188 FXUS63 KGRR 162343 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 743 PM EDT Sun Oct 16 2022 LATEST UPDATE... Aviation .DISCUSSION...(This evening through next Sunday) Issued at 339 PM EDT Sun Oct 16 2022 -- High Winds the next couple of days -- A deepening low will move through the Great Lakes tonight into Monday. Monday evening a 997mb low near Lake Huron will combine with a 1035mb high in the Northern Plains and Canada to place a near 40mb gradient across our region. Winds will steadily ramp up tonight and become gusty in all areas on Monday. There is the potential for some wind advisory gusts along the lakeshore on Monday. A much better threat exists Monday night into Tuesday. After coordinating with offices to the north and south it was decided to hold on on wind headlines at this time. An advisory looks likely in the lakeshore counties Monday night and Tuesday though. Gusts in at least the western half of those counties should see 45-55 mph gusts. Isolated power outages are likely given the magnitude and duration of the wind, especially when combined with leaves still on the trees up and down the lakeshore. Wording about the wind and isolated power outages was put into the HWO, social media posts as well as a message to key partners. -- Snow chances increase Monday into Tuesday -- Wet bulb zero heights slowly fall so that in all areas by Monday night we will be cold enough for snow, meaning wet bulb zero heights drop below 1,500 feet. Tonight the precip type will mainly be in the form of rain. During the day on Monday, there will be some snow mixing in, especially up along U.S. 10 in Central Lower Michigan. Temperatures both today and tonight though and for that matter through the event will be very marginal for any impacts from snow, holding in the 30s and 40s. The best chance for accumulating snow of an inch or greater (which really only occurs in a couple spots in our entire forecast area) comes Monday night into Tuesday. Monday night we will see a Lake Superior connection as multiple snow bands in a NNW flow push into the U.S 10 corridor especially between Scottville and Clare. The higher ground in Lake and Osceola County have the best chance at seeing the ground turn white up there with a slushy accumulation of an inch or two. A dominant NNW flow snow band will work down the length of the lake and push inland across Allegan, Van Buren and Berrien Counties. The lake boundary layer is quite warm this time of year with the nearshore buoys near 60F water temps. The mid lake buoy is down to 55. So, we will not see snow accums near the lakeshore it will occur inland. These areas south and west of GRR will be the other spot in the forecast area that may see some accumulations of an inch or two of wet snow. Can't rule out a few higher amounts in the dominant band sets up and does not move much. Hi Res models show the band shifting around quite a bit though. The remainder of the CWA may see a brief whitening of the ground for a bit after a heavier snow shower rolls through but not expecting much at all given marginal air temps and ground temps that are still in the upper 40s F. Final note with this event is that we may see a few thunderstorms off the lakes as lake induced CAPE values via the NAM rise to in excess of 1,000 J/KG. That is a pretty sizable amount of CAPE for October, but reasonable given delta t's around 20 C. -- Rest of the forecast period through next weekend -- We dry out finally on Wednesday it appears as the lake effect winds down. Much of the rest of the forecast period looks dry so the most impactful weather in this forecast is front loaded for sure. The upper flow goes zonal and then southwest late in the week and into the weekend. For those wanting some warmer weather back the southwest flow pushes highs back into the 60s next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 730 PM EDT Sun Oct 16 2022 Variable conditions are expected for the next 24 hours with lake effect rain showers moving through the region, with highest impacts at MKG, GRR, and AZO. Visibilities have typically been dropping to 3sm-4sm with the passing showers though some 2sm visibilities are possible. Lake-induced thunderstorms may develop in the 06z-12z Monday time frame but especially after 12z Monday. Decided to keep VCTS mention out at this time but we may need to throw that in eventually for MKG and GRR, perhaps AZO. We'll be flirting with IFR at times especially for those three sites, either due to visibility reduction (in the heavier showers and certainly any TSRA) and/or cig reduction, per the latest high- resolution model blend. Combine this with strengthening synoptic- scale wind gusts (initially westerly, then northwesterly) and there will be a variety of aviation hazards not only for this TAF period but lasting into Tuesday as well. && .MARINE... Issued at 339 PM EDT Sun Oct 16 2022 We will be maintaining the current headlines of Small Craft Advisory through 500am in the morning and then a Gale Warning thereafter for Monday, Monday night and Tuesday. This looks to be a high end gale. 45 knot gales are expected. We have some concern that this could overperform with Storm Force winds occurring. There is some storm force wind in the mixed layer at lakeshore and over water points in the NAMnest BUFKIT overviews. If confidence in this increases we may need to upgrade to storm. For right now, the high end gales look good. Waves will steadily ramp up this afternoon and tonight, peaking Monday night most likely, although Tuesday will be a close second in high waves. Wave modeling is showing 15 footers in most zones Monday night into Tuesday. Some of the highest waves should be see down towards South Haven and St. Joe with some 18 footers showing up. We are not overly concerned in our area for lakeshore flooding with this system given the lake is down 2-3 feet from the highs of a couple of years ago. Based on Holland MI water levels this afternoon it will take a rise of 3.1 feet to get us up into the Advisory levels of 582.5 to 582.75 feet. We do not see a rise of that magnitude occurring. So, we are not expecting waves to be attacking the base of the fore dune up and down the shoreline. Large waves will be rolling up on the beach, just not well into the dune line like a couple years ago. Our biggest concern on the lake, outside of very hazardous conditions for all mariners is the threat to life in and near piers. Piers will be extremely dangerous the next several days and should be avoided at all cost. We expect both piers (south and north) at all harbors to be swamped by large rolling waves. Best option is to stay safe and observe the waves from the numerous webcams online. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 5 AM EDT Monday for LMZ844>849. Gale Warning from 5 AM Monday to 8 PM EDT Tuesday for LMZ844>849. && $$ DISCUSSION...Duke AVIATION...Hoving MARINE...Duke