textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

A Frost Advisory has been issued for tonight for the northern foothills and northwest Piedmont of North Carolina.

PoPs have been increased across the mountains for Thu night/Friday.

KEY MESSAGES

1. Seasonably cool and dry conditions continue into early next week, with frost likely across portions of the area tonight and Sunday night. 2. Temperatures warm again into midweek before another frontal system increases precipitation chances and ushers in much colder weather late in the week.

DISCUSSION

Key message 1: Seasonably cool and dry conditions continue into early next week, with frost likely across portions of the area tonight and Sunday night.

Dry/cool surface high pressure continues through Sunday night, as a long trough axis steadily shifts off the East Coast. Max temps are forecast to be right around normal through Sunday, but low dewpoints, light winds, and mostly clear skies will result in rather large diurnal temperature ranges, with below normal minimums expected tonight and Sunday night. One potential fly in the ointment for tonight is the area of high clouds associated with the exit region of an upper jet over the Miss Valley...which is likely to stream over the area this evening into the early part of the overnight...which could conspire to briefly inhibit cooling. Nevertheless, there is some indication that any high clouds will move east of the area by daybreak...so temps could drop rather quickly around sunrise. While it's not a slam dunk...a Frost Advisory will be issued for areas along the I-40 corridor outside the mountains. Another Frost Advisory s likely Sunday night... perhaps for an even larger area, as guidance suggests even more ideal radiational cooling conditions.

Key message 2: Temperatures warm again into midweek before another frontal system increases precipitation chances and ushers in much colder weather late in the week.

An upper trough axis moves off the East Coast Monday, with low amplitude ridging developing over our region. Max temps are therefore forecast to rebound to around 5 degrees above climo for much of the area Monday, with those warm highs continuing through Wed. General low level ridging will persist over the southern Appalachians and vicinity, so dry air will continue to allow for large diurnal temperature ranges, with min temps expected to be around, or even a little below climo through mid-week.

By mid-week, a consensus of global models continues to advertise the building of a very deep ridge across the West, with a series of short wave troughs of an increasingly Arctic origin diving down the east side of this ridge carving out an impressively deep trough/upper low over the East by Friday. Associated frontal system is most likely to impact our region from late Thu into Fri. Global models continue to offer disparate solutions regarding the placement/timing/intensity of surface development across the Southeast/Mid-Atlantic...and therefore to what extent a moisture source can be tapped. The GFS continues to offer by far the wettest solution for our forecast area, with the ECMWF and Canadian solutions remaining quite dry. Where there is better agreement is in the potential for cold sector/northwest flow precip...including the potential for mountain snow...at least for the higher elevations. For now, PoPs remain mostly in the token small chance range...except for higher chances along the TN/NC border. Otherwise, much cooler conditions are forecast for late in the week, with temperatures currently expected to be a solid 10 degrees below normal.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

At KCLT and elsewhere: VFR is forecast to persist across the Terminal Forecast Area through this forecast cycle, as a dry air mass lingers over the region. In fact, other than a period of high thin clouds this evening, SKC is likely. Mostly Light N winds (except NW around 10 kts at KAVL) are expected through the afternoon, with winds becoming light/vrbl or calm this evening. Light SW winds may develop Sunday afternoon.

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

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Frost Advisory from midnight tonight to 9 AM EST Sunday for NCZ035>037-056-057-502-504-506. SC...None.