Spartanburg, SC Weather

What Has Changed

Modified the cloud cover and ceiling forecast to account for unexpectedly-aggressive stratocu embedded in NEly flow east of the mountains.

Updated the aviation discussion for the recent 18Z TAF issuance.

Key Messages

1. Dry high pressure and inactive weather continue for most of the period. Low-end fire danger conditions may develop in some areas on Tuesday and Wednesday.

Discussion

Key message 1: Dry high pressure and inactive weather continue for most of the period. Low-end fire danger conditions may develop in some areas on Tuesday and Wednesday.

It's a beautiful day for most of the region Saturday, with only some lingering stratocu across the area owing to trapped moisture within a frontal inversion south and east of the NC mountains. After a chilly morning, most locations are warming up, and can expect to hit highs in the mid to upper 60s later this afternoon. Surface high pressure centered over New England has driven a diffuse backdoor cold front across the area, which should continue to keep us stable and dry this weekend.

Dry and quiet conditions are still expected to persist for most of the next week as upper-level blocking continues across the eastern 2/3 of the CONUS. Surface high pressure over the New England coast will permit a rare clear-sky cold-air damming wedge to strengthen over the weekend before the breakdown of the parent high allows it to falter going into Monday. By Tuesday, however, a secondary cP air mass will settle into the northeast, reinforcing the low-level dry air and interrupting the week's warming trend toward normal. Nonetheless, temperatures are expected to climb to near or even a couple degrees above normal by the end of the week.

A secondary, low-end concern will be RH values, especially on Tuesday. The arrival of the drier air mass will result in both lowered dewpoints and low-end wind gusts, which could contribute to elevated fire danger conditions in some locations. Confidence is limited at this point on timing, which in turn will dictate whether lowered RHs and any potential wind gusts overlap. The thinking remains that conditions are most likely to fall below criteria for any products, but the forecast will still be monitored closely.

Aviation

At KCLT and elsewhere: Mostly VFR conditions are expected for the 18Z TAF period. An unexpectedly persistent low-VFR to high-MVFR cloud deck remains in place across much of the terminal forecast area today, as ENE flow continues to drive upslope moisture into the region...and TAFs have trended more pessimistic for the afternoon as a result. Guidance remains confident that we'll at least improve to VFR over the next 2 hours, but then again that same guidance was confident that we'd be crystal-clear by now, so take it with a grain of salt. Once we return to VFR, we should stay there for the remainder of the afternoon and evening, with SKC conditions still expected for much of the overnight. Guidance has hinted once again at a developing deck of MVFR stratus east of the mountains Sunday morning, and given how much clouds have overperformed today...went ahead and expanded mention of these in the new 18Z TAFs.

Outlook: Mostly VFR conditions are expected all week. Mountain valley fog and low stratus will be possible each morning.