textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rain chances have diminished across the area outside of the mountains, mainly along the Tennessee border for Sunday.

Updated the aviation discussion for the 12Z TAF issuance.

KEY MESSAGES

1. Dry through at least Saturday. Trending drier Sunday through Tuesday so confidence on getting any rain remains very low. The next best chance for rain does not look to arrive until the middle of next week. Above normal temperatures expected, with the exception of Sunday.

DISCUSSION

Key message 1: Dry through at least Saturday. Trending drier Sunday through Tuesday so confidence on getting any rain remains very low. The next best chance for rain does not look to arrive until the middle of next week. Above normal temperatures expected, with the exception of Sunday.

Weak high pressure and warm thicknesses aloft remain in place through today ahead of a shortwave trough that moves across the Southern Plains. Expect temperatures today to be the warmest through the forecast period with most locations expected to be in the upper 70s to lower 80s for afternoon highs outside of the higher elevations in the North Carolina mountains, leading to values running 10-15 degrees above normal. A strong continental surface high (~1030mb) is expected to move into the northeastern CONUS Friday night into Saturday. In response, a backdoor cold front will move in from the north and allow for cooler, drier air to settle in for Saturday as afternoon highs rise only a few ticks above normal as the onset of CAD commences.

The aforementioned shortwave trough shifts from the Southern Plains into the Mid-MS Valley and Midwest on Saturday and continues pushing eastward towards the OH/TN Valleys and Southeast Sunday into Monday. An increase of upper/mid-level clouds will roam the skies during this time frame. Stout low-level dry air will keep the better moisture transport to the south while the associated forcing for ascent from the shortwave remains weak. Deterministic and ensemble guidance continue to show a mostly dry solution, keeping the deeper moisture shunted closer to the Gulf Coast and Florida. Only ~10-15% of ensemble members from the deterministic models depict measurable rainfall across portions of the CWA. As a result, mentionable PoPs have been taken out over most of the western Carolinas and northeast Georgia outside of slight chance PoPs over the Tennessee border counties Sunday evening into Sunday night. CAD is expected to be fully entrenched across the area on Sunday, leading to the coolest day of the forecast period, with most locations being at or slightly below-normal for afternoon highs.

Any lingering wedge should gradually erode Monday into Tuesday, allowing for temperatures to rebound back to 4-8 degrees above normal by Tuesday. Our next mid/upper trough will be in the midst of moving across the western CONUS Sunday and propagate to the central CONUS Monday and Tuesday, while most of the guidance closes off into a low as it marches east. At the surface, a deepening cyclone will develop over the Central Plains, while a secondary low forms over the Southern Plains and lower half of the MS Valley. An attendant cold front will move east across these same areas as well. Ahead of this system, the surface high over the northeast moves over the northwestern Atlantic, while southerly return flow brings a better moisture transport into the CWA. The overall timing and synoptic progression still differs amongst all guidance, but there is at least decent agreement for at least some precipitation by midweek next week. Severe weather can't be ruled out with this setup as deep layer flow will be enhanced. However, guidance only show very meager instability, if any at all as the cold front slides across the CWA late Wednesday into Thursday. Details in regards to this frontal system is still too far out for specifics.

AVIATION /10Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR conditions will prevail at all terminals through the TAF period. Scattered high clouds will continue to stream overhead with light winds through the day out of the northeast. Winds will increase overnight as a backdoor cold front drops across the area from the northeast. Otherwise, a few patches of mountain valley fog are apparent on pre-dawn satellite imagery, but should remain outside of KAVL.

Outlook: Dry and VFR through at least Saturday, outside of mountain valley fog. Rain and associated restrictions may return Sunday but confidence is now very low as the forecast has trended drier.

GSP WATCHES/WARNINGS/ADVISORIES

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