Neat Weather Tidbit About Yesterday’s Low Cloud Dam

Hello everyone!

I tweeted yesterday about a neat weather phenomenon I saw on the visible satellite imagery yesterday afternoon featuring a low cloud dam built by the mountains.

Here is the loop full size:

Visible Satellite Loop Yesterday Courtesy COD Sat/Rad page
Visible Satellite Loop Yesterday Courtesy COD Sat/Rad page

As you can see, areas NW of the mountains saw a dreary day due to low level moisture causing low clouds and fog depending on the elevation. Areas SE of the mountains though saw a stunning cloudless day. Why such a sharp contrast?

Moisture was limited to the very low levels of the atmosphere and when the moisture encountered the mountains, its instinct was to rise. It was able to do this somewhat but it was also limited in this endeavor due to a sharp low level inversion which put a strong cap on the ability of air to rise up and over the mountains. The morning weather balloon data from Gray showed this well.

12Z Weather Balloon Data From Gray Showing The Low Level Inversion
12Z Weather Balloon Data From Gray Showing The Low Level Inversion

When the moisture found the mountains, it wanted to rise but couldn’t due to the inversion so as a result, most of the moisture was left stuck in place resulting in a dreary day NW of the mountains and a lovely day SE since the mountains blocked the moisture.

Here is a super awesome timelapse from the summit of Mt Washington showing the moisture trying to pass over the White mountains over in NH. Notice how the clouds are barely able to rise over the passes and how the inversion immediately shunts them down into the SE facing valleys where they sink and warm, thus dissipating and creating beautiful weather for most of ME and NH.

Even during times of relative quiet, New England weather never fails to impress!

Look up tonight to have a shot at seeing the northern lights as a moderately strong geomagnetic storm is ongoing at the moment. Best chance is in northern areas and everyone should look to the northern horizon for the best chance to catch a glimpse. While some clouds are likely to obscure viewing in NW areas, most of the area should have mainly clear skies.

-Jack

6 thoughts on “Neat Weather Tidbit About Yesterday’s Low Cloud Dam”

  1. Jack, just loved the video from Mt.Washington! Really different! It’s always great to learn something new😋

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