989 FXUS63 KGRR 291843 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 243 PM EDT Wed Apr 29 2026 .KEY MESSAGES... - Precipitation ending late tonight, then possible frost/freeze - Afternoon showers Thursday and Friday, frost/freeze potential - Unsettled early next week with greater rain chances && .DISCUSSION... Issued at 243 PM EDT Wed Apr 29 2026 - Precipitation ending late tonight, then possible frost/freeze An extensive area of precipitation was crossing southwest Lower MI early this afternoon and is expected to dissipate/exit by late tonight. There is a well defined upper PV max driving this precipitation. Additional precipitation is noted over WI with separate and somewhat weaker upper PV support. However, CAM guidance suggests this is chiefly forced by diurnal destabilization and it will likely not make it into Lower MI. After discussion with APX, decided to go with a freeze warning for interior northern counties and a frost advisory extending south towards I-96 overnight. There is a lot of bust potential with this forecast because there are questions about how quickly we will lose cloudiness overnight. Also, we will now be dealing with a bit more soil moisture than before, meaning slightly more resilience against falling air temperatures. - Afternoon showers Thursday and Friday, frost/freeze potential With a seasonably deep upper low over the western Great Lakes and cold temperatures aloft, there remains the chance for at least some afternoon showers, mainly over interior Lower MI, thanks to diurnal surface insolation yielding favorable lapse rates for moderately deep moist convection. Thunder is not expected per SPC outlooks and instability progs. Temperatures in the lower troposphere look to be colder Friday and Saturday mornings. Additionally, there is greater potential for clouds clearing at night. Hence, we expect a growing threat for nighttime frost/freeze conditions as we go into the latter part of the week and into the weekend. - Unsettled early next week with greater rain chances Guidance is coming into better agreement regarding a strong upper PV max pivoting into the western Great Lakes on the periphery of a broader upper low. This looks favorable chiefly for rain showers given the arrival of best upper forcing in the morning hours when conditional instability tends to be at its minimum. As noted previously, we will see increasingly Gulf-sourced lower tropospheric moisture as we move into the middle of next week. This will allow conditional instability to develop and increase the chances for thunderstorms. By late in the week, deep southwesterly flow looks like it could set up somewhere over the eastern U.S. and this will definitely need to be watched since both convective and hydrologic hazards could be in play wherever this occurs. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 142 PM EDT Wed Apr 29 2026 Light rain associated with an upper trough moving through the region will continue to fall this afternoon before ending late in the day. IFR cigs are expected overnight due to abundant low level moisture. Some improvement is expected Thursday morning as slightly drier air advects in from the west. && .MARINE... Issued at 243 PM EDT Wed Apr 29 2026 Waves could make a brief run to around 3 feet tonight over our far southern marine zones. However, this is not terribly significant and no concerns are noted at this time. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Freeze Warning from 2 AM to 9 AM EDT Thursday for MIZ038>040-045. Frost Advisory from 2 AM to 9 AM EDT Thursday for MIZ044-046-051- 052-057>059-065-066. MARINE...None. && $$ DISCUSSION...TJT AVIATION...04 MARINE...TJT

NWS GRR Office Area Forecast Discussion


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