textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated wording for tonight into early Monday with cold-air damming not looking as likely to scour out overnight.

The aviation forecast was updated for 00z TAFs.

KEY MESSAGES

1. Cloudy conditions through tonight with areas of fog, possibly dense in some spots, near daybreak Monday. 2. Following a brief bout of cooler conditions, temperatures return to normal mid-week. Dry conditions persist through this week, with little chance for rainfall.

DISCUSSION

Key message 1: Cloudy conditions through tonight with areas of fog, possibly dense in some spots, near daybreak Monday.

Per water vapor imagery the primary shortwave axis appears still to be west of the Appalachians, while attendant cold front appears it may have reached far western NC and north GA, though flow is very weak along it. A band of light precip will work its way across the southern CWA ahead of the shortwave, aided by the remaining upglide over the CAD wedge. Motion of the shortwave is slow enough--and winds aloft so weak--that it looks like the wedge may hang on until very late tonight if not the early part of the day Monday. While low clouds scattered late Sunday afternoon over much of our area, it appears likely low ceilings will redevelop as the rain tapers off and with whatever radiational cooling occurs beneath the cirrus deck. Areas of fog still look to develop particularly in the SW NC mountain valleys and areas of NE GA and the southern Upstate where the rain helped moisten the boundary layer. Can't rule out some dense fog though there is uncertainty given the possibility of cigs forming instead, and with the wedge not looking to shallow out as quickly as previously thought.

Key message 2: Following a brief bout of cooler conditions, temperatures return to normal mid-week. Dry conditions persist through this week, with little chance for rainfall.

Not much change to the long-range forecast this afternoon. Ensembles are still in good agreement on the arrival of a dry cP air mass on Monday as heights flatten aloft and give way to steady WNW flow and generally dry conditions, to persist most of the week. By Wednesday evening, the parent high will shift off the Mid-Atlantic coast, leaving a remnant stable air mass stagnant over the Southeastern US. Temperatures still look to be below normal on Tuesday, but climb to within a category of normal by Wednesday, and may return to normal or even slightly above normal by Thursday and Friday, as the air mass slowly modifies.

A moisture-starved cold front is progged to arrive in the Saturday/Sunday timeframe, with ensembles generally agreeing that the resident air mass will remain too dry for much if any rainfall to develop over our area. The front should, however, reinforce the cooler air in place across the area, and early projections put temperatures a solid two categories below normal by Saturday night and Sunday...though confidence is limited, and at this timescale the details can change.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Cirrus deck continues to stream over the area with scattered MVFR level clouds underneath, forming a cig at times. Cold-air damming (CAD) hangs on by a thread, but with weak winds at the surface and aloft overnight, think the moist airmass will remain in place. A band of light rain will occur over the southern parts of the area, prevailing -SHRA at KAND and perhaps briefly sprinkling at KGSP/KGMU. May come close to KCLT but not likely enough to mention. As the rain exits or tapers off later this evening, think the remaining MVFR clouds will fill back in and eventually lower to IFR near daybreak, along with MVFR fog in most areas but IFR at KAVL and KHKY. The IFR should lift back to MVFR or low VFR in the early day as northerly winds and surface warming finally scour out the CAD, with the cirrus also diminishing with time. Mainly calm/VRB winds tonight prevailing NE during the day.

Outlook: VFR conditions prevail all week. Mountain valley fog and low stratus will be possible each night.

GSP WATCHES/WARNINGS/ADVISORIES

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