textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The forecast remains on track.

KEY MESSAGES

1. A cold air mass spreads over the region tonight. A Cold Weather Advisory has been issued for a portion of the mountains late this evening through Tuesday morning. 2. Elevated fire conditions today and Tuesday with Relative Humidity values dropping at or below 25% during the afternoon both days, mainly outside of the mountains. 3. A weak cold front may cross the area Thursday with a slight chance for precipitation. Guidance hints at another system crossing the area next weekend but impacts are highly uncertain.

DISCUSSION

Key message 1: A cold air mass spreads over the region tonight. A Cold Weather Advisory has been issued for a portion of the mountains late this evening through Tuesday morning.

Deep cyclonic flow aloft and a 1035+mb Canadian surface high spewing into the region from the west will allow for cold and very dry air to settle across the CWFA. The surface high will move across the central CONUS today and settle over the Mid/Lower MS Valley into the TN Valley by daybreak Tuesday. With lingering gusts tonight from strong and continuous CAA, expect overnight lows to be 10-15+ degrees below normal across the mountains with sub-zero wind chills at the highest peaks and single digits across the rest of the mountains. As a result, a Cold Wind Advisory has been in issued for Avery County and above 3500' in Mitchell and Yancey Counties for late this evening through Noon Tuesday. Overnight lows will run 5-10 degrees below normal for locations outside of the mountains. Surface high sets up shop across the CWFA for Tuesday, which will lead to mostly sunny skies with temperatures remaining 5-10 degrees below normal in the mountains and up to 5 degrees below normal outside of the mountains.

Key message 2: Elevated fire conditions today and Tuesday with Relative Humidity values dropping at or below 25% during the afternoon both days, mainly outside of the mountains.

With the very dry airmass in place and dewpoints tanking into the teens and single digits for Monday will allow for RH values to drop below 30% to go along with low-end gusts during peak heating as low-level mixing deepens. Fuel moisture will be relatively high with previous precipitation, so a Fire Danger Statement is not needed at this time. Very dry airmass fully settles in on Tuesday as dewpoints drop even lower starting tonight compared to this afternoon. RH Values tank below 20% for a good portion of the Piedmont zones and fuel moisture levels should be lower with a full day of drying from today. The limiting factor will be the lack of winds as the surface high settles over the area Tuesday and helps to relax the pressure gradient. Afternoon highs will be a few ticks below normal both today and Tuesday outside of the mountains.

Key message 3: A weak cold front may cross the area Thursday with a slight chance for precipitation. Guidance hints at another system crossing the area next weekend but impacts are highly uncertain.

By the end of the week, an extremely strong upper low situated over Canada, flattens the trough out over the southeast. Guidance continues to trend drier as the supposed cold front at this time looks to scrape by the northern part of the CWA. This frontal boundary ushers in another round of high pressure across the central CONUS and eventually eastward. Previous guidance hinted at potential precipitation along this boundary, but current models are backing off. At this time, Wednesday night into Thursday has a slight chance (15-30%) for precip, with the higher chances across the mountains. QPF response looks almost barren as well, so even if anything develops, it would be a quick shot. IF cold air makes it, this could be a brief wintry mix. Modeled soundings show a very weak warm nose Wednesday night, but it quickly diminishes, allowing for any icing to be disrupted. At this time, looks to be a very quick burst of snow at the TN/NC border IF anything can develop.

As for the even further out potential system for the weekend, model guidance keeps the high pressure parked over the central part of the country and eventually makes its way into the area. There is much discrepancy and uncertainty if the frontal boundary is able to make anything of the weak moisture return. Friday and Saturday could see a mix of precip but again, its too far out. There is a possibility for a wintry mix as the transition zone and colder air move in. A few of the individual models show a signal for snow, but there is still much uncertainty. Any shift north or south of the potential boundary could be the difference in rain, snow, or nothing at all. And as this location has seen again and again, it's all a matter of whether or not the cold air can even make it in time. Will continue to monitor as this system is going to change this far out.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions will prevail through the forecast period. Clear skies across the area as much drier air filters in. Light southwesterly winds through daybreak, will become more westerly during the daytime period at 6-12 kts. Increasing high clouds are expected tonight as winds toggle more west to northwesterly at 3-6 kts. KAVL expected to maintain a northwesterly component through the period. A few low-end gusts can't be ruled out during the afternoon hours at all TAF sites.

Outlook: Dry high pressure will settle over the region through midweek, keeping VFR conditions across the region. A cold front may bring a chance of some light precip, mainly to the mountains Wednesday night into Thursday.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Cold Weather Advisory from 9 PM this evening to noon EST Tuesday for NCZ033-049-050. SC...None.