textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12Z TAFs.

KEY MESSAGES

1. Above average rain chances and below normal temperatures continue through much of the week.

DISCUSSION

Key message 1: Above average rain chances and below normal temperatures continue through much of the week.

Early morning water vapor satellite imagery depicts a pronounced trough extending down the spine of the Appalachians. This feature is sandwiched between two upper ridges with one over the Desert Southwest and another just offshore over Bermuda. Heading through today, the main trough lifts northeast across New England but leaves behind a piece of energy in the base of the trough that becomes cutoff from northern stream flow. Guidance is in good agreement that an upper low will close off by this afternoon and will be stuck over the Southern Appalachians through at least mid week. By Wednesday into Thursday, an approaching longwave trough over the Great Plains will finally pick up and absorb the piece of energy, but will continue to foster at least some degree of troughing/weakness between the two pesky upper ridges.

The aforementioned synoptic pattern will favor a continued unsettled pattern across the region with the upper low supporting above normal diurnally driven rain chances each day with lower heights and sufficient cloud cover helping to keep temperatures below normal. The deep plume of moisture that extended across the area this past weekend has shifted east with a reservoir of lower PWATs (below 1.5") shifting across the Upstate and Piedmont today. This will keep the highest rain chances confined to the mountains and adjacent foothills. Coverage in diurnal showers and thunderstorms expands on Tuesday as the upper low evolves and fosters the return of east/southeast flow and moisture return. PWATs return to 1.75-2" across much of the area with at least numerous to widespread showers and storms expected. As with any summer storms, multiple days of showers and thunderstorms would support the potential for locally heavy rainfall and isolated flash flooding potential. Any flood threat should remain fairly isolated and mesoscale driven and not widespread. Additionally, an isolated strong to marginally severe storm with locally damaging winds cannot be ruled out any given day, but the overall environment will not be conducive for a more organized severe weather threat with rather lackluster thermodynamic parameters.

AVIATION /06Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: A myriad of restrictions will plague all terminals through the rest of the overnight into Monday morning as a deck of low stratus builds across the region. Ceilings are expected to fall to at least IFR, if not LIFR. At least several instances of patchy fog will also be possible, but confidence is lower. Ceilings will gradually lift through the morning with a return to VFR by the afternoon. Another batch of afternoon/early evening showers and storms is expected again tomorrow, but will be mainly confined to the mountains and the immediate foothills. Thus, the most likely terminal to experience impacts will be KAVL, but isolated to scattered coverage cannot be discounted at KHKY and KCLT. At least some degree of low stratus and patchy fog will likely develop again Monday night into Tuesday morning, but confidence in coverage and timing is low at this time.

Outlook: Daily showers and thunderstorms, along with associated flight restrictions, linger through at least mid to late week. Patchy fog and low stratus possible in the mountain valleys each morning, and wherever heavier rainfall fell the previous evening.

GSP WATCHES/WARNINGS/ADVISORIES

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