488 FXUS63 KGRR 210812 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 312 AM EST Wed Jan 21 2026 .KEY MESSAGES... - Moderate to Heavy Snow This Morning - Moderate Snow Again Tonight Then Lighter Snow into the Weekend - Cold Air Arrives Thursday Night, Dangerous Cold This Weekend && .DISCUSSION... Issued at 312 AM EST Wed Jan 21 2026 - Moderate to Heavy Snow This Morning Currently, we an upper PV maximum crossing the Midwest, with satellite indicating a classic baroclinic leaf signature over the Missouri/Iowa border. Surface response to this feature is evident with a pressure minimum over southeast IA and pressure falls maximized across northern IL. A band of snow associated with FGEN and isentropic ascent north of a warm front is noted east- northeast of the surface low along the WI/IL border. Closer to home, we have seen an initial burst of snow impacting the winter storm warned area of Ottawa, Muskegon, and Oceana Counties. Numerous observation sites show backing winds just onshore, indicating a response to strong frontogenesis underway along the lake/land air density gradient. Radar returns are blossoming over southern Lake MI with the approach of the previously mentioned FGEN band, so expect moderate to heavy snowfall intensities to persist into and beyond the morning commute. Largest hourly rates could actually occur in the 8 to 9 AM timeframe for some areas as the wind convergence axis associated with the FGEN region pivots in an onshore orientation. Snow amounts generally look on track. However, would not be surprised to see southern Mason County get 8 inches. This is not high confidence however and will keep the advisory going there instead of upgrading to a warning. As noted previously, the entire region can expect continuing, albeit lighter, snow lasting into the afternoon and evening. - Moderate Snow Again Tonight Then Lighter Snow into the Weekend Another Clipper-like PV max that currently is dropping into the Northern Plains will provide another round of lake enhanced snowfall. Thus, Thursday will offer yet another challenging commute. As noted previously, we will continue to see episodic lake enhanced snow into the weekend, but amounts should be more anemic given the arrival of bitterly cold air that will yield exceptionally poor microphysics for snow production. - Cold Air Arrives Thursday Night, Dangerous Cold This Weekend Temperatures will plummet Thursday night, likely dropping below zero by 7 AM Friday over central interior Lower MI. The GEFS and EC Ensemble indicate a greater than 90 percent chance of apparent temperatures already colder than -15F by 7 AM Friday from I-96 northward, so cold weather preparations will need to be in place early. Friday night looks even more impressive. The EC ensemble, which has been very consistent in advertising bitterly cold temperatures during this time, gives a greater than 70 percent chance of apparent temperatures -25F or colder over interior Lower Michigan Saturday morning. Extreme southwest Lower may be spared the bitterest cold due to lake-modified air. Even on Sunday morning, interior Lower MI is looking at greater than a 50 percent chance of -15F apparent temperatures. All of this is to say that dangerous cold can be expected over much of this weekend. Although temperatures will moderate some next week, they will remain below normal. There is a signal for a Gulf low lifting towards the OH Valley in the Sunday/Monday timeframe ahead of an approaching phased upper trough, but it`s way too early to nail down specifics about its track and where precipitation will occur. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1156 PM EST Tue Jan 20 2026 We will be seeing snow develop across all of the terminals over the next 3 hours from West to East. KMKG already is seeing enhanced snow with lake enhancement occuring. This is bringing them down into IFR and LIFR. All of the other sites will start as MVFR and drop down into IFR after a couple of hours of snow falling. The worst of the conditions will be roughly from about 08/09z until about 14-16z. KMKG could get down to VLIFR in the heavier bands. We will see a break in the action after the snow moves out by 18z Wednesday. MVFR conditions will likely persist with low clouds. This break will be short lived as another area of snow will move in to KMKG around 00z Thu and by 02/03z elsewhere. More IFR and LIFR conditions expected. For the GRR 06z update... No changes to the forecast at this time. The snow looks to start here around 07-08z. We are generally expecting 2-3 inches of a normal consistency type of snow. The heaviest snow will occur from 09/10z until about 15z, then tapering off after that. && .MARINE... Issued at 312 AM EST Wed Jan 21 2026 No changes planned to the current forecast. We will be easing into gale conditions for much of the area this afternoon. Heavy freezing spray will also be a concern, especially Thursday night into Friday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 10 AM EST this morning for MIZ037- 038-044>046-051-052-057>059-064>067-071>074. Winter Storm Warning until 10 AM EST this morning for MIZ043-050- 056. MARINE...Small Craft Advisory until 4 PM EST this afternoon for LMZ844>849. Gale Warning from 4 PM this afternoon to 7 AM EST Friday for LMZ844>848. Heavy Freezing Spray Warning from 10 PM this evening to 4 AM EST Saturday for LMZ844>849. && $$ DISCUSSION...TJT AVIATION...NJJ MARINE...TJT

NWS GRR Office Area Forecast Discussion