830 FXUS63 KGRR 012317 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 717 PM EDT Tue Jul 1 2025 .KEY MESSAGES... - Scattered Showers/Storms Wednesday-Friday - Warm This Weekend With a Chance of Showers and Storms Saturday Night into Sunday && .DISCUSSION... Issued at 158 PM EDT Tue Jul 1 2025 - Scattered Showers/Storms Wednesday-Friday Subsidence from a departing trough overhead has led to plenty of sunshine today with highs in the 80s forecasted. Conditions will remain dry through the night and into Wednesday morning before precipitation chances increase Wednesday afternoon. The forcing for any precipitation will be the combination of a few factors. 1) Lake breeze convergence 2) A weak frontal boundary across northern Michigan and 3) a mid- level wave providing some synoptic assistance. The Storm Prediction Center currently has much of the area in a Marginal risk of severe thunderstorms Wednesday. Cannot rule out an isolated strong to severe thunderstorm, with deep layer shear around 30 knots with MUCAPE around 1000 J/kg. However the marginal thermodynamics has confidence in any severe storms low. If a storm can become strong to severe, steep 0-3km lapse rates have gusty winds as the main concern. Much of the area is likely to stay dry Wednesday with areas near US127 and/or north of M20 having the best potential for scattered storms as supported by HREF guidance. The aforementioned front continues to slowly drift through the region Thursday. This will allow the chance for widely scattered showers and thunderstorms to develop, though once again most will remain dry. Areas east of US131 and near and south of M46 will have the best chance for a shower or storm. A warm front crosses the area Friday marking the beginning of return flow from the Gulf on the west side of a ridge. Warmer conditions are expected with highs in the upper 80s to low 90s. A few showers and storms are possible as this front crosses the area. However mid-level height rises will make it difficult for widespread precipitation to form meaning Independence Day will not be a washout. - Warm This Weekend With a Chance of Showers and Storms Saturday Night into Sunday. Warm southwesterly flow continues to take hold into the weekend as 850mb temps climb to the upper teens Celsius. highs climb into the 90s for Saturday. Sunday is a bit more uncertain as that will depend on the exact timing of a cold frontal passage across the area. Dewpoints near 70 will mean heat indices Friday and Saturday will climb into the 90s. This cold frontal passage Saturday Night into Sunday will bring the potential for more widespread showers and storms into the area aided by a mid-level wave, though this mid-level wave will not provide much in the way of synoptic assistance as it`s shearing out as it arrives. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 716 PM EDT Tue Jul 1 2025 Diurnal cu is dissipating which will leave clear skies overnight. A weak short wave trough will approach Wednesday afternoon and may fire a shower or storm after 18z. This would affect LAN/JXN and perhaps BTL, but chances are only around 20 percent and so were left out of the TAFs. && .MARINE... Issued at 108 PM EDT Tue Jul 1 2025 High pressure will remain overhead for the next few days resulting in waves aob 2 feet. As the high moves east Friday, southwest winds will increase and waves will respond by building to 2 to 4 feet late late Friday into Saturday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Thomas AVIATION...04 MARINE...04

NWS GRR Office Area Forecast Discussion


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