FXUS63 KGRR 082301 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 601 PM EST Sun Dec 8 2024 .KEY MESSAGES... - Light Rain/Drizzle Tonight into Monday - Colder with Lake Effect Snow Tuesday through Thursday && .DISCUSSION... Issued at 227 PM EST Sun Dec 8 2024 - Light Rain/Drizzle Tonight into Monday The upper level low over Oklahoma will ride the subtropical jet northeast into the area late tonight through Monday morning. With the southwest flow and advancement of this system temperatures overnight won't drop much with the warm air advection and rising dew points as we tap into moisture from the gulf. The current conditions over Oklahoma and Arkansas will be similar to what we see overnight through Monday morning with low clouds, drizzle, and light rain. The 850 mb front moves through during the late morning and early afternoon with drier air filtering in behind it, thus ending any rain or drizzle. The potential for any freezing drizzle remains very low due to temperatures likely remaining above freezing and surfaces warming over the past couple of days. - Colder with Lake Effect Snow Tuesday through Thursday Temperatures fall behind Monday's front with 850 temperatures falling to around minus 10C by Tuesday evening. With positive vorticity advection within the southwest ahead of an advancing upper level trough, we could see some snow showers develop along the lakeshore during the day Tuesday and then pick up Tuesday night into Wednesday as the trough axis moves through and temperatures continue to fall. The upper level low is expected to linger over the northern Great Lakes into Thursday with 850mb temperatures bottoming out around minus 20C (ensemble mean). Even with variable outcomes on how deep the trough will be over the area, there is increasing confidence that we will see these colder temperatures aloft. Lake Michigan temperatures are currently around 8C, with the current forecast this would result in temperature differences around 25C to 30C. This will ramp up the lake effect snow production Wednesday night into Thursday with low level moisture likely in the dendritic growth zone due to the cold temperatures (highs around 15 degrees Thursday which would be minus 9C). With this set up expect accumulating snow and gusty winds to make a return along the lakeshore causing impacts at least for the Wednesday morning through Thursday morning commutes. Areas farther inland could see impacts as well depending on where the lake effect bands set up. With the mentioned cold and winds above, wind chills will be around 0 Wednesday night into Thursday. Temperatures then gradually warm more toward normal values (highs in the 30s, lows in the 20s this weekend. Additional chances for rain and snow exist over the weekend, but overall variances in the pattern make it hard to pinpoint any finer details. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 600 PM EST Sun Dec 8 2024 VFR conditions this evening will gradually deteriorate to a mix of MVFR and IFR during the early morning hours Monday as low cigs and light rain showers and drizzle along with patchy fog develops. The MVFR/IFR conditions will linger Monday morning before gradually improving to VFR in the afternoon as patchy fog dissipates and low clouds and lingering rain showers move out. && .MARINE... Issued at 227 PM EST Sun Dec 8 2024 Small Craft Advisory conditions are possible Monday night into Tuesday due to southwest to west winds to 25 knots and waves 3 to 5 feet. Waves and winds increase Wednesday into Thursday with a frontal passage with stronger northwest winds behind it. There could be a period of gales before waves and winds subside Thursday night. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...RAH AVIATION...Laurens MARINE...RAH