FXUS63 KIWX 040537 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 1237 AM EST Wed Dec 4 2024 .KEY MESSAGES... - Lake effect snow, gusty winds, and lowered visibility are expected Wednesday evening overnight into early Thursday. A winter storm watch has been issued for Berrien, Cass, and St Joseph, MI with lowered visibility possible in the snow, especially closer to Lake MI. Winds could gust between 30 and 40 mph with 45 mph possible near Lake MI. Lake effect snow continues, but slowly wanes through the day Thursday. Hazardous travel is possible in these areas. - The cold air is expected to last through Friday with highs Thursday and Friday in the mid 20s to around 30 degrees. Lows are expected to be in the teens to around 20 degrees. Apparent temperatures drop below zero south of US-30 Wednesday night. - Our next chance for precipitation is expected to occur Sunday night/Monday. && .DISCUSSION... Issued at 253 PM EST Tue Dec 3 2024 Low level southwesterly trajectories continue to take the remaining lake effect snow clouds east away from the area as surface high pressure pushes into the Tennessee River Valley. Those trajectories do look to bring in warmer air near the low levels and this is expected to keep the area warmer than it was last night with low to mid 20s as opposed to areas seeing teens creep into areas south of US-30. This should also allow temperatures to creep back into the 30s and above freezing on Wednesday. Then, another clipper system approaches from the northwest. Moisture appears to struggle, as is usual with these systems. However, when the cold front moves through, temperatures do appear conducive to more rain than snow. Initially, could also see some graupel mix in as strong low level lapse begin to form. Additionally, strong gusty winds 25 to 40 mph will be across the area ahead of the cold front. Gusts could briefly exceed 40 mph along the cold front Wednesday evening and then as the colder begins to come in behind the cold front, areas down wind of Lake MI (Berrien and Cass in Michigan and N Laporte and St Joseph in Indiana) could see winds surpass 40 mph overnight. Expect to see lake effect snow take shape during the evening and early overnight hours as a strong vigorous shortwave/secondary cold front approaches Lake MI. Delta T values approach 30 degrees with inversion heights up to 3 km/700 mb and lift through the DGZ. Those inversion heights do drop after 2am or so though to 2 to 2.5 km. Low level wind convergence becomes northwesterly with good RH through the layer. With strong gusty winds continuing overnight, the snow flakes could be ripped apart, which limits SLR/snow totals, but may act to arbitrarily lower visibility as is often the case with smaller snow flakes. Given the combination of moderate to heavy snow and the strong gusty winds leading to lower visibility, have decided to go with an impact-based winter storm watch for Berrien, Cass, and St Joseph. With the falling temperatures, there could be a refreeze problem in areas that roadways become wet. However, there's also the possibility that roadways stay dry with these clipper systems having the dry lower levels allowing for evaporation. Lake enhancement continues on Thursday as surface high pressure nudges in. Despite continued northwest trajectories, low level moisture begins to dry out, but it'll take its time. It likely continues at a light to moderate pace Thursday with temperatures at a similar magnitude to this morning, in the teens and low 20s. Continued northwest flow does look to keep high temperatures below freezing though. It may take until Thursday evening/night to finally shut off lake effect snow, though clouds may linger as northwest flow still continues. Another clipper system comes through Friday night and Saturday and that mainly looks to increase winds, but a dry airmass in place should keep the area devoid of precipitation. Then, with high pressure setting up across the Gulf of Mexico, it initially looks like the next system coming in Monday will be rain. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1229 AM EST Wed Dec 4 2024 Intermittent MVFR layer again over the area at the start of the TAF period. Conditions should become VFR by late morning ahead of a strong cold front that should move across the area between 23Z and 03Z. An initial rain/snow mix should become all snow as winds gusts increase to close to 40 knots. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...Winter Storm Watch from this evening through late Thursday night for MIZ078-079-177-277. MARINE...Small Craft Advisory until 4 PM EST this afternoon for LMZ043- 046. Gale Warning from 4 PM this afternoon to 1 PM EST Thursday for LMZ043-046. && $$ DISCUSSION...Roller AVIATION...Skipper