Published: 2007-12-17 12:38:31
Updated: 2007-12-17 12:38:31
Posted December 17, 2007
MIKE MOSS SAYS: Stan, Record high temperatures were experienced across the bulk of our viewing area on Monday and Wednesday, as anticipated in weekend forecasts for that period. I do recall forecasting on both Saturday and Sunday that a front would dip into the area from the north on Tuesday, which would make high temperatures cooler than the other two days but difficult to forecast with great confidence, because it wasn't entirely clear how far south the front would progress. As it turned out, the front ended up stalling just north of the Raleigh area and just south of Rocky Mount (in effect, you were near a zone of balance between the northern edge of a warm, relatively moist airmass being pushed toward the north by high pressure south of us, and a cool, dry airmass being pushed south by a high pressure center north of us, and for the better part of the day neither of those airmasses made much progress over the other at the surface). The air on the north side of the front was a shallow layer of much cooler air, and in the boundary zone between the cooler and warmer airmasses, low clouds and fog were prevalent - this isn't too unusual as water vapor associated with the warmer airmass is cooled upon mixing with the cooler airmass and may condense into clouds or fog (in essence a cloud in contact with the ground). On Tuesday, Rocky Mount reported a high temperature of 57 degrees, while Raleigh reached 74 (also a record, though cooler than Monday or Wednesday) and Goldsboro reached 78.
On Monday and Wednesday, the much warmer airmass to the south was dominant and the frontal boundary was pushed up into Virginia - on those days, Rocky Mount reported highs of 78 and 75, while Raleigh reached 81 and 79, with Goldsboro at 79 and 77.
Scenarios involving stalled fronts and shallow, cool, stable layers of air on the north side of a fairly sharp boundary can be fairly common here through the cooler half of the year, and definitely make for some challenging cloud cover and temperature forecasts because they often result in pretty dramatic temperature contrasts across a short horizontal distance, and sometimes a short vertical distance - for example, on Tuesday it is likely that tempertaures about 3,000 feet above your location were in the mid to upper 60s while you experienced mid and upper 50s at the ground. Of course, these same influences can make for tricky wintertime precipitation type forecasts as well, with a variety of frozen, freezing or liquid types possible over a short distance, and sometimes frequent transitions between those types at a given location.