textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes with today's forecast package.

The Aviation Discussion was updated for the 18z TAFs.

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 /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: Cirrus will continue to stream over the area though the period, with a convective Cu field underneath this aftn into this evening. Increasing moisture out of the west will be mainly mid clouds, which will limit fog potential even in the usual fog-prone valleys. Some guidance has IFR to MVFR stratus forming over northern GA that may expand east into the Upstate, but confidence remains low. Will add a FEW MVFR clouds to KAND Monday morning. Generally SW winds thru early evening, except more VRB at KAVL. A boundary will slip in from the NE by daybreak Monday, toggling winds out of the E/NE at KHKY, but may not reach KCLT. This boundary will be a focus for some convection late aftn around KCLT. Typical diurnal convection is expected to form across the mountains, but just beyond the 18z TAF period for KAVL.

Outlook: Diurnal convection and associated restrictions return Monday and continue thru the week. Widespread IFR ceilings across much of the area will be possible Monday night into Tuesday. Otherwise, Mountain valley fog and low stratus will be possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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