textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

1. Dry weather with comfortable humidity levels through Tuesday. Daily shower and thunderstorm chances return Wednesday and continue through the rest of the week.

DISCUSSION

Key message 1: Dry weather with comfortable humidity levels through Tuesday. Daily shower and thunderstorm chances return Wednesday and continue through the rest of the week.

Amplified upper pattern will persist over the CONUS through the first half of this week, with deep anticyclone remaining centered near New Mexico and closed low oer the eastern periphery of the Great Lakes. At the surface we will be on the cool side of a front stalled in the I-20 corridor. Today and Monday the pattern will support northwest winds, advecting dry continental air into the region. Profiles are unfavorable for deep convection with only shallow cumulus expected. Cold advection will be offset by insolation and downslope flow, such that daytime temperatures run near normal. Afternoon mixing should maintain low dewpoints in the lower 60s or even upper 50s. Overnight lows will be a few degrees below normal on account of the lower dewpoints and good radiational cooling conditions.

The upper pattern becomes less amplified over the area by Tuesday as the closed low drifts further east and its influence over the southern Appalachians diminishes. Broadly cyclonic flow will remain over the eastern half of the CONUS. Most guidance shows weak northerly winds at the surface, though winds aloft begin to favor southwest in response to more influence of the Plains ridge, and some moisture return aloft. In turn dewpoints rebound a bit though still mainly in the lower to mid 60s, while temperatures will remain near normal. This looks unlikely to have much impact on convective chances; more models/ensemble members depict our whole area remaining dry through Tuesday compared to yesterday's runs.

Weak sfc high in the Midwest is expected to fill and drift east by Wednesday; heights fall slightly aloft in the mid-MS Valley in advance of the next shortwave rotating into the broad trough. These changes effectively reactivate the front and bring it northward into our area; dewpoints and temps rise and diurnal showers/storms again appear possible. Interaction between the shortwave and the front suggests a continuing chance of showers/storms overnight into Thursday (when precip chances are greatest between now and next weekend). Though there are indications the passage of that shortwave may push the front back to our south and east at least briefly, it appears unlikely airmass change will occur. Hence we will remain seasonably hot and humid through the end of the period with a chance for primarily diurnal convection each day.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: A few low VFR cumulus will be seen around the area this afternoon. Winds will be predominantly out of the NE over the NC sites this afternoon and probably at the SC sites as well, though the latter are close enough to the stalled front south of the region that they have been SW'ly at times so far today. KAND should turn to NW for a time late afternoon, and KAVL will remain NW due to valley channeling, but otherwise all sites should be mainly NE overnight when not calm/VRB. Valley fog likely at least briefly at KAVL but otherwise VFR around the area thru the remainder of the period. Winds should mix to NW again by late Monday morning.

Outlook: No significant chance of convection until Wednesday with an even better chance on Thursday. Mountain valley fog and low stratus is possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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