Precipitation has arrived in New England as a coastal, southern stream low pressure system approaches from the Mid-Atlantic. Trends yesterday pushed the track of this low farther north. Most guidance has the storm center tracking near Boston. These trends have held this morning. This trend led to an increase in the chances for heavier snow bands across interior northern New England, but did not affect the rain for southern New England and northern New England coastal plain.
ALERTS
Since yesterday evening, winter weather advisories were expanded to include northern Berkshire County, MA; Franklin County, VT; Strafford County, NH; interior Hancock County, ME and interior Washington County, ME. Winter Storm warnings were extended into the Northeast Kingdom of Vermont.
TIMING
Rain and snow will continue to fill in across New England throughout the morning hours. Heading into the early afternoon, steady rain across southern New England and the northern New England coastal plain will be ongoing with snow across the interior. As the system tracks over southern New England this afternoon, colder air will wrap around the backside of the system. There looks to be enough interaction with the northern stream to allow for heavier bands of snow to develop.
Below: HRRR showing potential weather early this afternoon:
The heaviest of the snow bands will likely occur from mid-afternoon through the evening hours for Vermont and New Hampshire. Maine will see these bands from the evening through the first part of the night. Snowfall rates of 1 to 1.5 inches an hour will be possible across the interior, mainly in the mountains. A steady, soaking rain will continue through this time for southern New England.
The rain/snow line will try to collapse closer to the coast later in the afternoon and evening across northern New England, but any accumulations near the coast look to be very light to non-existent. Still, how close the frozen precipitation can get back to the coast will be something to watch later today.
Below: HRRR showing potential weather late this afternoon:
As we've been saying for a while, this will be a progressive storm that will not linger around for too long. Precipitation will shut down from west to east starting Thursday evening and continue through Thursday night, with eastern Maine seeing steadier precipitation likely end late Thursday night into early Friday morning.
Below: HRRR showing potential weather this evening (1st image) and around midnight tonight (2nd image):
SNOWFALL
As one would expect in an earlier season storm, snowfall will be terrain based. The jackpot zone will likely be over the White and Maine mountains, where over a half foot may fall. Here, the storm will start and end as snowfall. Amounts will drop heading south with the foothills and Lakes Region likely seeing 3-6 inches. The Green Mountains are interesting, they will likely see some amounts similar to the White Mountains, but not as widespread. The mountain valleys will see less than the slopes across northern New England.
Amounts will really drop off heading to the coast and southern New England. The Berkshires may be able to pick up a couple inches while the Worcester Hills will see little if anything. The northern New England coastal plain will see little if any accumulation. Lower elevations across southern New England will see all rain. The best chance for notable accumulations will be at or above 1,000 feet. The Champlain Valley will be similar to southern New England with more mixing and rainfall likely over snowfall.
We mentioned in previous days that if the storm were to take a more northerly route, the storm would be stronger (due to more interaction with the northern stream system in Canada) and lead to heavier snow banding. These northerly trends came true yesterday with the storm track shifting from near Cape Cod to near Boston.
This led to a large expansion of our 5-8 inch zone. Some guidance is showing up to a foot of snow, but we're hesitant to buy into amounts that high due to the fact that this won’t be a very deep or powerful storm and it will be moving along at a decent clip. There's limited blocking with this system, leading to a less amplified and more progressive storm. There is a distinct lack of colder air ahead of the storm. There is also no strong area of high pressure to the north of New England to filter colder air into the system as it occurs.
The main way heavier snowfall rates will develop is through some strengthening of the system with limited interaction with the northern stream. That interaction is the only reason amounts have increased to where they are now. Just how much the storm can strengthen will determine if higher snow totals (8+ inches) can develop or not. Interior Maine has the best chance for higher totals as the storm will have had the most time to strengthen as it passes. There will likely be some spots that see double digits in Maine.
Below: Weather Prediction Center probability of at least 8 inches of snow:
The heaviest snowfall rates will likely occur from mid-afternoon through the first part of Thursday night. This means snow will likely be slow to start, but it should ramp up as the day goes on. When snowfall rates ramp up, it will likely happen rather quickly. Snowfall rates of 1 to 1.5 or more inches an hour are likely across the higher terrain of northern New England.
BUST POTENTIAL
As we've said all along, bust potential is high with this one. The main way the storm could bust will be if the storm doesn't strengthen much. Dynamic cooling will be needed to produce heavy snowfall rates. This process won't occur if the storm can't deepen. The fast-moving nature of the system will make it difficult for the storm to gain too much strength. Marginal temperature profiles will make the rain/snow line finicky. Areas most likely to underachieve will be the Lakes Regions of New Hampshire and Maine.
RAIN
This will likely be another decent soaking for southern New England and the coastal plain of northern New England. A widespread half an inch to an inch of rain is likely across these areas. Thanksgiving will be a washout for areas that see rain for the entirety of the event. Lesser rainfall amounts will naturally be seen where more snow falls farther north.
Much of New England does remain in a drought, with most of southern New England in either a severe or extreme drought even after last week's rain as rainfall deficits from the fall are several inches. While the timing of the storm coming on Thanksgiving day isn't ideal, the precipitation it brings is needed.
WIND
Since the storm won’t be all that deep or powerful, winds will be limited. Gusts of 25-35mph will be possible, which is below impactful levels. It will create a wind-driven rain and with highs in the 30s to low 40s, it will add to the cold, raw feel out there.
BEYOND THIS STORM
The prolonged chill coming after this storm remains on track with the entire first week of December set to feel like winter. Widespread highs in the 20s north and 30s south with lows in the teens are likely. This will last for much of next week. With the colder air will come quieter times with minimal precipitation in the forecast for the next week (after this storm, of course).
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