textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The severe thunderstorm threat has ended with the earlier line of storms moving east of the area. The Severe Thunderstorm Watch was cancelled just before 11 AM.

KEY MESSAGES

1. The line of thunderstorms has moved east of the area late this morning, ending the severe weather threat. 2. Precipitation will change to snow across the higher mountain elevations this afternoon with period of northwest flow snow through this evening. Gusty winds will develop behind the cold front this afternoon and continue through Tuesday. 3. Cold air mass lingers through Wednesday night, with freezing temperatures returning Tuesday night and possibly again Wednesday night. Warmer temperatures return Thursday into the weekend, with mostly dry conditions continuing.

DISCUSSION

Key message 1: The line of thunderstorms has moved east of the area late this morning, ending the severe weather threat.

Severe Thunderstorm Watch 64 was cancelled just before it was set to expire at 11 AM. Trailing stratiform rain will continue across most of the area before gradually exiting from southwest to northeast between 3 PM and 6 PM. The one exception will be the higher elevations in the Smokies where northwest flow will advect colder air into the area and lead to upslope snow this afternoon. More on the mountain snow and gusty winds in the second key message.

Key message 2: Precipitation will change to snow across the higher mountain elevations this afternoon with period of northwest flow snow through this evening. Gusty winds will develop behind the cold front this afternoon and continue through Tuesday.

Strong cold advection behind the front will bring a precipitation changeover to snow across the higher mountain elevations during the afternoon. These northwest flow snow showers will continue into the evening before tapering off after midnight. The latest guidance has increased snowfall totals with amounts of 2 to 6 inches above 3500 feet in the higher elevations along the TN border. Amounts around 8 inches are possible in the highest elevations of the Smokies. The guidance has increased the probability of these amounts high enough to increase confidence that a Winter Weather Advisory is needed for elevations above 3500 feet for the counties along the TN border. Some valley locations will see a dusting to perhaps an inch. Winds turn to the NW and become very gusty behind the front. High elevations of the NC mountains will see gusts as high as 55 mph, so the Wind Advisory still looks well placed. That said, gusts to 35 mph and possibly 40 mph will be possible for the lower mountain elevations, and some locations outside of the mountains. The gusty winds linger into Tuesday, but not as strong as today's winds. The cold air mass will bring lows 10 to 20 degrees below normal. Highs Tuesday 15 to 20 degrees below normal.

Key message 3: Cold air mass lingers through Wednesday night, with freezing temperatures returning Tuesday night and possibly again Wednesday night. Warmer temperatures return Thursday into the weekend, with mostly dry conditions continuing.

Upper troughing remains over the region through Friday before pushing east over the weekend. At the surface, cool and dry high pressure continues building over the East Coast through Wednesday, bringing much cooler and well below normal temperatures. Lows Tuesday night are likely to fall below freezing again, with the NBM showing a 100% chance of temperatures falling below 33 degrees across nearly the entire GSP CWA. Lows Wednesday night could fall below freezing again, but the NBM shows lower probabilities (~40% to 70%) of T<33, mainly for locations east of the mountains. Thus, confidence on freezing temperatures east of the mountains Wednesday night is lower compared to Tuesday night. Regardless of lows falling below freezing again Wednesday night, sensitive plants that have already bloomed from the recent abnormally warm weather will remain particularly vulnerable to these cold temperatures each night.

The southern periphery of the surface ridge will extend across the Southeast through Thursday night before getting pinched off Friday into Friday night as a cold front sinks southward across the Great Lakes and Ohio Valley. The area of high pressure will then center itself over Florida/the eastern Gulf over the weekend while a mostly dry and weak cold front tracks across Georgia and the Carolinas late Saturday. This pattern will allow much warmer, well above normal temperatures to return Friday into the weekend. Thursday will be warmer as well, but will most locations will see highs end up near to just below normal. Mostly dry conditions should linger for most areas as well.

AVIATION /15Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Line of convection moving into the area at this time. Have TEMPOs for TSRA and strong variable winds with MVFR restriction for this. Once the line moves through, MVFR SHRA continues into the afternoon with gusty WSW winds. When the cold front moves through later in the afternoon, skies clear out and winds turn W to NW and remain gusty. Winds drop off overnight. KAVL sees S wind and LLWS, turning NW behind the line with winds becoming very gusty for the afternoon into the evening. Gusts remain all night with low VFR and possibly MVFR cigs. There is also a low chance of flurries there, but too low for the TAF at this time.

Outlook: Gusts subside on Tuesday and come to an end by Wednesday morning, with VFR through Friday

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Winter Weather Advisory until 3 AM EDT Tuesday for NCZ033- 048>052-058. Wind Advisory from 4 PM this afternoon to 5 AM EDT Tuesday for NCZ033-048>053-058-059-063-064. SC...None.