637 FXUS63 KGRR 141133 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 733 AM EDT Sat Jun 14 2025 .KEY MESSAGES... - Dry weekend - Increasing humidity and midweek convection && .DISCUSSION... Issued at 334 AM EDT Sat Jun 14 2025 - Dry weekend Recent radar imagery shows the last of the light rain south of I-96 continues to whither away as low pressure over Indiana moves east. IR loop shows abundant mid clouds across the region due to a combination of the low to the south and minor short waves to the north moving quickly in the quasi zonal flow over the UP. Aloft, zonal flow will overtake much of the western Great Lakes this weekend bringing a mix of clouds and sun. High pressure over Ontario will continue to produce an easterly flow and (for the most part) lower humidity values; dewpoints mainly in the 50s are expected today and Sunday. Highs today will reach the mid 70s and tomorrow the lower 80s. - Increasing humidity and midweek convection The Ontario high will move east Monday which will enable a southwest flow to develop. Higher heat and more humidity will be the result as dewpoints climb into the 60s. Ensembles of both the GFS and ECMWF sows low pressure developing over the Missouri Valley Tuesday and moving northeast toward Wisconsin by early Wednesday. Most of the ECMWF ensemble members produce rainfall; ensemble mean is closing in on an inch. The GFS mean is about half the ECMWF. LREF ensemble probabilities of greater than a half inch of rain Tuesday into Wednesday is just above 50 percent north of I-96 and closer to 75 percent near I-94. Parts of the central cwa are fairly parched, according to the Michigan Drought Monitor and so any rain received would be beneficial. As the low and associated frontal boundary move through the cwa Wednesday, instability ramps up with MUCAPE values above 2k j/kg and moisture transport vector maxima through the heart of the cwa. Shear values in the 40-50kt range would point toward convective organization potential so this will be monitored closely. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 727 AM EDT Sat Jun 14 2025 Early visible satellite imagery shows generally clear skies at MKG. Elsewhere, a mix of IFR/MVFR/VFR ceilings. GRR currently is 2k bkn but clearing skies upstream should render the site VFR by 12z. The I-94 terminals are mostly IFR/MVFR. Look for gradual improvement as the day progresses. && .MARINE... Issued at 334 AM EDT Sat Jun 14 2025 A weak pressure gradient and high pressure to the north will result in an offshore flow today and low wind speeds/wave heights. Fairly tame marine conditions are expected through the weekend. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...04 AVIATION...04 MARINE...04