Monday, December 30, 2013

January 1-3 Significant Winter Storm - Part I (Midwest, Great Lakes)

This post will address the first part of the January 1-3 winter storm, where anomalously strong clipper system will lay down significant snows in portions of the Midwest and Great Lakes. You can find the link to Part II, which addresses the effects on the Northeast, at the bottom of this post.

Global model guidance is in agreement with an Alberta Clipper system dropping down from Canada and traversing the Plains to enter the Midwest. Model discrepancies begin to evolve early on, namely when the NAM model takes the snow swath unusually far north into Central Wisconsin. More recent runs of that model have corrected southward back towards Southern Wisconsin and Northern Illinois, but that model will still have to be monitored. GFS/GGEM/ECMWF models hold the consensus with this super-charged clipper, as all three bring about significant snows stretching from Iowa to Chicago back into portions of Indiana and near Ohio.

Global model guidance has been putting down liquid amounts around 0.6" to even 1.0" in northern Illinois into Michigan, and it is those areas highlighted above by the ECMWF that we are monitoring in this post. This event is actually a combination of as many as three different clipper events, with the third one bringing the most snow around New Year's Day. Because they're clippers, right off the bat we are going to most likely see higher snow-to-liquid ratios than usual. A typical snowfall has a 10:1 ratio, which means 10 inches of snow could be melted down into 1 inch of water. In this case, however, we're thinking that places like Chicago could see snow ratios of 15:1 or even 18:1, which means 1 inch of water could theoretically be fluffed up into 18 inches of snow. The ECMWF model above gives downtown Chicago 1" of precipitation, thanks to some additional lake enhancement, and if we were to use a 15:1 ratio throughout the whole event, maybe ending on higher ratios in response to possible lake enhancement, I could envision up to 15-17" of snow. Realistically, that is unlikely to happen. I find the ECMWF to be too bullish (overdone with precipitation) for my liking. The GFS/GGEM seem slightly more in line, with amounts closer to 8-15" being produced. This event would be a significant one if it were to verify as it stands right now. And while I don't trust the 15"+ forecast being implied by the ECMWF, it is theoretically within the realm of possibility.

My thinking for this part of the event is that the areas of southern Wisconsin, northern Illinois, northern Indiana, southern Michigan and northern Ohio will receive heavy snowfall from this system. Based on current model projections, I would issue a call for 10-15" for those areas (with potentially higher isolated amounts), but based on a slight concern models may draw back on QPF projections (quantitative precipitation forecasts, also known as precipitation forecasts), I'll go with a conservative 8-12" for the aforementioned regions, with the very possible chance for higher amounts.

For Part II of the January 1-3 Significant Winter Storm, please click here.



Wally Gullang Huntley, Ill. said...

Tom Skilling with WGN-TV in Chicago is now calling for up to 10" Northwest of the city with lesser amounts in the city with possible lake effect for the city itself for the same time period

Dean said...

What are you predicting for Central Ohio? I live in newark(just a little northeast to columbus)


Anonymous said...

Local weather calling for 2-4 inches in northern Illinois. Nowhere near 8-10. Love the site though