Radiational Cooling

By Justin Culligan

July 22, 2010 Updated Jan 20, 2009 at 7:14 AM EDT

Several mornings within the last week have featured exceptionally cold temperatures in some parts of the Twin Tiers. Minimum temperatures plunged into the teens and even the 20s below zero in localized areas last Friday morning, last Saturday morning, and most recently this morning. If you pay close attention to the regional temperature map I use during our morning broadcast, you've probably noticed that some parts of the area tend to be much colder than others. So why do these certain areas tend to run much colder than other places on a fairly consistent basis?

There are two primary reasons for these rather unique temperature anomalies: radiational cooling and topography. Radiational cooling occurs when relative warmth that has built up at the Earth's surface during the day suddenly radiates skyward in the absence of cloud cover after sunset. Temperatures initially cool most rapidly on the elevated hillsides across the region...but as the air grows colder and becomes more dense, it eventually sinks into the valleys as a result of gravity. The cold air will ultimately settle into the lowest spot it can find...therefore the deepest valley locations often report the coldest temperatures on clear and calm mornings. In some extreme instances, temperatures in those deepest valley locations can run 20-25 degrees colder than surrounding areas! This is why places like Smithville Flats, Jenksville, Speedsville, and Weltonville can report temperatures as cold as -20 or -25 while the Binghamton Airport is just barely below 0.

Here are some of the coldest temperatures observed in our viewing area within the last week:

-27F (Jenksville, Saturday 1/17)
-26F (Speedsville, Friday 1/16)
-26F (Weltonville, Friday 1/16)
-22F (Roscoe, Saturday 1/17)
-20F (Hancock, Saturday 1/17)
-20F (Newark Valley, Friday 1/16)

The coldest temperature observed at the Binghamton Airport during this period was -6F on Saturday 1/17.

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