1-17-2019 Evening

Good evening! First large update about the snowfall for Saturday night and Sunday. I probably won’t update this until mid-morning tomorrow, but I wanted to get this out to have something for the morning rush viewers tomorrow.

Like in the past, I’ll be going component by component with this.

Timing and Precipitation Type
Snow begins during the 7-9 PM timeframe tomorrow evening. This could pose a few travel issues, but the serious problems don’t begin until later in the evening. Expect the heaviest snowfall to start after 10 or 11 PM. Heavy snow continues until mid-morning, when mixing with sleet will likely begin. A mix of snow and sleet – along with perhaps a light trace of freezing rain, though freezing rain is more likely to our south – continues until late afternoon, when all snow is once again likely for an additional light accumulation before precipitation ends during the evening.

Uncertainty
The exact time of mixing beginning may result in some changes to the snowfall amount. I still think we will get walloped during the overnight and early morning regardless, but it could just add even more to the final number if colder air holds serve for a little while longer aloft. Also, as of 11 PM today, a few key weather models are showing a southward shift on the northernmost extent of the warmer air aloft, which means that there is some potential to have notably less mixing than expected. However, more clarity will be available on this subject by the morning tomorrow, at which I will do a full update.

Snowfall Amounts
DISCLAIMER – The amounts below are subject to change!
I am expecting a widespread 12-20 inches of snow in northern Massachusetts, Vermont, New Hampshire, and Maine; this includes Dracut, as I feel that even if mixing is significant, we are in for enough snowfall – with high enough snowfall ratios, as cold air predominates overnight in this setup – to cross the one foot marker. I would not be surprised to see some spots approach 2 feet, most likely in central and southwest New Hampshire. That said, the location of the 12″ line could waffle a bit. Most of the accumulation in this zone is from snowfall, with a little bit of it coming from sleet in southern sections of this area.

To the south is where this forecast gets a lot trickier, as there will likely be a somewhat sharp gradient between nearly a foot of snow and a few inches. I’m currently going with 6-12 inches of snow for most of the Connecticut River valley, the Worcester area, MetroWest, Boston, much of the North Shore, and a few of Boston’s southern suburbs. Sleet will be a bigger problem here, and freezing rain is a serious concern for large parts of this zone (especially south).

The 3-6″ zone is the lowest confidence zone, and this covers northern sections of southeast Massachusetts, northern Rhode Island, and much of northern and central Connecticut. This is also the high danger zone when it comes to freezing rain.

Further south, up to 3″ can be expected as freezing rain, rain, and sleet will be much more predominant in the south coast area after the initial snowfall, which will be much shorter.

2018-11-19 2245 snow.png

In the freezing rain department, I’m expecting this to be a bigger problem south of the Mass Pike, but a trace icing is possible here nonetheless. This event could pose some significant icing issues in southernmost New England.

2018-11-19 2245 ZR.png

More in the morning!
-Nathan

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