Saturday, January 18, 2020 CT Snowfall Forecast

I would like to begin by saying my notion of a "major" snowstorm for CT a few days ago was a bit misleading. Probably not the proper term to use for this type of setup, however, at the time I was not discounting the fact that there could potentiality be widespread 6''+ of snow.

Anyways, the forecast for accumulating snow Saturday is on track. This will be a very quick moving system and the majority of the state should even remain all snow throughout the duration of the event (with exception of the southern half of the state).

Normally, I wouldn't be as aggressive in terms of my snowfall forecast for such a setup, however, there are several things I like about this setup which I think will favor a bit more of snow then we would typically see. I will briefly go through these below:

1) Dynamic cooling - As low-level dynamics increase with this system this results in air rapidly rising upwards. This process results in cooling temperatures. When this process occurs rapidly there can be a rapid response in temperature. This will help with better snow ratios (see below) and preventing a changeover from snow to sleet (especially away from the shoreline). The GIF below illustrates how temperatures at 850mb (~5,000 feet above the ground) change during the day Saturday...notice how they cool quite a bit! Typically in this setup they would warm:

2) Favorable snow ratios - Typically in these setups our snowfall ratios are less than stellar...around 8:1 or so. However, given how cold the air mass will be (along with my expectation for some modest-to-decent lift into the dendritic snow growth zone...see below) I am thinking snow ratios may be as good as 15:1. This would indicate fluffy snow and possibly medium-to-large dendrites...the kind of snowflakes which accumulate quickly. Caution should always be advised when assessing snowfall ratios outside of 36-hours and with snow ratios on bufkit, however, the signal has been strong for solid snowfall ratios and given the environment I am inclined to believe they will be as good as 15:1 which is indicated below:

3) Forecast models are hinting at some decent lift penetrating the dendritic snow growth zone. This is also something which I think may trend a bit more impressive over the next 24-36 hours.

What can we expect?

• Snow begins to break out by late Saturday morning
• A 2-4 hour period of moderate to even heavy snow is possible mid-to-late Saturday afternoon
• During this period snowfall rates may approach 1.5'' per hour 
• Low-to-moderate travel impacts Saturday afternoon 
• Mixing with sleet southern half of the state...perhaps even to rain along the immediate shoreline
• Snow exits by late Saturday evening