Chaos Ensues, Winter Storm Uncertain
By Justin Poublon
December 19, 2017 - 12:00 PM CST | 82 0
There has been lots of talk about the late week storm for Thursday-Friday. Latest model guidance has trended much weaker, slightly southeast with this event over the last 24 hours. The forecast has become more uncertain over the last 24 hours. I woke up this morning expecting to set this winter storm solidified but now it's all over the place! Good thing we waited to post snowfall predictions, yeah?
WHAT'S GOIN' ON?
A low pressure system will drop southeast out of the pacific northwest tomorrow and dig into the central plains. Light accumulating snow will develop across northern Minnesota through Duluth and into the upper Michigan peninsula on Wednesday night.
Initially the storm is strong and healthy but as it digs south and fires through the great lakes it loses it's oomph. The forecast becomes uncertain Friday with the 19-12Z GFS forecast model introducing a new wrinkle similar to the Canadian wrinkle we mentioned yesterday. This wrinkle is to develop a strong low pressure system well south and send it through lower Michigan.
It's starting to look like this historical analog I mentioned on Sunday with incoincident regions of snow accumulation. Maybe southeast Wisconsin gets a bunch of snow on Friday night?
I will focus on Wednesday night through Thursday and even that remains a tough task.
Wednesday PM through Thursday I predict 2-5" for northern and central Wisconsin. This would be a two-part event with the far northwest Wisconsin getting snow Wednesday to Thursday morning, and the second round firing up across central and southern Wisconsin Thursday. If weakening trends continue, expect less snow. Model predictions showed accumulations of 12-15" for north-central Wisconsin yesterday during this time period! Below is my current snowfall prediction map. I promise this will change by tomorrow, this is just to provide a general idea.
and wow, how things can change...
We will be monitoring the potential for light ice or freezing rain in southern Wisconsin on Thursday as well. Again, if the latest GFS is correct then we will have another snow event for Friday into Saturday. Unfortunately we will have to wait until we can build consistency again. Who knows at this point. Euro is weaker. Canadian is further south. Maybe the GFS and NAM trend stronger in the final 48 hours?
I still believe the big story will be the harsh cold arriving before, for, and after Christmas. Sub-zero high temperatures will be possible one or more days next week, colder north and near fresh snow cover. High temperatures for Christmas day in central Wisconsin are forecast to be sub-zero right now. Details are prone to change but the cold will be uncorked.
With the chaos that is the Friday-Sat period even I'm not sure how certain I can be about this. The same GFS model is trying to shove a snowstorm through central Wisconsin late in the week. I don't mind this actually because it makes sense with the natural progression. I do believe the long term pattern is a stormy one. If we miss our first major storm this time, we will have more chances maybe even before the end of 2017. La nina's reach their peak impact in January and February.
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