textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Precip probabilities for today have decreased somewhat.

In general, forecast temps have increased a degree or two for most days through mid-week.

KEY MESSAGES

1. A waning excessive rainfall threat early this morning, with areas of mostly light rain/drizzle expected at times through this evening. 2. Near-normal temperatures and dry conditions are expected for much of the work week, with little chance for precipitation.

DISCUSSION

Key message 1: A waning excessive rainfall threat early this morning, with areas of mostly light rain/drizzle expected at times through this evening.

The latest radar imagery and surface analysis depicts an outflow boundary moving steadily southwest across the southwest portion of the area early this morning. This is effectively pushing the backdoor cold front through the southwest third of the CWA, with cooler/drier/stable air filtering in from the northeast. Lingering, albeit steadily diminishing instability and very high moisture levels will continue to result in some degree of a heavy rainfall threat along and immediately north of the boundary...where cell movement has generally been very slow. However, the recent trend has been for cells to exhibit better movement in light of the faster movement of the boundary. An exception is across Oconee/Pickens Counties, where a small convective blob has been more or less anchored in the vicinity of a mesolow and weak upslope regime. The potential for excessive rainfall is expected to be largely confined to this area over the next couple of hours, although there is a non-zero threat of localized drainage issues in the urban areas across the GA and lower SC Piedmont. Overall, the excessive rainfall threat will continue to diminish and is not expected to last to daybreak.

Development of in situ cold air damming will result in cool/stable air encompassing virtually the entire CWA today...locations across the Smokies and vicinity being a somewhat notable exception. Max temps are forecast to be almost 10 degrees below climo in most areas outside the mountains...more like 0-5 degrees below normal across the higher terrain. Conditions will remain very moist, with precipitable water values AOA 1.75" expected to linger through the day. A low amplitude trough and associated entrance region of an upper jet will approach the region this afternoon, resulting in some increase in upward vertical motion. However, low level flow/forcing is expected to remain weak as pressures fall within in situ cold air damming region, such that little to no isentropic lift is expected. If anything, the flow above the surface-based stable layer is more downslope/WNW through a good chunk of the day. While chances of rain/drizzle should ramp up to the solid chance/likely range this afternoon, especially across the southern half of the area, the combination of weak forcing and stable air should preclude much of an excessive rainfall threat past early this morning.

The rain and drizzle will gradually diminish tonight as the upper trough axis shifts east of the area and significant mid/upper level drying occurs. Lingering low level moisture within residual in situ cool pool beneath this drying aloft will yield some potential for (at least) locally dense fog late tonight/early Monday.

Key message 2: Near-normal temperatures and dry conditions are expected for much of the work week, with little chance for precipitation.

In the wake of a departing upper trough, continental high pressure will steadily build into the region from the northwest early in the work week, with steady deep-layer drying expected to bring a return of mostly sunny conditions on Monday. This allow max temps to warm very close to climo during the afternoon. As the center of surface high pressure settles over the central Appalachians and Mid-Atlantic Mon night/Tue, temps are forecast to fall to around 5 degrees below climo before rebounding to near-normal levels as the surface high moves off the East Coast during mid-week. Temps are forecast to remain within a couple of degrees of normal through at least Friday. General weak surface ridging is expected to remain in place over the region through the end of the week, so conditions will remain dry and humidity relatively low. Global models are in general agreement that a southern stream disturbance will lift out across the lower Miss Valley next weekend, bringing more cloud cover, small PoPs and slightly cooler temperatures by Saturday.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: A backdoor cold front has pushed through much of the Terminal Forecast Area early this morning, although ample moisture persists north of the boundary. The bulk of scattered convective activity has pushed southwest of the TAF sites...KAND being a notable exception, but widely scattered showers/patches of mostly -RA could impact the other sites through 09Z or so. Otherwise, IFR cigs have, or will shortly encompass all TAF sites... possibly taking until 09Z or so to develop over KAND. Periods of LIFR cigs, as well as MVFR visby are possible as well. Only modest/gradual improvement is expected throughout the daylight hours, but most sites should see MVFR conditions by early afternoon or so. This could be short-lived, as the approach of an upper trough may bring a return of areas of mostly -RA/possible DZ...especially to the southern half of the area by late afternoon/evening. This will increase the potential for reduced visby to coincide with lingering low cigs. Cigs will likely settle at IFR or lower this evening, with increased potential for fog as conditions dry aloft, but the low levels remain very moist. Winds will remain NE 5-10 kt at most sites (light/vrbl at KAVL), becoming light/variable at all locations during the afternoon.

Outlook: Improvement to VFR is expected by late Monday. Dry VFR conditions are then expected to persist through the rest of the week.

GSP WATCHES/WARNINGS/ADVISORIES

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