An expansive ridge over the central United States and Canada will keep New England firmly embedded under a trough for the rest of this week. This will keep a cold pool centered over New England, which will allow for some sustained fall temperatures and a bit of unsettled weather. The first frosts of the season are expected across portions of northern New England throughout this week.
Below: 500mb anomaly map showing the expansive ridge over the central part of the continent with a cold pool over New England:
High temperatures for most of this week in New England will be in the 50s to low 60s. Overnight lows will drop into the low to mid 30s across much of the northern tier. Central and southern New England will drop into the upper 30s to mid 40s tonight. Frost advisories have been posted across portions of Vermont, New Hampshire and Maine. Far northern areas (and much of Maine) do not have a frost advisory as the frost/freeze alert program ended on October 1st (or earlier in northern Maine), marking an end to the growing season.
The coolest day this week will likely be on Thursday as a subtle disturbance rotates around an upper-level low to the northeast of New England, dragging a surface cold front across the region Wednesday into Wednesday night. Highs Thursday afternoon will likely struggle to get to 60° across all of New England. Much of the northern tier may struggle to reach 50°. Morning lows will likely see another round of widespread 30s. On top of the chilly temperatures, a breeze will keep the day raw feeling.
That upper-level low was responsible for Monday's rain and has since been cut off. This supports broad-cyclonic flow across the region, allowing for showers to pinwheel into New England. The highest chance for scattered showers will come on Wednesday, particularly in the afternoon and evening, as that disturbance pinwheels around the upper-level low.
Showers will be far more likely across northern New England, with much more isolated activity dropping into southern New England. With that said, another quick disturbance may deliver a few showers to southern New England early Wednesday morning, well before sunrise. The takeaway is that the weather will be somewhat unsettled, but overall quiet and dry most of the time.
Below: GFS showing the potential for scattered showers Wednesday afternoon and evening:
With the cold pool aloft, some of the higher terrain of the Green and White Mountains (mainly above 2,500 feet) could see some snow showers over rain showers during this time. The highest chance for this remains over the Adirondacks and New Hampshire's Presidential Range, where minor accumulations are possible.
After another chilly morning on Friday (Thursday night May end up as the coolest of the week), temperatures will begin a brief warming trend heading into the weekend. This will come as the upper-level low slowly begins to push away from New England. Surface high pressure will build in, allowing for more mild temperatures on Saturday.
Below: 500mb anomaly showing the cold pool pushing to the east of New England Friday evening:
Any warm-up for Saturday will be short lived as general troughing will remain in place for New England. An upper low may develop Saturday morning, bringing a chance for showers across the northern tier of New England during that time. Whether this system drops far enough south to bring northern areas precipitation remains uncertain.
Below: Weather map for Saturday (October 12), showing the system to the north:
Another system will likely move through later in the weekend and into early next week, bringing a quick return to cooler temperatures and more chances for some showers. Timing of this system is still in the works nearly a week out, but it looks like late Sunday into Monday will be the better chance for another period of some unsettled weather.
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