Undercast!

If Connecticut had 3 or 4-thousand foot mountains we would have been treated to beautiful scenes like these from Killington, VT and Stowe, VT this past week.

Courtesy: Killington

Courtesy: Stowe Mountain Resort

When moisture is trapped in the low levels of the atmosphere you can get these dramatic views of an undercast. Just like overcast except under!

Frequently these areas of low level moisture get trapped horizontally on one side of a mountain and vertically by a temperature inversion. Inversions are locations in the atmosphere where temperatures increase with height (they typically decrease with height). The phenomenon isn’t rare – it happens almost every day – but when there’s enough moisture below the inversion you get clouds that are trapped.

Here’s a model forecast sounding from Springfield, VT this morning (not far from where the first picture was taken).

While temperatures near the ground are around 2ºC temperatures at 2200 ft are near 6.5ºC! That’s a difference of nearly 10ºF. Coupled that with adequate low level moisture (notice the red and green line, or temperature and dew point are close together) you get clouds.

Enjoy the undercast up north – hopefully the overcast in Connecticut breaks soon!

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5 thoughts on “Undercast!

  1. Pingback: PM Update: Clouds thicken late tonight ahead of Tuesday showers; New England undercast - The Washington Post

  2. Great info! I’m a hobby landscape photographer, and I love inversions. What is the source of the graphic near the bottom of the post that shows the temperature and dew point for different elevations? Please let me know, I’d love to find forecasts like that for my local location in Oregon. I’ve searched weather and aviation weather sites, and haven’t found anything yet.

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