WRAL WeatherCenter Blog

Hi, I talked to a friend on the NC coast and she said it's sunny and 70 degrees. Here, 5 miles north of Hillsborough, it's 41 degrees and SLEETING! Why such extreme differences in temperature just 4 hours away? Is it due to an extremely cold concentrated air mass in the upper atmosphere just over the northern piedmont?

Posted October 28, 2008

MIKE MOSS SAYS:       Paulette,     You saw the effects of a rather strong and sharply defined cold front that was sweeping east across the state at a pretty good clip yesterday, along with the effects of some dry air mixing into a layer or two of moisture above and behind the surface front - there was also some impact from strong jet stream winds providing an enhancement to upward motion just to the west of the surface front. All of that led to a a sharp east to west temperature and humidity contrast, while rapid evaporation of light precipitation in some of the dry layers a few thousand feet up led to enough additional cooling to form some ice pellets that were able to reach the ground in spots despite relatively warm surface temperatures (in terms of frozen precipitation). The kind of temperature contrast between the Piedmont and the Coast that we saw yesterday isn't especially uncommon during the cooler half of the year, and you're likely to see a few more examples like that between now and spring when cold fronts cross the region, especially with fronts that develop a trailing band of clouds and precipitation. It will also occur at times with a looping warm front that leaves the southwestern mountains of our state and the eastern coastal plain much warmer than the foothills, Sandhills, Piedmont and western Coastal Plain as the front slowly drifts northward during a pattern called "cold air damming."


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