textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

A Frost Advisory was issued for Sunday night for portions of the NC mountains which have not already been "turned off" due to a prior freeze.

Updated the aviation discussion for the recent 18Z TAF issuance.

KEY MESSAGES

1. Patchy frost is expected to develop tonight across much of the NC mountains and some portions of the NC Foothills. A Frost Advisory has been issued for those mountain zones that have not already been turned off for the season following a prior freeze. 2. Benign weather still looks to continue early through next weekend. The next chance for rain may arrive by next Sunday, but confidence is limited.

DISCUSSION

Key message 1: Patchy frost is expected to develop tonight across much of the NC mountains and some portions of the NC Foothills. A Frost Advisory has been issued for those mountain zones that have not already been turned off for the season following a prior freeze.

A stout z500 ridge now extends from the Gulf Coast all the way north to the Great Lakes, with a 1035mb surface high centered over the NJ coast continuing to support weak cold-air damming across the western Carolinas. Below-normal temperatures and light winds overnight tonight are expected to develop as a result of excellent radiative cooling conditions, and this should contribute to patchy frost developing across the NC mountains, and even some parts of the NC foothills along the I-40 corridor. Although coverage is expected to be limited based on the current temperature forecast, there would appear to be some potential for temperatures to drop a couple degrees lower-than-forecast owing to an excessively-dry atmospheric column. As a result, a Frost Advisory has been issued for those zones across the NC mountains that have not already been "turned off" for the season based on a prior freeze...which includes most of the mountains south of I-26, as well as Burke and Caldwell Counties, along the I-40 corridor.

Key message 2: Benign weather still looks to continue early through next weekend. The next chance for rain may arrive by next Sunday, but confidence is limited.

The general consensus among model ensembles remains for upper ridging to remain in place through at least Tuesday or Wednesday, before gradually deamplifying through the end of the week. The surface pattern will similarly remain stagnant, with the present sfc high gradually modifying and breaking down through Tuesday, before being reinforced by a new cP air mass on Tuesday night or early Wednesday.

As for fire concerns, the dominant solution in long-range ensembles now features any weak reinforcing frontal boundary sliding through the area Tuesday night. As a consequence, it's looking more and more likely that any stronger low-level winds which might contribute to low-end fire danger issues will be unable to mix down due to the unfavorable diurnal timing...so although both Tuesday and Wednesday look like they could see afternoon RHs in the 30% rnage in some locations, confidence is increasing that true fire danger issues will not materialize.

Another reinforcing cold front is expected to arrive over the weekend, likely crossing the region from the north, re-establishing cold-air damming across the area. The breakdown of the upper blocking pattern, however, should finally allow better upper dynamics to arrive, and ensembles are in "okay" agreement that an uptick in low-level isentropic ascent may finally bring some rain to the region by the end of the seven-day forecast period.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR at all terminals today as a dry air mass remains in place across the area. Breezy NE winds are expected to persist through at least this evening, with gusts of 15-20kts already underway in many locations and likely to continue through the afternoon. Winds should slacken overnight, then pick up at 4- 8kts on Monday. Some FEW/SCT stratocu may develop east of the mountains again Monday morning, but the potential looks lower than the last two mornings owing to less of an easterly wind component. Given generally clearer conditions across the mountains than we've had the last two morning, the potential for valley fog looks greater, and MVFR to IFR restrictions appear likely at the mountain terminals before daybreak.

Outlook: Mostly VFR conditions are expected all week. Mountain valley fog and low stratus will be possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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