Shortwave train

Main thing provoking a lack of a model consensus for the Sunday and Monday snow potential is the presence of numerous features that need to be monitored. In situations like these, the models tend to disagree on which wave becomes dominant.

Currently there are two camps: The ECMWF and NAM, and then basically every other model.

A broad based wave will move over the Great Lakes by Saturday night, with associated surface low pressure moving south from Canada. This surface low will be captured by the 500mb trough, with a weak wave and overrunning precipitation moving east across the region late Sunday morning. General consensus for this initial wave is for .3" to .5" QPF. This should translate to a 4" to 7" event through Sunday evening.

A stronger piece of energy will ride the trough south from Manitoba on Sunday. The ECMWF and NAM close off the 500mb trough over the Great Lakes, which then results in a broader curve to the H5 field, and a flatter, more progressive flow to its south. Combined with a stronger tailing shortwave, this squashes the second shortwave, sending surface low pressure safely east of the region. The GFS on the other hand has been consistent with a stronger piece of energy with a sharper trough and ridging out ahead, to send surface low pressure closer to the coast. This would deliver a second round of snow Monday morning. This part of the forecast is very uncertain however.

What does look good right now is the initial round on Sunday, which I think promises a moderate snowfall for much of CNE.