Posts

John Homenuk

Seasons coldest air to infiltrate the Northeast this week

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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.

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John Homenuk

Strong cold front will bring Autumn air to Northeast

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A strong cold frontal boundary, currently situated across New York State and New England, will drop southward through the Northeast states Friday evening and early Saturday morning. While a north to south moving cold front may seem somewhat uneventful this time of year, the temperature gradient associated with this particular front is quite impressive.

Moreover, the airmass behind it is quite cold — even for this time of year — with temperatures 10 degrees below average or more, even in parts of New England where seasonal averages are rapidly falling now. The mid to upper 80 degree temperatures located ahead of the front will become a distant memory throughout most of the region by Saturday, when highs will struggle to reach the low 70s, and may not reach 70 in northern suburbs. A northerly breeze will help it feel truly like Autumn.

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Doug Simonian

Tropical downpours likely in Northeast US this weekend

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Other than a few scattered passing thunderstorms on Wednesday, much of the Northeast US has been devoid of rain over the past several weeks. This is about to change, perhaps dramatically so in some spots. On Sunday, a cold front and associated potent shortwave trough with plenty of vorticity will run into a well established Southeast Ridge, and the remnants of Tropical Storm Julia — two great moisture sources. This combination of energy, dynamics, and moisture — as well as the fact that the ridge and the mid-level flow are parallel to the frontal boundary — will lead to the potential for slow-moving tropical downpours, some of which will train over each other and lead to flash flooding.

As we move towards Autumn, atmospheric troughs can deepen and amplify more than during the warmer summer season. This, combined with tropical moisture and dynamics can lead to impressive meteorological results. This particular shortwave trough is digging from the Great Lakes all the way down to the Tennessee Valley, and is even tilting neutrally or negatively on some guidance. This acts to slow down the atmospheric flow even more, leading to a prolonged fetch of moisture, lift, convergence, and thus heavy downpours.

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