[5 PM Sunday] Monday Winter Weather

Good evening!

Forecast certainty has gone up for the event tomorrow, so let’s dive right in. There is still a level of uncertainty, though.

Precipitation Types

Snow, rain, freezing rain.

Timing

Snow begins from south to north from late evening to around midnight tonight. The changeover is quick along the south coast, and then it gradually comes north. By 7 or 8 AM, most of eastern MA/RI/CT is no longer at pure snow. Most of those locations will be at rain; but a few spots will be at freezing rain, and northern MA is still probably all snow at this point. After that, it appears quite possible that cold air will be slow to leave in some of those spots, and freezing rain will develop in most of northern and central Massachusetts into south-central New Hampshire, and should already be at that state in northern Connecticut and adjacent CT River Valley in MA. Most of these locations should see at least a brief period of pure rain before precip leaves around midday. Also included in the mixed precip party is coastal Maine and New Hampshire, but it is probably more of a snow/rain/sleet thing here – but some ice is still within the realm of possibility. Most of NH, VT, and ME plus northwest MA stay all snow for the duration. In any case, precip moves out from the late morning in far southern New England to the evening in northern New England, hitting a midday exit for southern NH and northern MA.

Snowfall

There is a degree of uncertainty here: if cold hangs on a bit, these numbers either achieve the high end of the range or they are a bit too low. If warm air advancement is a bit faster than expected, these numbers either are too high or hit the low end of the range. Models always have trouble with temperatures in these types of situations, so it’s always good to have human input.

snow 5 pm 12 11 16.png

Freezing Rain

As noted, freezing rain won’t affect everyone. But for those it does affect, a trace to five hundredths of an inch is expected.

ice 5 pm 12 11 16.png

Impacts

The worst of the weather will occur during the morning rush hour. As a result, widespread school delays appear to be likely, and closings are more likely than not where there is the heaviest combination of snow and ice (i.e. the 4-6″ zone plus the trace to 0.05″ zone is where closures are most likely to occur – lower certainty on that at the NE MA coast, but I feel confident in it elsewhere). The morning commute is going to be really difficult for almost everyone, but especially in those areas I noted. Take it slow and careful tomorrow morning, and postpone travel if possible. Widespread accidents appear likely.

Uncertainty

If cold hangs on for longer, expect more snow (and if temps aloft warm up, then expect more ice). If warm air advances faster including at the surface, expect more plain rain for a lot of the area.

Have a good evening!

-Nathan

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