A current look at the northern hemisphere reveals that a transient 50/50 low is allowing enough cold air into the eastern US for a storm system approaching the Atlantic seaboard to produce a swath of light to moderate snow from the Washington DC region south into parts of the Carolinas. Elsewhere, ridging is building off the west coast of the US which is forcing a trough to develop over the western US. This ridging will continue to build off the west coast, leading to a trough developing over much of the western/central US over the coming days.

As the ridging builds into Alaska in the coming days and becomes a –EPO block, temporarily, cold will build over Canada and will slowly seep southward into the northern portions of the US. At the same time, the trough will slowly move east from the western US, leading to several systems tracking across the northern US that will produce rain and swaths of light snow.

The European model ensemble mean, valid Wednesday morning, shows this transition well, with the ridging off the western coast of the US resulting in a NW flow into the northern Rockies and Plains. Because of the lack of blocking over the arctic/high latitudes, this trough will be transient, meaning it won’t remain in one place for too long. This will result in the trough being deepest over the Great Lakes region to end the week, where the best chance for multiple nuisance snow events will exist.

The best chance for any notable snows will come at the end of the week, when a piece of moist subtropical jet-stream energy, seen on the above image by the lower heights over the Baja of California, moves east and attempts to interact with the building trough and cold air over the Great Lakes.

The European model, shown above, develops a very strong low pressure late Friday into Saturday over eastern New England as it phases the subtropical jet stream energy with the trough over the Great Lakes. The European model showed a large area of 6”+ snow totals with this storm from Upstate New York east into much of New England. The question is, is the European model’s solution a viable one?

Back to the European model ensembles in the day leading up to the potential storm, there are a few things that point against the wound up operational Euro’s solution.

1. The strongest ridging is extending up into western Alaska. This is farther west than what those of us in the northeastern US would like to see, because it favors lower than normal heights over the western US, which does not support a deep, sustained trough over the eastern US.
2. There are lower than normal heights over Greenland, which again does not support a deep or sustained trough over the eastern US.

By 144 hours, a shortwave is digging on the west coast and the trough over the eastern US/Great Lakes is already dampening out, the flow is trying to become zonal.

The ensembles do develop a storm in this time frame, but show it tracking farther east than the operational European model…they also show a weaker solution, but because the ensemble mean or average is shown, this does not necessarily mean that some ensemble members are not also showing a deep storm in this timeframe:

However, because of an unfavorable Atlantic and Pacific for a significant snowstorm over Upstate New York and New England in this timeframe, I believe the European model solution that was very deep and farther west with this storm is an unlikely solution. A more likely solution is a weaker frontal wave of low pressure with much lighter snows behind the cold front over the Great Lakes Friday and New England on Saturday, with some potential lake effect snow in the Great Lake Snow Belts.

The individual GFS ensemble members from Sunday afternoon agree with this…while many members do show a wave of low pressure riding up the front Friday into Saturday, most members (excluding one) show a much weaker solution than the operational European model:

I will continue to monitor this potential end of the week storm and a threat to start next week in the coming days. Enjoy your Monday,

Jim.