01/19/2019 to 01/20/2019 CT Winter Storm

We have been tracking the potential for a rather significant winter storm for several-plus days and as we get closer to the weekend this potential not only still exists but the potential is becoming more of a reality. Before I get into the posts I wanted to post a disclaimer. All images that will be posted (unless otherwise noted) will be from the GFS forecast model. I can't post images from the European model as I don't have permissions. Just because I'm posting GFS graphics does not mean I am leaning toward's that model...what I am posting is to just illustrate. 

There are three key features that will be involved; a thermal boundary, southern stream vorticity, and northern stream vorticity. An area of low pressure (perhaps multiple low pressure circulations) will develop along the thermal boundary and strengthen with aid from vigorous vorticity:

There are substantial differences between the GFS and European forecast models with regards to the evolution of the southern stream energy which will play a substantial role in the eventual outcome of this system. The GFS is much stronger or "amped" than the European forecast model. This yields the surface low pressure to actually track either over CT or perhaps slightly west. This solution would yield a snow, to ice, to rain scenario. The Euro not being as amped is slightly farther southeast with the track of the surface low and would result in a snow to potentially significant icing situation across CT. 

Forecast models indicate some very high precipitable water values (PWATS) pushing into the area and feeding into the storm. PWAT values just south of the area are forecasted to be well over 1''...that is suggestive of very juicy air. A very strong temperature gradient will also exist over southern New England which will help to enhance frontogenesis over the region and support vigorous lift. This is shown with the vigorous 700mb vertical velocity values. Very strong warm-air advection (WAA) will further assist in the lift process:

This grab from the 18z GFS is the bufkit overview for Windsor Locks, CT. This is showing exceptional lift overnight Saturday...despite the most intense lift well below the dendritic snowgrowth zone this still shows -20 to -30 units of omega within the zone. Snowfall rates will approach 2-4'' per hour at times during the height of the snowfall:

We will have to carefully watch the exact track of the surface low as the likelihood exists for snow to changeover to freezing rain, sleet, and potentially rain. While the GFS forecast model is not very aggressive with freezing rain here, the European model is. There will be a tremendous amount of cold air just north of us and if the surface wind direction is more northerly as opposed to southerly or easterly this cold air will drain down the CT River Valley. This would keep surface temperatures well below freezing while temperatures a few thousand feet off the ground warm above-freezing...this would result in freezing rain and the potential for significant freezing rain.

Below is what I am currently anticipating in terms of impacts for CT.