467 FXUS63 KGRR 151204 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 704 AM EST Mon Dec 15 2025 .KEY MESSAGES... - A little bit of light snow possible across Central Lower today - Quiet weather with slow warming into mid week - Rain to move through on Thursday - Colder with lake effect snow on Friday && .DISCUSSION... Issued at 356 AM EST Mon Dec 15 2025 - A little bit of light snow possible across Central Lower today Northwest upper flow persists today on the backside of a departing trough across the Great Lakes region. A shortwave diving southeast through the Northern Great Lakes will brush by Central Lower Michigan. A period of light snow is possible this morning, especially up towards U.S. 10 as a zone of isentropic lift moves through. While lift looks fairly strong, condensation pressure deficits are still fairly high leading to a lower confidence in much occurring up there. BUFKIT overviews bear this out as well, with a break in the moisture between mid level isentropic lift moisture and the low clouds still in place. Best chance for any accumulation would be towards Clare and Harrison one the order of a dusting to a half inch if we see that. - Quiet weather with slow warming into mid week A period of dry weather looks to occur from late this afternoon through Wednesday night. A cold front does move through the area Tuesday night into Wednesday morning, but it looks to move through dry. The main weather item of note in this period is a gradual warming of temperatures. 850mb temperatures rise from around -10C this morning overhead to +7C Tuesday night and again Wednesday night. We will be in the 30s for highs both Tuesday and Wednesday so we should see the snowpack ripen up a bit and we will begin to melt some snow and ice off of secondary/neighborhood roads. - Rain to move through on Thursday The biggest surge in warmth and moisture will come on Thursday ahead of a frontal passage. The surface front is associated with and being driven by an amplifying wave that moves out of the Rockies and into the Plains Wednesday night taking aim on the Great Lakes for Thursday. As the surface low deepens into the 980s mb on Thursday the southerly inflow into our area increases. So much so that the 850mb LLJ ramps up to 55-60 knots in the GFS, ECMWF and Canadian models. Southwest wind gusts in the stronger ECWMF increase to 40-50mph on Thursday. The southerly surge will also bring moisture with PWAT values increasing to around 0.90 inches which is above the 90th percentile in sounding climatology for DTX and near the daily max for the day. Surface dew points will climb into the 40s. Thankfully, rainfall amounts do not look to be excessive (towards a half inch in most areas) and the warmer air will not be in the area that long as its quickly swept to the east by the cold front in the afternoon. As we talked about yesterday, not expecting big impacts from the rain and brief warm up. The snowpack will ripen, we will lose some depth and there will be some ponding of water in areas where storm drains are packed by ice and snow. Widespread flooding issues are not anticipated and that is backed up by our Hydrologic Ensemble Forecast simulations. The sites that could see a quick run to near bankfull would be our more quick response sites like Sycamore Creek at Holt, the Portage River at Vicksburg and the Grand at Jackson. - Colder with lake effect snow on Friday A quick burst of lake effect snow is expected Thursday night into Friday morning, but the moisture availability will be short lived and any lake effect likely gets shut down by Friday afternoon. A quick 1-3 or 2-4 inches looks like the best bet at this point, but we have time to zero in on this snow chance as it gets closer. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 703 AM EST Mon Dec 15 2025 The two main aviation concerns today are MVFR ceilings and the wind. With regard to ceilings, there will be enough instability over Lake Michigan for the production of lake stratocumulus both today and tonight. The clouds will likely vary between 1500 and 2500 feet and be dictated by wind direction. So, as the winds have backed to the southwest overnight from the west the lower ceilings have moved northward with the mean wind direction. LAN for instance has cleared out the low clouds. MKG in fact is the only site still indicating a MVFR ceiling at 1800 feet. The winds will veer to the west once again this afternoon and evening and the MVFR ceilings will expand once again through all of the TAF sites. The TAF sites should largely stay precipitation free the next 24 hours. As for the wind it will get gusty this morning fairly quick with all sites developing gusts between 20-30 knots by midday or 16Z or so. Winds will subside to back below 10 knots once again by 00Z this evening. && .MARINE... Issued at 356 AM EST Mon Dec 15 2025 We are still looking good for a borderline / short duration gale event this morning. Mixing depth looks to tap into 34-38 knots between 7am and 1pm. That is the time frame where we should see occasional gale gusts at our lakeshore marine ob sites like Big Sable Point, Muskegon GLERL, Holland NOS and South Haven GLERL. Winds ramp down fairly quick in the early to mid afternoon which is when we will be able to downgrade into a Small Craft Advisory. Another short duration gale event looks possible Tuesday evening. These gale event are due to surface low pressure systems zipping east across Canada in zonal flow. As each system slides by to our north the pressure gradient tightens for a time when combined with surface high pressure to our south. Waves will push to around 10-12 feet in both events in southwest flow. Holland to the north will be where the largest waves will be found. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Gale Warning until 3 PM EST this afternoon for LMZ844>849. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion