Seasons coldest air to infiltrate the Northeast this week

The coldest air of Autumn 2016 to date will surge into the Northeast United States this week, as a deepening trough passes through the Great Lakes and Southeast Canada. After an initial surge of cold air earlier this weekend, secondary surges on the heels of multiple disturbances will arrive this week, and by midweek overnight low temperatures could reach 15 to 20 degrees below normal in some locations.

The airmass will settle in from Tuesday through Thursday before the approach of another storm system. Overnight lows on both nights will be very cold in the Northeast, especially in the interior. For agricultural interests, Freeze Watches have been issued as early as Tuesday Night– as a hard freeze may occur in some locations that have not experienced it yet this year.

GFS model showing a trough over the Northeast US late this week leading to cold temperatures in the Northeast US.

GEFS ensemble showing a trough over the Northeast US late this week leading to cold temperatures in the Northeast US.

The cold airmass will “peak” per se, during the middle of the week. Ideal radiational cooling is likely to occur on both Tuesday and Wednesday mornings as a cold airmass settles overhead. It will be, all things considered, the first “true” cold airmass of the season with arctic origins.

The airmass is being driven by the aforementioned deep trough, one which actually began interacting with the Northeast US this past weekend and will continue spinning nearby over the next few days. The cold northwesterly flow will keep cold air in place until Thursday.

While not an overly anomalous feature for this time of year, the trough spinning near the Northeast US is indicative of an overall pattern adjustment which is occurring in the Northern Hemisphere. The ridiculously progressive (and generally warm) pattern which had settled into the area for the past several weeks is finally in a transition out, as wavelengths increase and major changes occur in the higher latitudes (more on the later).

GFS model showing frozen precipitation at the start of a storm system from Thursday Night into Friday, mainly across the interior and higher elevations.

GFS model showing frozen precipitation at the start of a storm system from Thursday Night into Friday, mainly across the interior and higher elevations.

Notably, as the next system approaches from Thursday Night into Friday, moisture may surge into this cold airmass slightly ahead of warming which will be occurring throughout the atmosphere upon the systems approach. Forecast models have suggested the potential for some frozen precipitation, especially across the interior of New England.

While widespread accumulations of snow are not likely, it appears plausible that the atmosphere could briefly support light to moderate frozen precipitation for a period of time across the interior. Precipitation should change to rain rather quickly as warm air advection surges into the Northeast, with a period of heavy rain for most interests early on Friday morning.