New England's weather will remain dry and quiet into the start of this weekend as strong ridging continues to hold across the northeast at the upper-levels. On top of this, a rather strong and persistent area of high pressure will remain parked over New England at the surface. This combination will keep the fair and seasonable weather with cold nights going for the region.
As we've mentioned previously this week, the nearly stationary high pressure at the surface will keep conditions very calm, but it will also lead to a subdued warm-up for New England for the rest of this week as it keeps cooler air locked in at the surface. This high pressure will sink to the south of New England on Friday, leading to a light southerly flow. This will keep the warming trend going, but, again, it won't get as mild as it could have been with cooler air at the surface and shallow mixing.
Below: Temperatures around 4,700 feet (850mb) above sea level (1st image) and temperatures around 2,500 feet (925mb) above sea level (2nd image) on Friday morning. You can see a cooler air mass held closer to the ground due to shallow mixing and surface high pressure:
The nearly stationary high pressure system around the region will begin to slide eastward. This will allow for a full pattern change from dry, mainly sunny and seasonable weather to unsettled, mainly cloudy and mild weather. Stronger warm air advection will ensue on Saturday, leading to a more noticeable warming trend heading into early next week. High temperatures will be in the 40s and 50s region-wide by Monday with much warmer overnight lows as a stronger southerly flow takes hold.
As for the unsettled side, a few showers will be possible Saturday afternoon as clouds and moisture increase from the ensuing warm air advection. These afternoon showers will likely be isolated and few and far between. After that, multiple systems will rotate around a trough to our west, leading to periods of precipitation through midweek. It won't be raining the entire stretch from Saturday night to Wednesday, but it will be a damp and cloudy stretch.
Starting off, periods of precipitation will be possible Saturday evening through Sunday as forcing for showers increases. Precipitation will generally move from southwest to northeast across the region during this time. It won't be a steady rain, but showers will be around. Showers are generally looking to be more numerous across western New England. With surface temperatures still around the freezing mark Saturday night into Sunday morning, periods of freezing rain will be possible before a gradual change to plain rain.
As temperatures continue to warm Sunday night, any mixed precipitation across the north should begin to transition to plain rainfall. Sunday night into Monday is when the bulk of rainfall is expected to move through as the frontal system to New England's west (seen on the above graphic) pushes through the region. A widespread soaking rain is currently expected to push through New England from west to east on Monday.
Rainfall amounts currently look to be in the half inch to inch range with western areas and the mountains of New Hampshire and Maine potentially seeing over an inch. Exact rainfall amounts, and where the heaviest rain sets up will need to be worked out over the next couple days. This will combine with snowmelt across areas that have a decent snowpack. Snow depth will be shrinking across New England early next week. Signals for a flooding event are currently low, but trends will be watched as the event draws closer.
Below: Current precipitation forecast through Tuesday morning:
Currently, it looks like Tuesday will see a lull in this unsettled stretch of weather as New England will be between systems. Depending on how the timing shakes out for the frontal system discussed above and an incoming coastal storm (which will be discussed next) will determine exactly when the lull between systems will come, but New Year's Eve may be able to thread the needle for a mainly dry day.
Heading into New Year's Day, another system will likely work through the northeast. This system will likely involve a northern stream low tracking to the north of New England with a coastal low potentially forming near New England or the Mid-Atlantic. The timing of a secondary low development and its track will determine much about the impacts in New England. This does look like a rain event for low elevations, but some mixing and snow will be possible across the higher terrain, depending on the coastal low's track.
Guidance remains split on exactly how this all pans out. A secondary low developing and strengthening near Cape Cod would be favorable for higher precipitation rates and colder air to slip into the system at the higher elevations. A weaker or later development of the coastal low would lead to less precipitation and a lower chance of wintry weather anywhere in New England. With guidance still working out the Sunday to Monday event, this one will be on the back burner for now.
Below: Model roundup (Euro, GFS, CMC & GraphCast) around New Year's Day:
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