UPDATED 6:30pm | Evening updates are in bold
An area of low pressure will move through the Ohio Valley on Sunday morning. This will form a secondary, coastal low that will move to New England's south. This secondary low will gain strength as the energy from the initial low is transferred to it. This coastal storm will pass to New England's south Sunday afternoon through Monday morning.
This will bring southern and central New England accumulating snow. The storm continues to look like it will track near the 40/70 benchmark, which in late January would typically mean big snow for much of New England, but a distinct lack of cold air will likely hold some areas back when it comes to snow totals. This will allow a rain or mix at the start in portions of the region.
ALERTS
TIMING
Precipitation will likely break out across Connecticut by mid-morning. The shield of rain and snow will spread generally northeastward through the morning until it reaches southern Vermont and New Hampshire. The initial burst of precipitation may be snow before changing to a rain/snow mix across southern New England by mid-morning.
Areas that will have the best chance to see mostly snow by the early afternoon will be the higher elevations of southern New England. (Worcester Hills, Berkshires, southern Green Mountains and Monadnocks). With temperatures right around, or just above freezing, some areas may go back and forth between rain and snow with some freezing rain and icing possible.
Expected weather early afternoon Sunday:
Through the afternoon and into the beginning of the evening, precipitation will likely have overspread much of New England minus Maine. By the evening hours, rain, or a rain/snow mix, may still be ongoing across the Merrimack River Valley, Connecticut River Valley and eastern Massachusetts while the Worcester Hills and Berkshires see mostly snow. Most of northern New England will likely have switched to all snow by the evening. The major question that remains will be just how quickly can the colder air arrive in southern New England to switch the rain and mixing over to snow.
Expected weather Sunday evening:
Overall, it looks like the daylight hours on Sunday will see minimal accumulations and impact. The storm will continue to strengthen and cool as it makes its closest pass to New England, likely Monday morning. The overnight hours will be when the precipitation will be at its strongest. The rain/snow line will definitely start collapsing southward by the overnight.
The rain/snow mix will transition to snow generally from northwest to southeast (and from higher elevations to lower elevations). The rain/snow line likely won't make it to Boston until late at night Sunday night into early Monday morning.
Expected weather overnight Sunday to Monday:
By Monday Morning, all but the South Shore and Cape Cod will likely have transitioned to snow. Snowfall rates will also likely begin to gradually wind down. The bulk of the storm will be Sunday evening through about mid-morning Monday. Lighter snow snow showers will likely continue to linger through Monday afternoon.
Expected weather around sunrise Monday:
SNOWFALL
This system seems to be behaving more like a spring-time snowstorm rather than one in the heart of winter. That is to say elevation will likely play a major role in snowfall amounts, especially for southern New England. With that said, confidence is highest in the snowfall amounts on the map below in western and central Massachusetts and south-central New Hampshire.
Overall, our snowfall map hasn't changed too much from this morning. With uncertainties regarding mixed precipitation, there's still wiggle room for snowfall amounts to change, which is why winter storm watches remain in effect for much of central New England instead of being upgraded or downgraded.
As stated previously, confidence is highest in the Worcester Hills, Berkshires, southern Greens and Monadnocks. These areas will see snowfall without mixing the longest. Still, temperatures at or just above freezing may make it difficult for the snow to stick initially. Despite this, snowfall rates of 1 to 1.5 inches an hour will be possible for several hours in these areas.
The rest of southern New England and the New Hampshire seacoast will have trouble accumulating snow for a while thanks to mixing, icing and the snow consistency, which will be heavy and wet. This type of snow doesn't pile up quickly. This will keep amounts across the river valleys and coastal plain lower.
Heading closer to the coast in Massachusetts, particularly Boston and point south will only see a couple inches as the transition to all snow will take most of the storm to complete. These areas will likely still be mixing or raining during the heaviest precipitation. The further south and east you are in New England, the less snow will fall.
This will be a central New England storm with lighter snowfall intensity in northern areas and mild air and mixing in southern areas. Northern Massachusetts, southern Vermont and southern New Hampshire are in the prime spot for the most snow.
The snow itself will be of the wetter and heavier variety for southern New England. This is the snow that clings to everything. When you start getting into the 6-10 inch range with this kind of snow, some power disruption will be possible as some branches may begin to buckle under the weight of the snow. Further north, the snow will not be quite as heavy.
The main bust potential with this storm comes from the fact that models have been trending toward the upper level features phasing together too far to the east of New England to have a significant impact. This is often a factor in storms that bust and this storm will be no different. Another issue is that wet, heavy snow compresses as it accumulates, making it more difficult to pile up.
FREEZING RAIN
The overall trends have been for slightly less snow in southern New England and more mixing. The setup may be primed for a period of freezing rain and icing. The period to watch for some freezing rain would be late Sunday morning through Sunday evening. A dry slot may try to work into southern New England at this time. This would support freezing drizzle. Icing should be fairly light and a minimal impact.
Probability of a glaze of ice by Monday morning:
WIND
The storm will be strengthening as it passes south of New England which will support some gusty winds. The storm will strengthen rapidly, so winds are not expected to reach damaging levels. Still, gusts of 25-35mph will be possible across the interior with gusts 35-50mph along the coast. These gusts in the interior will only put more strain on weighed down branches.
