December 4-9 Major Snow Event Discussion (Updated 11/30)

Bear in mind track is not set in stone and will likely shift before event occurs.

The models continue to shift northward, and because the GFS is moving towards the ECMWF solution, as are the ensembles, we have deemed it appropriate to make a rough sketch of a graphic. We are expecting a strong ridge of high pressure to hold in place on the East Coast and also keep much of the East warmer. This ridge will be pulling in warm, moist air from the Gulf of Mexico, creating an apt environment for some showers, depending on the moisture amount when the system comes through. To the west of the storm track, a cold blast of air may come down from portions of Canada in the wake of this storm. As this storm moves towards the north, a potential cold front extending from it will likely push away the warmer air and also help along the colder air. On the bottom side of the storm track, rain is widely expected thanks to the massive ridge in the East. This system will be grabbing the warm air and using it as moisture, which may help along the snowfall and rainfall totals in the end. For areas on the north side of this system, snow will occur. It is expected that the heaviest snowfall totals will occur right next to the track itself, where the moisture bands will be the tightest swirling around the low. This colder air that may also be in place would help the potential for snow as well.
The reason why this storm is not going south is because of the ridge and the cold air. It is a 'sandwich' situation, with two factors on the outside and the storm in the middle. The stronger component (ridge or cold air) will be the more determining factor for this storm. At this point, it appears that the ridge will be stronger and thus will push the storm farther west and north. If, for some reason, the models backtrack and decide that the ridge will be much weaker, then the storm track would likely short farther south. What is interesting about that is how the GEM model is following that potential of a stronger cold blast.
What may also be a factor is how fast the storm moves, and may play a bigger part than we may be noticing. The GEM has the storm track more south because that cold blast is coming out first instead of the storm as the storm moves slower and is thus pushed south. The ECMWF moves very fast, much faster than some other models. Thus, the storm comes first rather than the cold air. This would be a lose-lose situation, because less snow would fall and more rain would fall as the storm moves faster and is actually a bit north of the forecast graphic above.
We are consulting with other weather enthusiasts for their take on the storm track, so if you have anything to offer, drop a comment below- we'll respond to any questions you have.

Remember- this graphic is nowhere near set in stone, and was created to show current model guidance. The situation will change, and it looks like the situation should get itself intact going into the weekend.

Briefing on Dec. 4-8 snowstorm at 5:00 pm CST

There will be a new briefing on the December 4-8 snowstorm this afternoon with big developments at 5:00 PM CST.

GFS Ensembles Blast Country With Frigid Air

From PoliClimate. Legend superimposed by me.

GFS ensembles are forecasting brutally cold air to come down from the south in droves as Old Man Winter aims to make his presence known. Most of the ensembles are showing extremely cold air, while others show not as bad temperature anomalies but still well below average across the board. The 12th ensemble in the mix (counting from right to left) breaks the lowest this legend can go for below normal temperature anomalies. That's right, that ensemble member has temperatures forecasted to be at least 42 degrees below normal. That would certainly go below 0 degrees Fahrenheit.  However, this is hour 240 of the forecast, considered long range. We will monitor this prospect however, and keep you informed nonetheless.

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As of 9:40 PM CST: Blogger is having some issues that we are experiencing. At this point some trouble is being reported. We will be making updates on our Facebook page on the situation.

December 4-9 Major Snow Event (Updated 11/29)

12z ECMWF Snowfall

12z NOGAPS Ensembles with outlined areas. Lines inside the outlined portion indicate a possible track.

12z NCEP Ensembles. Tracks inside the black lines are possible ensemble tracks.

12z GFS (red) and 12z GEM (pink)

The Midwest remains in the potential line of fire for a major winter storm heading into the December 4-9 timeframe. The first image details the ECMWF's solution. The ECMWF continues to keep north, not budging at this time. Snowfall accumulations would easily rise above 6 inches in this scenario that the ECMWF is showing.
The second image is made up of the 12z NOGAPS model ensembles. At this time, pay attention to the models that are inside the black lines. Those are the models that are tracking this storm. The NOGAPS ensembles are keeping on the southern track at this time, which is somewhat surprising considering the NOGAPS itself is on a more northerly track at this time. However, because the models are not too good at this time, we are more angled to trust the ensembles.
The third image details the NCEP ensembles. Again, pay attention to the tracks inside the black lines. The NCEP ensembles are following the GFS, but at this time appear to be a tad more southerly than the actual GFS. We are again more apt to go to the ensembles at this time of model mayhem.
The fourth image is comprised of the 12 GFS and 12z GEM models. The GEM/GFS appear to be on a similar track until Illinois, when the GEM dips south as the GFS continues a northeast track.
All that said, here's the current camps of north track and south track.
The north track is above North Illinois, while the south track is below North Illinois.
(ENS. stands for ensembles)

North Camp: NOGAPS, ECMWF, DGEX, JMA, ECMWF Ensembles
South Camp: GFS, NOGAPS Ensembles, NCEP Ensembles, GFS Ensembles, GEM, GEM Ensembles

Ratio of North Camp to South Camp is 5:6 out of 11 models in favor of the South Track.

It does look like a ridge in the east and a cold outbreak in the North Plains will be two key factors in this storm track. The ECMWF pushes the warmer air farther westward, thus bringing the storm track in the same direction. The 12z GFS is more forceful with the cold air and keeps the storm track down south. However, the GFS has started to trend north, as illustrated in the below picture:

Past 4 cycles of GFS (see color key on bottom right)

The GFS, as you can see, has been very stable the last couple runs but has trended north for one run. We are waiting for the 0z run to see if this change will continue or if this run was a fluke.

We are thinking that a blend of the ECMWF/GFS is a good idea at this point, but definitely leaning with the ensembles as the models struggle in some spots.

If you want to see the models for yourselves, check out our updated Weather Models Page, now housing 144 links for 25 models.