textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated aviation section for 00z TAF issuance.

KEY MESSAGES

1. Seasonably dry and cool weather returns this weekend, with frost likely Saturday night and Sunday night. 2. High temperatures warm above normal again early next week before another frontal system brings small rain chances and much cooler weather late in the week.

DISCUSSION

Key message 1: Seasonably dry and cool weather returns this weekend, with frost likely Saturday night and Sunday night.

A long wave trough will continue to become established across the Eastern Seaboard through the weekend, with associated cool/dry low- level ridge forecast to gradually build over our forecast area. A return to near-normal temperatures is expected tonight and Sunday. The surface gradient is forecast to relax sufficiently for good radiational cooling conditions Saturday night and again Sunday night, when min temps are forecast at around 5 degrees below climo. This will create frost/freeze concerns for locations where the growing season is still considered to be ongoing (i.e., all areas outside the mountains.) At least Frost Advisory conditions appear likely across the I-40 corridor both nights, with lesser potential to the south and west. However, a freeze is certainly within the realm of possibility along the I-40 corridor, with some frost potential elsewhere. (Note: we will consider the growing season ended across our entire area when a freeze occurs or on 11 November, whichever occurs first.)

Key message 2: High temperatures warm above normal again early next week before another frontal system brings small rain chances and much cooler weather late in the week.

Long wave trough axis will shift off the East Coast Monday, to be displaced by a low-amplitude ridge across our region through mid- week. The low levels will remain dry, as surface high pressure is forecast to dominate over the Southeast and adjacent coastal waters. This will result in large diurnal temp ranges through mid-week, with max temps forecast to be a solid 5 degrees above normal Mon through at least Wed, while near-normal min temps are expected.

By late next week, the global models depict a very strong ridge developing across the West, with a series of short wave troughs of increasingly Arctic origin forecast to dive into the eastern half of the country by week's end. The result of this is an evolving consensus of an impressively deep trough developing across the East by Day 7. Associated strong frontal zone is currently forecast to cross our region in the Thu night/Friday time frame. In terms of PoPs, the devil is in the details, as questions abound regarding the timing/location of surface development and said surface feature's ability to tap into a moisture source. As such, the global models are a bit all over the map re: precip potential. For now, we limit PoPs to 20-30% and confine them to western NC Thu through early Fri. Regardless of how the precip scenario unfolds, much cooler weather is likely late next week, such that forecast maxes Friday are 5-10 degrees below climo.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: FEW clouds at 060-080 lingering over some of the terminal area as of 00z Fri in conjunction with weak shortwave overhead, so these likely will be short-lived. Mostly calm winds to start the period though some light SW winds will occur until the wave passes and NW flow overtakes the area, with speeds of 4-8 KT thru early morning; gusts likely will develop at KAVL and perhaps briefly at KGSP/KGMU. Still expect some upslope cloud production along the Appalachians which could spill over to KAVL at times, but bases likely will remain VFR and cigs intermittent. Fog still could develop in sheltered valleys but is not expected to threaten KAVL thru morning. Winds will remain mainly N to NE into Saturday, generally weakening during the afternoon but still potentially gusting at KAVL.

Outlook: VFR conditions expected this weekend into early next week. The exception will be a continued potential for morning mountain valley fog.

GSP WATCHES/WARNINGS/ADVISORIES

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