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LIVING ON THE EDGE (of a snowstorm)...

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If we were playing horseshoes, we'd be in the game for a big snow maker but close doesn't necessarily count (or for that matter cut it) in the game of snowstorms. You don't need to throw ringers, but you better get close enough to the post to pile up some points, in this case inches of snow. What we are facing with the coming storm is a situation where very dry air will challenge the saturation process on the edge of the snow band. In a very short distance of a county or so amounts could vary from a dusting on one end to 3 on the other. Within my area, amounts could go from nothing in the far northeast to 6 inches in the far southwest. The challenge is determining where that wall of dry air sets up, how it impacts the track of the storm, and influences snow totals.

Even if all the models showed the same thing (which they don't), I would still be worried about this forecast due to the abrupt nature of the cut-off. You are basically in or out for snow and the inability of models to accurately see and portray the "dry punch" means the potential for a bust exists in the transition zone near the Mississippi. I'm far more worried about that than forecasting the actual amounts which is often the biggest hurdle in a winter storm. It's all a big puzzle and right now a few pieces are still missing with less than two days to lift off.

All of these issues are the result of a huge 1043mb high pressure just north of Lake Superior. The stronger it is and the further south it presses will determine our fate. Acting as a block in the atmospheric river, the storm itself will take the path of least resistance and head for more favorable dynamics to sustain itself as it scoots across the country. For a time, this thing is moving almost due south which gives me a solid clue that high is a formidable block.

In the animation below you can observe the forecast track. Watch as the storm dives south out of Canada into Texas where it reaches the southern extent of the highs ridge and then curves back to the northeast once the highs influence is negated. Pretty fascinating stuff if you are me.

I mentioned above that the models all have their own opinion about how far northeast the snow band gets in my area. Otherwise they are all in large scale agreement about how the system is going to perform. It's just unfortunate that my area is right in the middle of the battle zone leaving us with what is still a somewhat low confidence forecast while east or west of here, confidence is actually high. So before I get to the latest models and their snow output, here's what's currently indicated, or in place from the NWS and the Weather Prediction Center. First, the winter storm watch. This is the zone which currently stands the best chance of seeing significant snow accumulations late Friday and Friday night. It's only a watch at this time because details are uncertain.

The Weather Prediction Center shows these odds for at least an inch of snow for the time being. You'll notice it's west of the Mississippi and into Iowa where the core of the storm is most likely. That's not likely to change much going forward.

These are the odds of 4 or more inches.

The winter storm severity index looks like this. Depending on the track this could extend further east or west at some point Thursday.

In advance of all this, Thursday should be another decent day. There may be a few isolated snow showers or flurries but models have really backed off in QPF since yesterday (which wasn't much to begin with) so this is hardly worth a mention. Otherwise, skies should be mostly cloudy and with northerly winds temperature will cool into the mid to upper 30s. The calm before somebody's storm.

The storm itself is not anticipated to arrive until Friday afternoon, Friday night and early Saturday is when the greatest impacts are expected. No doubt worse the further west you go, especially in Iowa. Highs Friday in advance of the snow should generally be in the mid to upper 20s, maybe 30 in the far south.

That brings us to the main event and here's what the latest models are showing. With 36 hours before the storm any solution is far from certain, especially with the issues that need to yet be resolved with the dry air. Also, a reminder that these are not forecasts, just raw model output. These and newer model runs will act as guides for official totals, warnings, and advisories that will be issued later Thursday. What I have noticed is that consistently the EURO has been further west and lighter with snow amounts. The GFS has been just as adamant in it's further east and heavier depiction. A recent trend was for models such as the 12 and 3K NAM to inch closer to what the GFS has been advertising. The GEM is also in that camp. While the EURO is still furthest west with the snow band amounts have reached the 2" threshold as far east as the Quad Cities. It does seem there's a little give and take going on which I hope will get us some good consistency Thursday and a higher level of confidence on precise totals. Here's what I've got to show you. My thoughts will follow the output.

The EURO (the least impactful model for my area, especially across the east).

The GFS (it and the 12K NAM are the most impactful and furthest east with snow accumulations).

The 12K NAM

The 3K NAM


It's clear for all to see that the worst of this system is going to be west of the Mississippi. What happens in Illinois is still very much an open question, especially in my counties surrounding the river. I do think the potential for 3-5 inch totals is real in the western third of my area, especially out around Iowa City and Cedar Rapids. In the Quad Cities and surrounding region 1-2 inches is the way I'm leaning, with an inch or less in my far northeast counties, especially beyond Morrison and Sterling. That's just based on what I've seen Wednesday night so that's very preliminary and Thursday's models could show additional variations in these trends. At least it's a start. For my money, I still like the lower and westward solutions of the EURO. Dry air is a real tough commodity to battle and I suspect the majority of my area will just get a glancing blow from what will be a potent snow maker just to the west in central Iowa.

Whatever happens, temperature readings behind this system should be seasonal or below normal for much of the next week. Beyond that, guidance is pretty consistent showing the positive PNA continuing which is very conducive for cold. The EURO 8-15 day temperature departures look like this during the 7 day period January 20-27th. A very cold look for the entire country!

Well, now we hurry up and wait for the new data that will determine our fate. One thing's for sure, from my far western counties back into Iowa this has the makings of a decent winter storm with heavy snow and even enough wind to blow it around. To my friends out west, please enjoy it for me. More to come. Roll weather...TS


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