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After the day we had Wednesday (50s areawide), it's tough to believe that the focus of the forecast two days from now will be centered on snow and wintry weather. However, the trends in all the data indicate a storm (high confidence) will cut across Missouri and Illinois. That puts my area in the cold sector and with cooling aloft Friday night and into Saturday rain in most areas will change to snow with the potential for some heavy wet accumulations possible.

The Weather Prediction Center already show odds of 60-70 percent for at least an inch of snow across the NW half of my area. That's a little further north than yesterday owing to the depth of the cold air which models are still attempting to determine.

The first winter storm severity index indicates from EC Iowa into NW Illinois and SE Wisconsin moderate impacts, the typical issues you would expect with a 3-7" snow.

As I indicated last night, there is a split in the northern and southern streams which inhibits full phasing of the storm. Depending on your position, that can be a good or bad thing because if the two really got it together with a stronger intrusion of cold air, this could have been a pretty wrapped up storm. As it is, there will be just enough cold air to get a snow band going somewhere in my area...still some fine tuning to do on amounts and location. In the 500mb depiction Saturday on the EURO you can see the two streams, one in Canada and the other cutting across Kansas and Missouri, not quite in unison.

That drives a surface low on an E/NE track that takes it near St. Louis and just south of Springfield, Illinois. That's a benchmark track I look for in a snow system in my area.

My biggest concerns with the system now are centered on phasing and the transition from rain to snow. If there is a bit more phasing than models currently see, that could cause enough intensification to bring the surface low a bit further northwest and draw just enough warm air to delay the transition from rain to snow in the southeast half of my area, especially near and south of the Quad Cities. That could decrease amounts in that part of my region and raise them in the NW.

Additionally, even less phasing and the system goes further south with minimal impacts. The GFS is hinting at that possibility. Right now I think the GFS is an outlier and I'm leaning toward the EURO and GEM snowfall solutions which are significantly higher. All 3 are posted below. I do want to stress there is still room for change and confidence is only low to moderate in any outcome. What you are looking at below is raw model output and not a forecast, this is just the data we look at to make a forecast when the time comes..


The GEM (Canadian)

The GFS....At least for now this seems questionable and I think amounts are well underdone. Thursday will be a big day for modeling and hopefully we can get some better consistency in track, intensity, and snow potential.

One last thing, before all this arrives Friday afternoon through Saturday, we have another fine day to enjoy. There may be some patchy fog around early Thursday but sun should emerge and highs again should head into the low 50s. Another keeper. Enjoy, for many of you it should look a lot more like Christmas by the end of the weekend. Roll weather...TS


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