Clear skies and calm winds opened the door to efficient radiation of heat overnight. Thus Friday morning's low temperatures around Mecklenburg county dropped all the way down to 27 degrees at several sites. After that chilly start local thermometers will top out in the low 50s this afternoon accompanied by light northeasterly winds. Clear skies will be the rule for the first half of the day, with clouds increasing during the late afternoon.
Saturday looks to again start with temperatures in the upper 20s under mostly sunny skies. Northeasterly breezes will continue, eventually ushering in low level clouds thanks to moisture from off the cool Atlantic waters. Highs tomorrow will top out in the upper 40s for another cooler than average December day.
A northeasterly wind direction signals a cold air damming event for the East Coast. These setups occur when high pressure is centered over New England, forcing a low level "wedge" of cold air down the coast east of the Appalachians. This diagram illustrates, with the top panel showing a cross section east of the mountains:
The bottom panel shows the forecast surface map at 7 o'clock Sunday morning, with the light blue arrow drawn along the axis of the wedge. Note the colorful precipitation shading across western Virginia. Mixed wintry precipitation is expected there Sunday morning.
But by the time any moisture from the storm system (red "L") approaching from the west reaches Mecklenburg county on Sunday, the precipitation will all be just rain. High temperatures Sunday afternoon will be near 50 degrees under mostly cloudy skies, with light rain showers likely. That chance of showers will continue Sunday night into the beginning of the work week.
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