300 FXUS63 KGRR 291455 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1055 AM EDT Fri Sep 29 2023 LATEST UPDATE... Update .UPDATE... Issued at 1041 AM EDT Fri Sep 29 2023 No changes to the going forecast with the morning update. Widespread stratus remains in place across lower Michigan this morning with mostly cloudy to cloudy skies at all of our observation sites. Short range guidance including the HREF continues to support plenty of cloud cover remaining in place for much of the day. A few breaks in the clouds are possible mid to late this afternoon as cloud bases lift before more widespread clearing occurs this evening. Highs today will be in the low to mid seventies, coolest east of US131 where the abundant cloud cover holds on the longest. && .SHORT TERM...(Today through Saturday) Issued at 224 AM EDT Fri Sep 29 2023 - Patchy dense fog early this morning Good radiational cooling occurred overnight generally north of Muskegon as the skies remained clear for much of the night. Surface temperatures fell into the upper 40s to lower 50s and that resulted in locally dense fog. Ludington reported a visibility of 1/4 mile in the past hour. Satellite imagery shows the fog across portions of Mason and Oceana counties. However the fog may decrease going into daybreak as a large stratus deck was headed into those locations. Based on this forecast trend, we will not go with any dense fog headlines at this time. - Gradual warmup through Saturday A low level thermal trough will be in place today. This, combined with limited sunshine will likely lead to max temperatures struggling to go much higher than the lower 70s. That changes on Saturday as the area will see a greater amount of sunshine and the low level thermal trough starts to shift slowly east. It's looking likely that we will see many locations reaching into the mid to upper 70s. Ensemble temperature forecasts from the various models support this scenario as well. .LONG TERM...(Saturday night through Thursday) Issued at 224 AM EDT Fri Sep 29 2023 - Still on track for a significant warmup into the middle of next week Ensemble temperature forecasts show very little spread within each model Sunday into Wednesday. They do feature some differences compared to one another with the GFS still being the warmest. Blending the forecasts yields high temperatures in the upper 70's to near 80 on Sunday and low 80's for Monday through Tuesday. Even Wednesday has the potential to make a run at 80 degrees, but an approaching mid to upper level wave may limit that potential. The incoming 00z ECMWF shows the 925 mb thermal ridge over the area on Wednesday. Mixing to that level would support max T's reaching 80. Based on this we will bump up temps for Wednesday a degree or two. - Mainly dry into the middle of next week Subsidence, warmth aloft and limited moisture will act to limit the potential for rain showers through Wednesday. After that, the forecast is not as certain. A mid to upper level wave tracks through the Great Lakes Region Thursday into Friday. The models have not shown good continuity from run to run on this wave. Currently the latest GFS has it as a positively tilted feature at 500 mb. The Canadian keeps the bulk of the energy up in Canada, while the ECMWF is stronger with the wave and would support a greater potential for showers. We will feature increasing POPs for the area Wednesday night into Thursday, but still keep them relatively low given the model spread. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 712 AM EDT Fri Sep 29 2023 Low clouds and fog will persist this morning leading to areas of IFR impacts. As the day progresses the cloud bases will likely rise into the VFR category during the afternoon. With some potential for clearing later this afternoon into the evening, good radiational cooling for the start of the night may lead to fog and low clouds reforming. The pressure gradient remains relatively weak so wind values will mostly remain under 10 knots. && .MARINE... Issued at 1257 AM EDT Fri Sep 29 2023 The pressure gradient remains relatively weak Friday and Saturday as high pressure in northern New England retrogrades westward into Michigan. That will support the winds largely remaining under 15 knots. On Sunday a southerly flow will set up and start to strengthen, however even that will be a slow increase and we may not see gusts reaching 20 knots until later Monday or perhaps Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...Thomas SHORT TERM...MJS LONG TERM...MJS AVIATION...MJS MARINE...MJS