textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rainfall totals for Sunday afternoon and evening continue to trend downward, with the remaining hydro threat thus looking smaller and smaller.

The aviation forecast was updated to reflect the recent 18Z TAF issuance.

KEY MESSAGES

1. Dreary conditions continue today and tonight, but additional hydro issues are looking increasingly unlikely. 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: Dreary conditions continue today and tonight, but additional hydro issues are looking increasingly unlikely.

As we approach noon, the pattern continues to reflect hybrid cold- air damming, with a prominent surface ridge east of the NC Blue Ridge Escarpment, weak WSW flow on the 850mb chart, and a lax upper pattern with a de-amplifying z500 shortwave over the west-central Tennessee Valley. The stalled cold front, still just to our west, has begun to phase with the shortwave, and the two are beginning to inch eastward toward us at last.

The 12Z suite of model guidance depicts the continued eastward progression of the shortwave through this evening, until it's east of us by sometime after midnight tonight. There should be a good slug of synoptic-scale forcing during the afternoon and early evening hours, which should induce some degree of isentropic ascent...though apparently, per virtually all of the CAM guidance, not enough to spur much rainfall. Most of the CAMs feature too much of a westerly component to any weak warm advection, doing little to spur showers and perhaps even having a modest suppressive effect over the NC Piedmont. As a result, QPF continues to trend downward for this afternoon, with the bulk of guidance supporting only an additional few tenths of an inch of rain over the Smokies and Balsams, and perhaps an additional quarter inch or less over the far southern tier of the Upstate. The WPC's decision to remove the western Carolinas from the MRGL risk for excessive rainfall today was well-received, and seems in line with recent QPF trends.

By midnight, with the upper trough axis to our east, the atmospheric column will dry quickly, leaving behind a shallow layer of low-level moisture within a stable remnant wedge. Statistical guidance has begun to key on the potential for a round of locally dense fog and/or low stratus tonight, especially leading up to dawn when moist low-level air will be most exposed to the effects of radiative cooling.

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 /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: A soupy day continues for the western Carolinas. Still seeing widespread MVFR and IFR ceilings, and only very slow improvement as the day wears on. Some sites may return to VFR during the afternoon hours, but guidance is trending increasingly pessimistic, bringing into question whether we'll be able to get rid of these pesky MVFR ceilings. If VFR develops, which currently looks more likely in the Upstate than it does in the Piedmont, it'll be short-lived before ceilings crash again tonight. Another round of IFR clouds is expected after midnight. Rain chances, meanwhile, have sharply diminished for the remainder of the period, with some showers possible over the Upstate this even but only isolated activity elsewhere.

Improvement is expected on Monday improvement as a cold front finally ushers in a drier air mass. Winds will remain N/NE most of the day, while clouds will scour out...hopefully more quickly than today!

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.