483 FXUS63 KGRR 131856 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 256 PM EDT Wed May 13 2026 .KEY MESSAGES... - Mainly dry conditions into Friday - Chances for showers and storms Sunday - Strong to potentially severe storms on Monday && .DISCUSSION... Issued at 256 PM EDT Wed May 13 2026 - Mainly dry conditions into Friday Mainly dry weather is expected through Friday at this point. High pressure will build in tonight and be located over the region on Thursday. We will see an erosion of the clouds from west to east this afternoon and evening. It may take towards midnight or slightly after until the U.S. 127 corridor scatters the clouds out. The high slides off to the east Thursday night allowing a southerly flow to develop for Friday and Saturday. We cannot cannot rule out some isolated to scattered showers both Friday and Saturday in a warm air advection regime. Models are not kicking out significant QPF however with our forecast showing a few hundredths of precipitation in both Friday and Saturday combined. - Chances for showers and storms Sunday Sunday will start out with ridging extending into the forecast area from the north, an extension of a surface high over Ontario. As we work through the day however a warm front will lift in from the south. This is a healthy surge of moisture with 850mb dew points rising from +8C to +14C. The 850mb LLJ in place pushing this moisture is on the order of 30 knots which is more than sufficient to produce showers and storms. MUCAPE values via the GFS and ECMWF are forecast to push towards 1,000 j/kg. Feeling at this point is severe weather cannot be ruled out, but a better chances exists on Monday. - Strong to potentially severe storms on Monday Better dynamics and stronger wind fields exist on Monday which should boost the threat for severe weather a bit higher as compared to Sunday. 45 knot winds at 850mb and a surge of low level moisture (+14C dew points at 850mb and surface dew points of almost 70F) should give us a chance for severe weather. The mid level shortwave in the 12Z runs looks a bit further west which may trend the threat a little bit to the west as well, but we will be monitoring the forecast as we move forward. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 155 PM EDT Wed May 13 2026 Widespread MVFR ceilings /1.5-2.5 kft/ prevail over West Michigan early this afternoon, thanks to cool/cyclonic northwest flow across the region. As a surface ridge approaches the western Great Lakes this evening expect the cyclonic flow to slowly weaken, and this, coupled with filtered/weak mid May sun should allow ceilings to lift and/or clouds to break up from west to east. TAFs reflect this transition to VFR conditions initially at MKG as early as 22Z... slowly spreading east with VFR conditions finally arriving at LAN/JXN by about 07Z. VFR weather expected Thursday, as mainly clear skies early give way to scattered diurnal CU by 15-16Z. NW breezes gusting to around 25 kt this afternoon will subside this evening, and continue from the NW around 10 kts Thursday. && .MARINE... Issued at 256 PM EDT Wed May 13 2026 We have had some gale gusts as expected today, but we have trended back down a bit more into Small Craft Advisory territory as we move through the mid afternoon hours. Northwest winds of 20 to 30 knots are occurring at 200pm. We expected those type of winds to prevail into the evening hours before winds gradually begin to settle/diminish into the 10 to 20 knot range for tonight. The latest WaveWatch3 run matches expectation well with waves subsiding below 4 feet by 200am. Will therefore let the current SCA stand as is with an expiration of 200am. High pressure builds in for Thursday bringing quiescent conditions. Winds ramp up again for Friday out of the south which will likely push us back into Small Craft Advisory conditions. The weekend weather on the big lake looks fairly benign, but we could be looking at fog developing given higher dew points advecting over cold lake waters. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 2 AM EDT Thursday for LMZ844>849. && $$ DISCUSSION...Duke AVIATION...Smith MARINE...Duke

NWS GRR Office Area Forecast Discussion