Plowable Snows Likely Wednesday Across Connecticut

The weather pattern has certainly become much more active as we've entered the month of March and that trend will continue this upcoming week as there is continued growing confidence for plowable snowfall across the entire state of Connecticut this Wednesday. Computer forecast models have been in strong agreement for the past week on the possibility of a rather significant storm to impact the state o n Wednesday and that agreement continues. There is, however, some disagreement with regards to the exact track of the storm and this will ultimately affect exactly how much snow we see, where the heaviest banding/highest snowfall totals occur (and whether this happens to be somewhere in Connecticut), and where we see an area of subsidence which would mean reduced snowfall totals somewhere. Over the course of the next 24-36 hours these questions should be resolved.

We are watching two key pieces of energy which are expected to phase and once they phase the result will be the development and cyclogenesis (rapid strengthening) of a low pressure just off the coast of the Carolina's where surface convergence and upper-level divergence will be favored:

As the storm works up the coast there is some uncertainties with regards to exactly how close to Connecticut the storm tracks. Some of the forecast models track the storm farther off to the east. This result would mean the heaviest snows likely being confined to central and eastern Connecticut and also a reduced possibility for mixing along the southeast coast. Other forecast models are farther west with the track and this result would mean heavy snows across western and central Connecticut...perhaps even the heaviest occurring in eastern New York and northwestern Connecticut and a higher likelihood for mixing across southeastern Connecticut. These details will be ironed out over the next 24-36 hours.

Most forecast models develop an extremely potent storm with the potential for extreme upward vertical motion with this storm. This indicates that there will likely be a zone of extremely heavy and intense snowfall, the question just is where does that occur? This is the biggest question/challenge at hand with regards to snowfall forecast. We will examine below:

The NAM also indicates that the best frontogenesis (strengthening of horizontal temperature gradient with height) would remain west of Connecticut with frontolysis (weakening of horizontal temperature gradient with height) moving into Connecticut late afternoon and early evening. This indicates that the heaviest snowfall and most extreme rates would be just to the west of Connecticut:

However, prior to frontolysis and perhaps as the system works east and the best frontogenesis pivots through western Connecticut we could see some extremely heavy banding and very heavy snowfall rates per the NAM and this indicated very well by some bufkit soundings. This bufkit profile over Waterbury Connecticut yields two windows for extremely heavy snowfall; one during the midday and the second during the early portion of the evening as the system is beginning to depart. This profile shows a very favorable snowgrowth zone with impressive omega (red contours indicate upward vertical motion) penetrating the snowgrowth zone. One possible question here though is would moisture be lacking in this zone and this questions arises with less than 90% relative humidity values within the dendritic snowgwoth zone:

Using the same image but with relative humidity overlayed this shows relative humidity values less than 90% within the dendritic snowgrowth zone. Not a major problem but this could be something which inhibits excellent snowgrowth a bit:

The GFS also shows substantial lift within the snowgrowth zone and even hints at the possibility of some subsidence within the lower levels looking at a bufkit sounding from Waterbury, CT:

The GFS also advertises rather strong vertically averaged 800-600mb frontogenesis over the entire state during the afternoon, however, like the NAM the frontogenesis weakens and we see frontolysis develop. This indicates that as we approach the early evening snowfall intensities could weaken before finally picking back up briefly as the system departs:

So as of now what can we expect?

The details mentioned within this post are all critical to how much snow we see, where the heaviest banding/highest snowfall totals set up, and whether or not we see any areas of reduced snowfall totals thanks to subsidence or weakened upward vertical motion. As these details become ironed out the snowfall map can be adjusted to account for these details.

• Light snows begin to break out between 11:00 PM Tuesday night and 2:00 AM Wednesday morning. 
• Snowfall intensity begins to increase in intensity by late Wednesday morning with a period of moderate to very heavy snowfall lasting through mid afternoon. During this time snowfall rates could approach 2-3'' per hour in the areas which are under the heaviest banding. 
• Between mid-afternoon and late afternoon there is the possibility of reduced snowfall intensities. This is due to the strongest frontogenesis and upward vertical motion perhaps pushing west and north of the state. This will have to be watched because a prolonged duration of this phenomena could result in lesser snowfall totals for many locations. If we don't see reduced snowfall intensities during this time this would result in the likelihood for even higher snowfall totals across many locations. 
• As we near the height of the storm, strong gusty winds will begin to develop thanks to a strengthening pressure gradient across the region. Winds could gust as high as 25-45 mph with the higher gusts occurring near the coast. 
• As the system begins to depart the back edge of the storm will begin pushing through and there is the potential for this band to be extremely heavy which could add to some of the snowfall totals. This is something which will also influence the potential for higher end snowfall totals. 
• There is the likelihood for snow to mix with sleet and rain across southeastern Connecticut and this will result in lesser totals here. There is also the possibility for some mixing to occur across the majority of the state during periods of lesser intensity if the storm tracks further west and we get an influx of warmer air in the boundary layer. 
• Snow begins to wind down during the mid to late evening hours.

Below is my fist call snowfall map. Keep in mind that this will likely be adjusted tomorrow as the details mentioned above become more clear: