505 FXUS63 KGRR 130836 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 336 AM EST Sat Dec 13 2025 .KEY MESSAGES... - Lake effect snow and cold tonight into Sunday - Turning warmer this week with rain in the forecast Thursday && .DISCUSSION... Issued at 336 AM EST Sat Dec 13 2025 - Lake effect snow and cold tonight into Sunday Main forecast focus this morning was on the Arctic air intrusion combined with lake effect snow. Specifically the concern is the threat of impacted travel. We have issued a Winter Weather Advisory from this afternoon through tonight and into Sunday morning. The advisory is not for heavy snow, but instead impacted travel. We will see 1 to 3 inches of snow in the lakeshore counties during the aforementioned time frame with an isolated 4 inch amount not out of the question. The issue however is the fact that temperatures will continue to plummet throughout the day. A strong mid level shortwave will work through the region tonight which will give a boost to the lake effect snow. Again, heavy snow is not expected but the combination of very cold air, small/fine snowflakes and blustery conditions/blowing-drifting snow (NW 15-25 mph) will create impacted travel. When 850mb air of -20C or colder works into the area it correlates to surface temperatures below 15F. At these temperatures salt becomes less effective. Any light snow production, whether it is heavy or not is pasted into a glaze of ice many times due to a constant refreezing process. Therefore, the main concern is impacted travel from this afternoon through Sunday morning for slick conditions. People will need to slow down and allow extra travel time. We do not see these conditions (very cold temperatures and snowfall) all of the time and folks can be unprepared. The HRRR shows temperatures dipping to +5F tonight in portions of the Winter Weather Advisory. Again, those surface temperatures with a consistent light snow is the concern with regard to travel. As for some of the meteorological parameters agree with previous discussions that the depth of moisture is shallow, but it does increase this evening and tonight with a healthy mid level shortwave working through. At the lakeshore BUFKIT points, the DGZ is off the deck so there should be consistent light snow production. Lift is fairly strong within the shallow cloud layer. The heaviest snow will certainly be tonight. Delta T`s will reach the mid 20s C which is extreme. - Turning warmer this week with rain in the forecast Thursday The remainder of the forecast shows the upper pattern becoming more zonal with a system forecast to move through the Great Lakes region on Thursday. Southerly flow ahead of this system will push us back into the 30s and even some 40s mid week. At this point, the precipitation looks to be mainly rain with amounts that do not look too significant on the order of a half inch. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1125 PM EST Fri Dec 12 2025 Radar shows light snow developing over central Lower ahead of the arctic cold front that`s moving across central Wisconsin. We`ll see visibilities fall to 1.5sm - 4sm in light snow as this initial burst of snow moves through. Accumulations around an inch are possible, especially along the I-96 terminals. Once the arctic air moves overhead, extreme instability over the lake will develop and produce lake effect snow. However, the dendritic growth zone will plunge to near the surface resulting in a dgz that`s only 2-4k ft thick. In addition, moisture isn`t all the plentiful either. Flake size will likely be pretty small in the lake effect but visibilities are likely to fall to IFR at times along/west of US-131. While accumulations won`t be significant, the lower vsbys will likely impact aircraft operations to some degree. GRR Airport DSS Update No changes to the airport briefing information provided from the day shift. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory from 4 PM this afternoon to 11 AM EST Sunday for MIZ037-038-043-050-056-064-071-072. MARINE...Small Craft Advisory until 7 PM EST Sunday for LMZ844>849. && $$ DISCUSSION...Duke AVIATION...04

NWS GRR Office Area Forecast Discussion


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