843 FXUS63 KGRR 050001 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 701 PM EST Sun Jan 4 2026 .KEY MESSAGES... - Round of Snow Tonight with Potential for Freezing Rain - Rain/Freezing Rain Tuesday into Tuesday Night - Warmer with Periods of Rain Thursday into the Weekend && .DISCUSSION... Issued at 229 PM EST Sun Jan 4 2026 - Round of Snow Tonight with Potential for Freezing Rain Satellite water vapor and airmass RGB imagery show an upper PV maximum has ejected eastward into the northern plains with an attendant closed surface low crossing SD at this time. As noted before, this PV feature will cross central/northern Lower MI overnight, with the best timing for mid-tropospheric upward vertical motion in the 03-06Z Monday timeframe. We are still looking at greater than 50 percent chances of one inch per hour snow accumulations around the US-10 corridor east of Baldwin. Desaturation of the DGZ will occur in the wake of the upper PV maximum. Additionally, we see a signal for the surface low to cross the northwest CWA, which will contribute sufficient low level isentropic lift and surface convergence to induce freezing drizzle for a brief period. Given that the best signal for at least a glaze of ice extends south and west of the current advisory area, we have expanded the advisory to encompass our two northern tiers of counties to address travel hazards for the Monday morning commute. Agree with previous thinking about fog/freezing fog being a concern Monday night into Tuesday so have included this in the forecast. - Rain/Freezing Rain Tuesday into Tuesday Night Another PV maximum and associated surface low will cross Lower MI Tuesday with a slightly more southern track compared to the Sunday night (tonight`s) system. The surface low moves east across southern Lower MI and the swath of heaviest precipitation will be just north of the low track in an area of maximized low level isentropic ascent. There could be a quick accumulation of 0.05 to 0.10 inches of ice east of a Reed City to Big Rapids line on Tuesday morning thanks to a very sluggish diurnal climb in temperatures. This scenario would warrant another advisory for this area if forecast trends hold. Eventually, temperatures should warm enough Tuesday afternoon to result in a transition to rain. - Warmer with Periods of Rain Thursday into the Weekend The overall pattern transitions to phased troughing over the western CONUS. This introduces deep southwesterly flow to the western Great Lakes, which tends to be a wet pattern. The mean trough position crosses the intermountain west and reaches the plains early Friday. This will allow lee cyclogenesis to take shape and bring precipitation to the area Friday night. Most recent available guidance indicates most of this will fall as rain, but a transition to snow is likely to occur at some point overnight into Saturday morning. Any impacts during this time would most plausibly be from excessive runoff due to rain; however, even this is a limited threat given that NBM v5.0 guidance indicates just roughly a 30 percent chance of exceeding one inch or rain accumulation during this time. Heavier rain is more probable south of Lower Michigan near a stationary front, and we will have to monitor whether this threat area shifts north with subsequent forecasts. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 658 PM EST Sun Jan 4 2026 MVFR cigs continue to dominate at most TAF sites and will remain persistent through most of the evening. While a chance remains for light FZRA/FZDZ, those chances are dwindling. However there will be some bands moving through slightly later, in the 06Z to 12Z timeframe that could melt and refreeze as FZRA/FZDZ instead of snow. However, chances are low enough that have left them as Prob30. Heaviest snow remains to the north and any snow affecting TAF sites light and while there is a chance that snowfall is strong enough to reduce vsbys to MVFR at times so have PROB30 to cover any potential. The other aviation concern is for LLWS as a jet will move overhead and will affect TAF sites from 08Z to 13Z from West to East. That 40kt Jet should remain between 015KFT to 020KFT. There should improving conditions after 12Z tomorrow though post frontal low clouds will be possible tomorrow afternoon, after 17Z with MVFR cigs tomorrow afternoon into tomorrow evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 10 AM EST Monday for MIZ037>040- 043>046. MARINE...Small Craft Advisory from 10 PM this evening to 3 PM EST Monday for LMZ844>849. && $$ DISCUSSION...TJT AVIATION...Ceru

NWS GRR Office Area Forecast Discussion