Light to Moderate Snow Across CT Tuesday Afternoon into Evening

Embedded pieces of shortwave energy in a fast jet stream flow aloft are set to dive south of CT during the afternoon and evening hours Tuesday.  In response to this energy an area of surface low pressure will develop and will produce a several hour period of light to moderate snows:

  While we aren't expecting a great deal of snow, the timing of the snowfall (afternoon through the evening hours) will yield a rather slow afternoon rush hour commute which will lead to numerous delays.  Extra care should be taken if out traveling.  There are some differences, however, in our computer forecast models on some features of the system and with that we see some differences as to the extent of the water liquid equivalent which will fall.  While the NAM, GFS, and European computer forecast models all agree that a weak area of surface low pressure will develop and pass just to the south of CT, there is disagreement with a potential feature called an inverted trough.  Typically, in the northern hemisphere, troughs are characterized by a southerly "bulge" or dip in the jet stream or height contours.  An inverted trough is characterized by a northerly bulge in the jet stream or height contours associated with a low pressure system or when height contours have a westward kink in them.  The NAM computer forecast model is a bit more more prominent than the GFS computer forecast model and much more prominent than the Euro computer forecast model and thus indicates a higher likelihood for a longer duration of moderate snowfall:

 With this system being on the weaker side we will not see a fully mature system develop and with this the degree of mid-level lift will not be all that intense.  The majority of the lift will be due to low-level processes with the main contributor coming from surface and low-level convergence.  One factor that will preclude the potential for heavy snowfall and higher accumulations will be the lack of solid snow growth.  Taking a look at the 12z NAM and GFS computer forecast model bufkit profiles for over Waterbury, CT we can see that the dendritic snowgrowth zone is not between the optimal height levels of 12,000' and 18,000'.  In fact, the zone is between about 8,000' and 13,000'.  While the NAM computer forecast model shows some pretty decent upward vertical motion (suggestive of good lift) and this vertical motion intersecting the dendritic snowgrowth zone (the GFS isn't as impressive with the degree of upward vertical motion) along with the -15C temperature contour dissecting this zone, the fact that the dendritic snowgrowth zone is so shallow will preclude the giant snowflakes which accumulate quickly from developing in the upper atmosphere.  This means we will see snowflakes which are mainly on the smaller side.  Snowgrowth is optimized when the dendritic snowgrowth zone is positioned between 12,000' and 18,000' and strong upward vertical motion is present within this zone with the -15C isotherm dissecting through this zone:

What can we expect tomorrow?  Light snows should begin to breakout sometime during the early afternoon hours with intensity beginning to vary between light and moderate through the rest of the afternoon hours into mid-evening.  While snowfall rates should not be all that heavy (at most 0.5'/hr) the timing of the snows will still yield to a slow afternoon and rush hour commute leading to delays.  Snowfall amounts should generally range between 1-2'' state wide (perhaps some mixing with sleet or rain along the immediate shoreline if the system tracks a little further north) if the inverted trough feature becomes as established as the NAM suggests and/or the system tracks further northward, some areas could pick up as much as 3-4'' of snow.  This will have to be watched closely over the next 24-hours.  Below is my snowfall map: