textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The Aviation Discussion was updated.

KEY MESSAGES

1. Mainly diurnal shower and thunderstorm chances return Monday and continue through the week.

DISCUSSION

Key message 1: Mainly diurnal shower and thunderstorm chances return Monday and continue through the week.

A sharp trough will drift east into the Ohio Valley to the Deep South, working to split an upper ridge. This trough will stall over the Southeast, remaining as a weakness within the broader upper ridging across the eastern CONUS thru Wednesday. Deeper moisture and lower heights within this feature will help bring back mainly diurnal convection across the forecast area starting Monday. At the sfc, a weak front will slip south/southwestward across the Mid-Atlantic tonight and stall out roughly across the NC Piedmont. Plenty of cloud cover will also spread in from the west and help keep max temps a few deg below normal in the far western zones, while above normal temps are expected along the I-77 corridor. Severe chances will remain low, as instability will be modest, shear weak, and DCAPE on the low-side given deep-layer moisture. A marginal excessive rain/flash flood threat may develop Monday aftn and continue thru Tuesday, as convection will have efficient rain rates. PWATs will be up around 2" and storms will be slow-moving. Guidance is hinting at a fair amount of stratus development overnight Monday night and slow to erode thru the day Tuesday. Despite this, scattered to numerous showers and a few storms are expected across the area. Highs Tuesday look to be a few deg below normal under mostly cloudy skies.

Upper ridge begins to build back into the area Wednesday and the stalled sfc front washes out. PWATs remain high, but the pattern supports a more typical diurnal convective coverage each day thru the end of the week. Temps will warm above normal with muggier conditions. Heat index values expected to creep into the mid to upper 90s across the Piedmont, but not expected to approach advisory criteria of 105.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: A broad area of cirrus will continue to stream over the area from the west as a broad area of showers with some embedded thunder is expected to remain just to our west tonight and early tomorrow. Increasing moisture from the west will bring increasing mid-level clouds, which should limit fog potential overnight, even in the usual fog-prone mtn valleys. More of the latest near-term guidance has MVFR clouds reaching our western zones early tomorrow afternoon. As such, I have KAND going BKN024 around 17z with cigs lifting to 035 tomorrow evening. The lower cigs could reach KGSP, KGMU, and KAVL, but my confidence wasn't high enough to include in their TAFS. Otherwise, convective chances increase tomorrow afternoon as the airmass moistens. I have PROB30s for -TSRA at all TAF sites beginning between 18 and 21z. The best convective coverage is expected over the NC mtns tomorrow, but PoPs weren't quite high enough to go with a TEMPO for TSRA at KAVL. Winds will remain generally SWLY this evening, going light and VRB to calm later tonight. A boundary will move into our fcst area from the NE around daybreak toggling winds out of the E/NE at KHKY, but not expected to quite reach KCLT. This boundary could be a focus for some convection during the late afternoon around KCLT. Otherwise, winds will favor a SE to SW tomorrow aftn/evening with speeds around 5 kts at most sites.

Outlook: Diurnal convection and associated restrictions are expected each day this week. Widespread IFR ceilings will be possible late Monday night into Tuesday. Otherwise, mtn valley fog and low stratus will be possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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