textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12Z TAF issuance.

KEY MESSAGES

1. Cooler high temperatures return this weekend into early next week as cold air damming develops. Temperatures very gradually rebound through midweek ahead of the next frontal system. 2. Rain chances return middle of next week as a low pressure system approaches out of the west.

DISCUSSION

Key message 1: Cooler high temperatures return this weekend into early next week as cold air damming develops. Temperatures very gradually rebound through midweek ahead of the next frontal system.

Backdoor cold front will slip across the CWA tonight as a stout continental surface high (~1030mb) moves towards the northeastern CONUS. In this case, cooler, drier air will filter into the low-levels and allow afternoon highs to settle at or slightly above normal for today, with some low-end gusts from the northeast. At the same time, an open shortwave will traverse east of the MS Valley today and move 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. Very few ensemble members from the deterministic models depict measurable rainfall across portions of the CWA. As a result, mentionable PoPs are just about completely out of the forecast for late Sunday into Monday. Some of the run to run trends in the deterministic models show blips of precip, across portions of the CWA. However, confidence is too low to pinpoint exactly where in the aforementioned areas would likely receive any precipitation, so the current PoP forecast looks good, with isolated coverage expected. 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 through early next week, allowing temperatures to gradually rebound each day through Wednesday during the new workweek to slightly above normal values.

Key message 2: Rain chances return middle of next week as a low pressure system approaches out of the west.

The 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, ahead of the system. The overall timing and synoptic progression still differs amongst all guidance, but there is 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 shows meager instability, if any at all as the cold front slides across the CWA Wednesday into Thursday. Details in regards to this frontal system is still too far out for specifics.

AVIATION /10Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: VFR conditions will prevail at all terminals through the TAF period. High clouds will continue to stream across the region as a backdoor cold front pushes through from the northeast. Winds will be out of the northeast behind the front with low-end gusts expected at most terminals through the afternoon hours. Light winds returning overnight into early Sunday morning.

Outlook: Mostly dry and VFR through Tuesday. Cannot entirely rule out restrictions early next week but confidence is low. Otherwise, rain and associated restrictions should return middle of next week. With cloud cover expected this weekend into much of next week, mountain valley fog formation should remain limited.

GSP WATCHES/WARNINGS/ADVISORIES

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