Night into the weekend as a more robust system crosses the Central Great Lakes. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Thomas AVIATION...Thomas MARINE...Thomas

NWS GRR Office Area Forecast Discussion