Freezing Night in Store Tonight Before Potential Coastal Storm This Weekend

Cool, Canadian high pressure will build into New England behind the cold front, helping to lock in the cooler air through the rest of the work week. It may initially be a bit breezy today as the pressure gradient between the center of the high pressure to our northwest and the departing trough to our east will be rather tight. The high pressure will sink southeastward through this time, gradually reducing winds as the center of the high moves directly over New England Thursday night into Friday.

This high pressure system will likely be directly overhead of New England tonight into Friday morning. This is a rather strong high pressure system that will lead to nearly perfect radiational cooling conditions. Still winds, clear skies and very low dew points will allow temperatures to bottom out into the low 20s north to low 30s south. The first widespread region-wide freeze is expected tonight. Northernmost New England's growing season has officially ended and therefore frost and freeze alerts are no longer issued for northern counties.

After the freezing start, Friday's recovery will be quick, so the sub-freezing temperatures won't last very long for southern and central New England. Afternoon highs will likely bounce back into the upper 50s and 60s. Saturday will be slightly warmer and dry with high pressure remaining in charge. At the same time, a coastal storm system will begin to take shape off Florida's coast along a frontal boundary. This will be the next system to watch for New England.

This system will work up the east coast Saturday and Sunday. Its movement will likely be quick initially, but it will slow down as it reaches the Mid-Atlantic. As of now, the most likely timing for the system to reach toward New England will be later Sunday and Monday. This system will be the first fall nor'easter of the season and may bring heavy rain, winds and the potential for coastal flooding to at least a part of New England. The main question will be how far north it can get with a strong area of high pressure to the north of New England.

As stated before, the high pressure around New England during this time is a rather strong one, and its position will determine what kind of impacts New England sees from the nor'easter. Trends over the past couple days have generally pointed to a more northern track, sending more rain and wind into southern and central New England.

At this point, model guidance has been divided into two camps (similar to what we see for snowstorms). Some point to a northernmost solution while others keep the storm well offshore. At this point, the storm is likely to come close enough to bring rain and wind, the question will be just how much.

Below: A more northerly solution from GFS (1st image) and the southernmost solution from CMC (2nd image):

More solutions paint a picture that will see the system impact southern New England with a potentially sharp cutoff in rainfall moving north in the region. Should this system come close enough to New England, a soaking rainfall later Sunday through Monday will be possible, with 1-2+ inches for southern New England. Exact rainfall totals, and where the heaviest rain sets up remain to be determined, but the best chances for a long-lasting, soaking rain will be across the south coast and eastern Massachusetts.

Below: Current 5-day rainfall outlook (this represents more of a trend and these amounts certainly are not locked in):

The other impact from this system could be the potential winds. A nor'easter off the coast and a rather strong area of high pressure to the north will lead to a tight pressure gradient. This will be supportive of strong wind gusts across the region. These winds would, naturally be strongest at the coast, but the tight gradient would support at least breezy conditions region-wide.

A gusty northeast wind and rough seas will also promote the potential for some coastal flooding. At this time, the coastal flood threat does appear to be closer to the minor side. The CMC's most southerly solution would represent the worst-case scenario for coastal impacts as the storm stalls to the south and allows seas to continue to build after the "king tides".