Sunday, December 1, 2019 - Monday, December 2, 2019 Snow Potential

Are we looking at our first accumulating snowfall event for the majority of CT as we turn the calendar to December? There continue to be growing signals that this may be a possibility, however, there are still numerous details to iron out moving into the weekend. This is going to be a bit of a messy storm as there will be two different parts to it. This will also be drawn out over the span of a few days. (Note: I use GFS graphics for visual reference, however, analysis and my thoughts are derived from analyzing all forecast models).

They piece of energy which will be responsible for our potential storm Sunday and Monday is entering the southwestern U.S. This energy will also be a player in what will be a significant winter storm/blizzard across the Inter-mountain West, northern Plains, and Inter-mountain West moving into the weekend:

Sunday morning, the piece of energy is forecast to dive southeast through the Ohio Valley. At the surface an area of low pressure (weakening) will be moving towards the east-southeast. As this whole system progresses towards the east-southeast a warm front will lift towards southern New England. As the warm front approaches, warm-air advection will rapidly increase. This warm-air advection will be quite significant as it will result in a period (perhaps several hours) of moderate-to-heavy snow overspreading much of the state. As warmer air begins to arrive (first occurring a few thousand feet off the ground) snow will quickly transition over to some sleet (maybe some freezing rain) and even rain along the immediate shore. This will conclude part one of this system:

Moderate-to-heavy snow overspreads the state Monday morning before transitioning over to a wintry mix and rain along the shore by late afternoon. Several inches of accumulation will be possible:

As the energy dives south of CT Monday morning, a secondary area of low pressure is expected to develop...this is where things get a bit dicey as it's uncertain exactly where this happens and how quickly this happens. Prior to this development, warmer air will be in place, both aloft and at the surface, thanks to the warm-air advection. However, as the secondary low develops and strengthens dynamic cooling will take place and this will allow the lower-levels of the atmosphere to quickly cool with colder air working in at the surface.

My current thinking is this all happens a bit too far north. This will keep the column a bit too warm for snow here in CT (although a better chance would exist in the northwest hills and along the CT/MA border) and we'll see mostly rain or a mix with this second part. Although, this is still several days away and plenty can certainly change.

All in all this system will likely be a major snow producer (8-12''+) somewhere in New England, it's just uncertain as to where this area will be. My early estimate is along and north of the MA Pike.

Sunday, December 1, 2019 Forecast:

• Snow begins working into the state from west-to-east during the morning. 
• Snow quickly picks up in intensity; perhaps falling at rates of 1-1.5'' per hour.
• Snow begins to change over quickly to rain rain along the immediate shoreline first due to the influences of the warmer water. 
• Snow transitions over to a mixture of sleet...perhaps some freezing rain and rain inland as warmer air begins to work in aloft.
• Significant travel impacts expected beginning late Sunday morning into the evening.
• Winds do begin to strengthen overnight as the secondary low develops and strengthens. 
• Major uncertainties exist regarding Monday.

12z GFS bufkit for Windsor Locks, CT Sunday suggests ample upward vertical motion and more than sufficient relative humidity and ice (not shown) for the generation of moderate-to-heavy snow:

Below are my initial thoughts for Sunday ONLY. This DOES NOT INCLUDE WHAT MAY TRANSPIRE MONDAY:

I will have some additional updates late Friday afternoon.