First Lake Effect of Season This Weekend

Quick summary of my thoughts on potential lake effect snow downwind of most Great Lakes this weekend:

Off of Lake Superior, I’m thinking that winds changing through the event will keep accumulations under control. A little trough drops south across the Lake and should cause activity to intensify this evening…850mb temps of -8 to -10C and 925mb temps of -2 to -3C should easily support accums in the higher terrain. The activity may swing west towards MQT for a time tonight, and the more northerly flow for a few hours behind the trough should hit the higher terrain west of MQT for a time tonight. The winds go more NW by Saturday morning which should shift the bulk of the activity east of MQT. The winds never stop shifting completely so I think 1-3″ in the higher terrain east of MQT in Alger county should about do it…maybe a half inch in the higher terrain west of MQT.

Off of Lake Michigan conditions become very favorable for decent lake effect this evening as the same trough drops through. Winds will initially be NNW which should hit areas between Traverse City and Gaylord, but will go more due N late tonight behind the trough which should shift things to just S and W of Traverse City. Winds start backing on Saturday to WNW and then whip around to the N again Saturday night as inversions start coming down…overall think maybe 1-2″ in the higher terrain where the bands affect over the next two nights, winds look too variable for a band to sit and allow for better accumulations.

Off of Lake Huron I’m more intrigued…the winds look like they’ll hardly move from late tonight through late Saturday afternoon with extreme lake induced instability (CAPE on the order of 1000 J/KG+ from around midnight tonight through very early Sunday), very high equilibrium levels (15-20k feet through early Sunday) and deep moisture with help from upstream lakes (high RH air to near or above 10k feet late tonight through very early Sunday) in place. The winds are well aligned and will have the full fetch of the lake to work with. A very intense band with thunder and lightning is likely downwind of Lake Huron this evening through Saturday night, with little movement possible through much of the day Saturday. The winds will be NW late tonight through Saturday which I’d have to imagine supports the heaviest band staying just north/east of London, but I’m not a Lake Huron band expert.

Saturday evening the winds initially gain a more westerly component ahead of an approaching trough which should push any band farther east and possibly weaken it some for a few hours. The winds become decently well aligned for a few hours out of the NW again late Saturday night into early Sunday before becoming more northerly and pushing everything west. Instability and moisture slowly wane during the day Sunday which should cause a slow end to things.

Potential accums are definitely tough…with 925mb temps of -1C to -2C tonight, well aligned winds in the boundary layer on the order of 20-30 knots (not too strong) and a likely very strong band, I fully expect dynamical cooling to change precip over to snow tonight under any strong band. Temps warm a tad during the day Saturday, but assuming a band continues, it should remain all snow under it (maybe the lakeshore tries changing to rain during the afternoon?). Heavy wet snow will accumulate despite wet ground. There could be a 12 hour period tonight into Saturday where the band moves very little off of the southern end of the lake, and that could produce 6-10″. Things start moving around move Saturday evening through Sunday morning, but another 1-3″ could fall on spots very early Sunday if the winds can stabilize for a few hours. This could be a pretty significant event with a lot of tree damage.

Off of Lake Erie temperatures are a bit too warm in NE Ohio to get accums with this type of weaker multi-banded setup…maybe the higher terrain in Geauga or inland Ashtabula can get half an inch. In NW PA and perhaps into Chautauqua County in SW NY, there is more terrain and likely will be heavier precip rates beneath a likely Huron-Erie connection. It will take until later tonight for temps to support accumulating snows in the higher terrains, but there should be a few hours of fairly steady banding in central/eastern portions of Erie/Crawford Counties in NW PA, with likely accums in the higher terrain with 925mb temps of near -1C and extreme lake induced instability and moisture from Lake Huron supporting a moderate to heavy band. Winds here also shift more WNW for a time Saturday afternoon/evening before going more NNW for a time Saturday night before going WNW again Sunday morning. Think the shifting winds and slightly warmer mid-level temps during the day Saturday will keep additional accums Saturday afternoon fairly light…maybe another inch in the higher terrain. Late Saturday night into Sunday morning as the winds become more steady again from the NW or WNW, there could be a period of some accums, again probably in eastern Erie/Crawford counties in NW PA perhaps into Chautauqua County NW and perhaps into parts of Venego/Forest/Warren Counties. Overall due to less persistent banding and more marginal temps here I think maybe 2-4″ falls in the higher terrain. If a band persists for longer then maybe a local lolly to 6″ is possible.

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