For snow-lovers to begin the next work-week, it just may be.

In previous blog posts, I discussed the trough that will eject from the west to end the month of February and the potential ramifications over the central and eastern US, which include a swath of accumulating snows and potentially severe weather.

The above capture of the 12z European model (ECMWF) ensemble means shows what the landscape will look like following the weekend storm over the northeast US that has been discussed in previous posts. The weekend storm, by most accounts, will deepen significantly over southeastern Canada and temporarily raise heights over the Davis Strait, allowing for a transient psuedo -NAO and 50/50 low to form Sunday before the fast nature of the pattern forces the NAO to return to a positive state and heights to rise over the eastern US.

At the same time, ridging will thumb its way into southern Alaska and help carve out a trough over the Rockies. This trough will eject east into the central and eventually northeastern US starting Sunday, but it now appears the trough will eject east in pieces, resulting in more than one low pressure riding through the northern tier of the central US/southern Canada as opposed to one large storm cutting through the upper Midwest.

The first piece of energy will eject Sunday and reach Ontario by Monday evening. As one would expect, there are some variable model solutions with this ejecting energy…

The 12z ECM shows a storm that ejects from the TX/OK Panhandle area and moves ENE into WI before deepening and cutting northeastward into the UP of MI by Monday evening. This solution would bring a swath of snow to the northern Plains east into northern IA, southern and eastern MN and a good chunk of WI and northern MI.

The 12z GFS was not much different than the 12z ECM in the end…the GFS is a bit north with the low track early on and does not cut the low to the northwest of the Great Lakes as sharply as the ECM does, but the end tracks and end results are not too far off. It should be noted however that the GFS is several hours faster in taking the low pressure east than the ECM.

The 12z GFS ensembles however show more variation than the operational GFS/ECM have in their solutions. The ensembles show a wide range of solutions, from a weaker storm that ejects faster and tracks a bit farther south, to a wound up solution over the western lakes by Monday morning like the operational models are currently showing, to in one case almost no storm at all.

The 12z ECM ensemble mean shows a solution that is a bit faster and a bit flatter than both of the operational models, which seems to be the trend amongst the GFS ensembles as well, sans a few members.

So, what solution is most likely?

My initial inclination would be to expect the slightly more progressive (faster) and farther south solution with less of a hook north into Lake Superior than the operational models show. When referencing the large scale pattern shown in the European model ensemble mean to open the post, my logic is fairly simple:

Although brief, confluence from the departing storm over eastern Canada will favor a high pressure over south-central Canada that will make it hard for a storm to hook north.

However, there are some factors that may allow for the more NW track to win out…

The 12z GFS, shown above, was close to digging the northern stream shortwave far enough south to partially phase with the subtropical jet stream energy. If phasing were to occur, the jet streak would intensify, divergence in the left-exit portion of the jet streak (which the SLP will be co-located with) would increase and the storm would intensify faster, allowing the shortwave associated with the storm to take on a negative tilt west of the lakes and allow for a nice left-hook in the surface low track

As also noted above, the NAO will quickly return to a positive state by Monday and southeast ridging will try to develop. This may allow heights east of the Great Lakes to rise enough to help the storm take on a negative tilt west of the Great Lakes.

Given seasonal trends and the fast nature of the pattern, I will for now favor the less amplified solution which may allow good snows to get into much of IA/WI/MI Sunday night into Monday, however we will need to watch for a potential partial phase between the northern and southern branches of the jet stream and rising heights east of the Great Lakes, as those factors may allow for the more amplified solution to play out.

The very cold air and Canadian high pressure just north of the surface low should allow for a nice band of powdery snows and high winds to the north/west of the low track in either solution.

More tomorrow,

Jim.