textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Forecast has trended a little warmer and drier today through Tuesday, and freezing rain chances have decreased to less than 20% in the Northern NC Mountains.

KEY MESSAGES

1. Cold air damming becomes established today and continues through Tuesday. Spotty light rain expected across mainly North Carolina, with a small chance of isolated freezing rain along the Escarpment of the Northern Mountains tonight. 2. Cold air damming replaced by much warmer conditions starting Wednesday afternoon, allowing well above normal temperatures to return through the rest of the workweek and upcoming weekend. Daily shower and isolated thunderstorm chances return by Thursday, with the best chances expected over the weekend.

DISCUSSION

Key message 1: Cold air damming becomes established today and continues through Tuesday. Spotty light rain expected across mainly North Carolina, with a small chance of isolated freezing rain along the Escarpment of the Northern Mountains tonight.

A dry-onset cold air damming event is setting up across the area, as a 1037 mb high crosses the Eastern Great Lakes and pushes a backdoor cold front SW thru the forecast area. A few weak waves along the zonally oriented frontal zone will track west to east across the area thru tonight, which will result in periods of moist isentropic lift. The deepest moisture looks to remain largely north of the CWFA, and models seem to be trending drier overall with this CAD event. Less precip will likely result in temps not wet-bulbing down as much, and thus, the temps have trended a little warmer as well. All of these changes have resulted freezing rain being removed from the forecast. Still cannot rule out a few pockets of sub-freezing temps along the Blue Ridge Escarpment in Avery, Caldwell, Burke, McDowell and Mitchell counties. But even if temps do get to freezing, any ice accretions would be on elevated surfaces and very short-lived. Otherwise, it should be cloudy and noticebably cooler today. Temps will 20 to 30 deg colder than yesterday's highs, with a NELY breeze in the Piedmont.

The 00z HRRR develops fairly decent coverage of showers across much of the Piedmont within the wedge, which other guidance does not have. Temps should be too warm for anything but rain with this activity. Lows will be in the 30s in the Northern Mountains to mid to upper 40s in the Upper Savannah Valley.

CAD should linger well into Tuesday, despite the parent high pushing off the East Coast. Isentropic lift will keep plenty of low clouds in place, but moisture depth will be too shallow for anything more than patchy sprinkles and/or drizzle. Highs will rebound slightly due to the weakening CAD, close to normal.

Key message 2: Cold air damming replaced by much warmer conditions starting Wednesday afternoon, allowing well above normal temperatures to return through the rest of the workweek and upcoming weekend. Daily shower and isolated thunderstorm chances return by Thursday, with the best chances expected over the weekend.

Anomalously high thicknesses will be present as anything left of a residual cold pool will quickly be eroded by low-level WAA and daytime mixing, leading to much warmer temperatures by Wednesday. Upper ridging offshore the Southeast Coast will keep the area well above normal through the end of the workweek and upcoming weekend with continued southwesterly moisture advection from the Gulf of America with the surface high setting up shop near Bermuda. As a result, daily PoPs return to the forecast starting Thursday, but likely in the form of WAA showers and isolated thunderstorms, with enhanced diurnal coverage. Wednesday remains mostly dry as that will be the transition day from the CAD setup into the WAA regime as it becomes fully established by Thursday into the upcoming weekend. Well-above normal temperatures starting Wednesday and Thursday with afternoon highs in the 70s. Temperatures climb even higher by Friday into the upcoming weekend with widespread 70s and even lower 80s possible across the Piedmont zones.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Development of MVFR cigs continues to be delayed, but there are some MVFR clouds beginning to develop across the NC Piedmont and eastern SC Piedmont, and these should continue to expand/increase across the terminal forecast area thru the morning hours. With NELY flow, cigs could lift to low-VFR by early aftn. Then, cigs are expected to be MVFR tonight, with IFR potentially at KCLT and KHKY before 12z Tuesday. Cold air damming should weaken, which may allow cigs to lower into IFR range across the area Tuesday morning. Winds will be in typical CAD configuration, with NE winds in the Piedmont and lighter SSE wind at KAVL. Winds are expected to be strongest and gustiest this morning, then gradually weaken thru the day.

Outlook: Cold air damming continues into Tuesday. Rain chances diminish but restrictions will likely linger. VFR is expected to return on Wednesday, while another cold front may bring showers and associated restrictions late Thursday into Friday.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.