There remain a few chances for snow and rain over the next five days for New England, though no large-scale storm systems are in the picture during this time. Amid these precipitation chances will be up and down temperatures that will culminate with the most potent Arctic blast of the season so far early next week.
TONIGHT-FRIDAY MORNING | IMPACT: NONE
The first chance to see at least some flakes will come this evening as a small, weak and subtle disturbance scoots across the region. All aspects of the system are weak and moisture is extremely limited. The system will mainly support an increase in clouds this afternoon and overnight, but there may be just enough forcing to spit out a few flakes at times for a couple hours.
Below: NAM showing potential weather late this evening:
The best chance for minimal accumulation will be across Cape Cod and the Islands due to potential ocean enhancement. A weak surface low may form in the Gulf of Maine, creating a cyclonic flow and offshore snow showers. Some of these snow showers could back into the immediate coast for a time Friday morning. This can be seen as a low probability for an inch of snow over the Gulf of Maine and near the coastline, seen below.
Below: Probability of an inch of snow through Friday morning:
SATURDAY-SUNDAY MORNING | IMPACT: LOW
A frontal system will cross New England this weekend. The system's warm front will push through New England Saturday morning followed by a cold front later Saturday into Sunday morning. A strong southerly low-level jet will develop on Saturday, aiding in a warm-up. Most of New England will rise above freezing with southern and central areas likely pushing into the low to mid 40s. This strong low-level jet will likely create gusts of 25-40mph, with the strongest gusts in the Champlain Valley. It certainly won't be a biting wind as it will advect mild air.
On the precipitation side, a period of showers is likely to develop across western New England Saturday afternoon and push generally eastward through the afternoon and into the evening. Precipitation will tend to be rain showers for southern New England and the northern New England coastal plain while a mix or snow showers will be likely for the northern third of the region.
Both rain and snow showers will be light and likely patchy with very light accumulations of both snow and rain. The precipitation will wind down from west to east through the overnight hours as drier air pushes in behind the system's cold front. The cold front will likely have nearly finished crossing New England by Sunday morning.
Below: Probability of at least an inch of snow from Saturday morning to Sunday morning:
Colder air will begin working into New England behind the cold front, but it may take some time for the cold air to reach the surface across much of New England. This will allow temperatures to reach respectable levels for Sunday. It will be colder across western New England as the cold front naturally crosses soonest.
Below: Euro showing temperature departure from average Sunday afternoon:
SUNDAY AFTERNOON-MONDAY MORNING | IMPACT: LOW TO MODERATE
The cold front will slow down as it reaches New England's coastline for Sunday into Sunday night. A wave of low pressure may quickly develop later Sunday along the slowed front and track northeastward within near New England. Depending on exactly where the system tracks, a quick period of snow will be possible across southern New England and closer to the northern New England coastline.
Where the low tracks will all come down to the timing and location of the cold front and the colder air behind it. If the cold front is more progressive and the push of colder air behind the front is stronger, the system will be pushed offshore. A slower frontal passage would result in a more westerly track, resulting in more by way of a rain/snow mix changing to snow. We're still leaning toward a middle ground, where a period of snow may result in light accumulations over a good portion of southern New England, southern New Hampshire and possibly coastal Maine.
Below: Euro, GFS and CMC recent model runs, each painting an outcome described above:
This kind of setup is known as anafrontal. When most cold fronts cross New England, they advect cooler and drier air into the region, allowing precipitation chances to diminish (which are known at katafronts). When an anafrontal setup occurs, the cold air rapidly pushes against the warmer air ahead of the front, causing the warmer air to rise over the colder air behind the front, resulting in clouds and precipitation behind the front rather than clearing.
The wave of low pressure will aid in creating precipitation on the cold side of the front over New England, given the track is close enough to the coast. These types of setups aren't conducive to a major or powerful storm system. With that said, the most likely outcome with this system will be a broad few inches of snow. The system should be a quick mover, arriving later Sunday and departing by Monday morning, though the exact timing will need to be hammered down when the exact track becomes more clear.
Below: Current probability of impactful winter weather during this time:
ARCTIC BLAST (MONDAY-WEDNESDAY)
The Arctic blast of air coming next week will likely peak (or bottom out) early to mid-week. This blast will likely be deep and widespread across the central and eastern United States. For New England, the lowest temperatures appear poised to come in the Tuesday to Wednesday time frame. These days will likely see high temperatures in the single digits north to teens south.
Overnight lows will be in the single digits, on either side of zero. There will be a chance the coldest hollows of northern New England (mountains, Northeast Kingdom and northern Maine) will drop into the -10s. Wind chills will drop below zero during this time region-wide with minimum values potentially reaching for the -15 to -25° range.
Below: Euro showing potential wind chills Wednesday morning (January 22). This is just a rough estimate and will likely be modified as we draw closer to the blast:
This blast of cold air will be coming mainly thanks to a strong negative Eastern Pacific Oscillation (EPO). When this oscillation is negative, a large ridge typically builds near the Alaskan and western US coasts with a deep trough digging into the central and eastern United States. A strongly negative EPO favors a cross-polar flow from Siberia to move southward into the United States while keeping Alaska very mild (as seen below).
As we get closer to this Arctic blast, this is a good time to remind everyone of changes to cold weather alerts that the National Weather Service made coming into this winter. Wind chill advisories have been replaced with cold weather advisories and wind chill warnings have been replaced with extreme cold warnings. Should alerts be needed next week, these new alerts will be used.
BEYOND
Looking at the long term, a southern stream storm system appears poised to develop around early to mid next week near the Gulf of Mexico. This could bring the south another winter storm next week. Where this storm goes from the south is anyone's guess at this point.
Whether or not it hugs the coast and comes up to the northeast or remains well offshore will likely come down to the timing of the Arctic air. Should the Arctic air mass hang around, it would likely stay offshore later next week, but this is trying to look out too far to get into any kind of detail.
Below: Weather Prediction Center probability of impactful winter weather around midweek next week:
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