627 FXUS63 KGRR 161102 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 702 AM EDT Thu May 16 2024 .KEY MESSAGES... - Showers and storms late today and tonight - Dry and very mild weekend - Chance of showers/storms Monday through Tuesday night && .DISCUSSION... Issued at 327 AM EDT Thu May 16 2024 - Showers and storms late today and tonight Mild weather is forecast today with partial sunshine and as winds become south to southwesterly out ahead of the system approaching from the west. High temps will reach the low to mid 70s (except cooler near the Lake MI shoreline). Clouds will gradually increase through the day but most of the day will be dry. Some showers and thunderstorms will begin to develop by late this afternoon as MUCape values reach 500-750 j/kg over our sw fcst area by then. A consensus of 00Z HREF svr wx parameters suggests that marginally severe convection late this aftn/eve will stay to our west across southern WI. That is where there is potential for stronger instability to develop along with favorable 0-6km shear on the order of 30-40 kts and forcing from the front. We expect weakening convection to gradually move in ahead of the low pressure system and upper disturbance this evening due to relatively weak instability over our area. A few showers and storms will linger Friday with a weak frontal boundary still in our area. - Dry and very mild weekend Upper riding will build into the Great Lakes this weekend and temperatures will respond by climbing well above normal. Highs are going to be in the 80s Saturday and Sunday along with quite a bit of sunshine. - Chance of showers/storms Monday through Tuesday night We're still keeping an eye on a potential stormy pattern Monday afternoon through Tuesday night. The models are quite a bit more frisky in regard to generating instability through that period than last night's runs. A northern stream low will push a cold front toward the region Monday and bring in a strong stream of moisture with it. A minor short wave looks to accompany the front as it moves toward Lake MI Monday afternoon. MUCAPE rises to 1200 j/kg near the front and showers and storms will probably develop along the boundary and clip at least the western cwa Monday afternoon/night. GFS and Euro show a second wave developing on the front and moving northeastward toward Lower MI Tuesday. A stronger short wave rotating around the low will be a catalyst for convective development Tuesday afternoon to the west that may move across the cwa Tuesday afternoon/evening. The LLJ looks to be stronger as does the instability and especially the shear; we could be looking at strong/severe storms late Tuesday. Temperatures will cool off a bit behind the cold front Wednesday/Thursday. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 658 AM EDT Thu May 16 2024 High clouds will continue to move over the terminals today but cigs will remain VFR until later this evening. A cold front will move across Lower MI later tonight. Deep moisture along the frontal boundary will result in showers and MVFR/IFR cigs and visibilities developing near MKG toward midnight and spreading southeast after midnight. There may be a rumble of thunder too. && .MARINE... Issued at 327 AM EDT Thu May 16 2024 Winds will gradually veer to the south and then to the southwest to west this afternoon. Wind speeds will be fairly light at only around 10-15 kts. Wind speeds will remain fairly minimal through late week and this weekend and there really are no concerns for hazardous winds/waves through then. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Laurens/04 AVIATION...04 MARINE...Laurens