textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Low temperature tonight has been lowered by another few degrees. The Freeze Watch has been upgraded to a Freeze Warning. To the east of the Warning, a Frost Advisory has been issued from extreme northeast Georgia, across the upper French Broad Valley, and extending across the northern Foothills of North Carolina.

KEY MESSAGES

1. In the wake of a strong cold front, temperatures will be much cooler across the area through the weekend. Much of the NC mountains will drop down below freezing tonight and widespread frost is expected in extreme northeast GA, the upper French Broad Valley, and the NC foothills.

DISCUSSION

Key message 1: In the wake of a strong cold front, temperatures will be much cooler across the area through the weekend. Much of the NC mountains will drop down below freezing tonight and widespread frost is expected in extreme northeast GA, the upper French Broad Valley, and the NC foothills.

Now that a strong cold front has moved east of the fcst area early this morning, the cool-down will commence by daybreak. A few short linear segments of showers were noted on radar, with additional light rain upstream closer to the DPVA associated with the main upper short wave approaching from the west. The guidance shows a broad band of light precip developing over the east side of the fcst area in the pre-dawn hours as forcing improves with the wave passage, mainly in the form of low level isentropic upglide. Much of this light shower activity will be along/east of I-77 at daybreak, and much of the cloudiness will depart to the east shortly thereafter. High pressure will build in from the NW and N through the day after the upper wave moves away to the east. Indications are consistent that high temps will be 20 degrees or so cooler than yesterday in spite of plenty of sun this afternoon.

The main concern comes tonight as the pressure gradient relaxes and sky clears out. Even though the high center remains well to our north, radiational cooling should be effective enough to allow temps to drop down at or below freezing across most of the mountains. The downward creep of low temps continues again this cycle. The consensus was to lower the low temps tonight below what is seen in the NBM, which tracks because we often underestimate the cold air in these early autumn events. Thus, the Freeze Watch will be upgraded to a Freeze Warning. To the east of the Warning, frost looks like a good bet away from the thermal belts, so a Frost Advisory will be added.

Beyond that, the upper pattern grinds to a halt as the strong upper wave closes off an upper low that should move across the Mid-Atlantic region today and then set up shop off the Eastern Seaboard through the middle of next week. Modification of the air mass allows for temps to rebound by 3-5 degrees the next few days to the point we should be back to normal by Tuesday or Wednesday. No precip is expected. Some frost/freeze concerns are possible again Sunday night, but temps will not be quite as cold. We will wait and see how we fare tonight before acting on any additional advisories.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Gusty NNW to NNE winds expected thru the aftn hours across the area. Plenty of mid clouds with some lower VFR-level clouds across the Piedmont, with MVFR and lower cigs in the mountains. Light rain has broken out and is crossing KCLT at the time of 12z TAF issuance, but should quickly exit east within an hour or two. Chances of any MVFR or lower restrictions at KCLT continue to decrease, so no mention in the latest TAF. The clouds will linger thru the morning, then should start to clear out in the aftn, leading to SKC by early evening. Strongest gusts expected during the aftn, then gradual weakening with light N/NE winds overnight.

Outlook: Breezy NE winds expected again across the Piedmont Sunday aftn. Otherwise, dry, VFR conditions expected for most of next week. Mtn valley fog and low stratus will be possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

GA...Frost Advisory from 1 AM to 9 AM EDT Sunday for GAZ010-017. NC...Frost Advisory from 1 AM to 9 AM EDT Sunday for NCZ035-064-065- 501>507-509. Freeze Warning from 1 AM to 9 AM EDT Sunday for NCZ033-048>053- 058-059-062-063. SC...Frost Advisory from 1 AM to 9 AM EDT Sunday for SCZ101>103.