textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Minor changes to PoP and rain/snow trends for late week.

Updated aviation section for 12Z TAF issuance.

KEY MESSAGES

1. Frosty temperatures are likely again tonight even as high temperatures warm above normal. 2. A strong frontal system increases precipitation chances late in the week, including the potential for mountain snow as much colder air overtakes the region.

DISCUSSION

Key message 1: Frosty temperatures are likely again tonight even as high temperatures warm above normal.

Heights will steadily rise, while a ridge of dry high pressure will remain over the Southeast through mid-week. The result will be highs warming to 5 and possibly up to 10 degrees above normal today through Wednesday. The dry air mass will support large diurnal temperature ranges, but with a warming trend as well. Good radiational cooling conditions will again support temperatures cool enough for frost formation across the NC foothills and northwest Piedmont tonight. Another Frost Advisory is likely but will not be issued until the after the current Frost Advisory ends. Incidentally tonight is the last night that Frost/Freeze products will be issued for any part of our area until the spring growing season begins.

Key message 2: A strong frontal system increases precipitation chances late in the week, including the potential for mountain snow as much colder air overtakes the region.

Global models remain in agreement in strongly amplifying the upper air pattern by mid-week, with a massive ridge building across the West. Multiple short wave troughs originating from increasingly higher latitudes will dive down the central-to-east part of the Conus during the latter half of the week, carving out of an anomalous long wave trough/upper low over the East by Friday. The associated arctic frontal zone is forecast to cross our area in the Thursday time frame. The attached surface low looks to move along the southern Great Lakes. The frontal zone occludes after it crosses the area with a strong low developing off the New England coast Thursday night into Friday. The guidance consensus continues to show little moisture inflow ahead of the front, keeping the chances for organized warm sector precip low. As a result, PoPs outside of the mountains are generally limited to 20-40%. The moisture inflow and forcing is better across the mountains, so categorical PoP is featured along the TN border. With the developing surface low, northwest/cold advection flow develops across the southern Appalachians and vicinity. This will interact with post- frontal moisture to result in upslope/wrap-around showers. With snow- levels falling quickly during this time frame, mountain snow showers are likely for at least the high elevations, and confidence is increasing that accumulating snow will occur. While confidence is highest that snow will accumulate above 3500 feet along the TN/NC border, accums are possible in favored valley locations of the TN border counties as well. Otherwise, temps will decrease from around normal on Thursday/Thu night, to a solid 10+ degrees below climo Friday through at least Sat night. Much of the area outside the mountains is likely to finally experience the first freezing temps of the season next weekend.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR through the period at all terminals courtesy of dry high pressure. Scattered low stratus near the big lakes early this morning could bring some brief low clouds to KAND. Some fog was noted at outlying areas of the CLT metro, but think it will stay away from KCLT. Fog in the upper reaches of the French Broad Valley will probably not make it to KAVL. Wind will be light/var or calm through mid-morning outside the mtns, then light NW during the late morning and afternoon, then light/variable again Monday evening. Wind should stay NW at KAVL through the period, with some occasional gusts expected during daytime heating.

Outlook: Dry and largely VFR through Wednesday, outside of some patchy mountain valley fog/low stratus each morning. A cold front may bring precipitation and associated restrictions Thursday into Friday but confidence is low at this time.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Frost Advisory until 9 AM EST this morning for NCZ035>037-056- 057-068-069-502-504-506-508. SC...None.