textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

An Air Quality Alert was issued for the Upstate region of South Carolina for fine particulate smoke. The AQA is in effect until midnight EDT Thursday night.

KEY MESSAGES

1. Increased Fire Danger across the area through sunset, with a Fire Danger Statement in effect for our NC and GA counties until 8 PM. Very low-to-critical relative humidity is forecast each afternoon, keeping the fire danger elevated through Friday. Any fire that develops will catch and spread quickly. No outdoor burning! 2. Shower coverage across the region will become numerous on Saturday along and out ahead of an approaching cold front. Moisture returns later Monday ahead of the next front with showers redeveloping by Tuesday.

DISCUSSION

Key message 1: Increased Fire Danger across the area through sunset, with a Fire Danger Statement in effect for our NC and GA counties until 8 PM. Very low-to-critical relative humidity is forecast each afternoon, keeping the fire danger elevated through Friday. Any fire that develops will catch and spread quickly. No outdoor burning!

The fire danger will remain high through the end of the daylight period as any weak moisture return from the sfc high off the southeast coast will be offset by temps climbing up to about ten degrees above normal this afternoon. Occasional wind gusts of 15-20 mph will only make the situation more tenuous. Thus, the Fire Danger Statement remains in effect until 8 pm and outdoor burning should not be done.

The dry pattern will remain across the region as a mid/upper ridge moves from the Plains today, to the Midwest/TN Valley Thursday, to the Appalachians Friday, while steadily weakening the whole way. The position of a remnant sfc high well off the Southeast Coast should keep some weak moisture return ongoing across the region through Friday, but not at a rate that would offset the rising temps enough to improve the low afternoon RH problem. The model blend looks too optimistic with the dewpoint rises for Thursday and the driest guidance was blended in, which results in good confidence of another afternoon with min RH down in the 20-25 percent range. The potential for wind gusts looks low for Thursday afternoon, but with the ongoing dry weather situation, another statement for Increased Fire Danger should be expected. The temps should finally top out Friday afternoon about 10-15 degrees above normal, while dewpoints creep upward several degrees, such that our new forecast will indicate the near-critical RH only east of the mountains. That might be the last afternoon for increased fire danger. Some of the CAM guidance goes out into Friday afternoon and supports the idea of ridgetop convection over the NC mountains, especially near the TN border, so a slight chance of showers will be kept there. Bottom line...please refrain from any outdoor burning through Friday so as not to cause any wildfires.

As to air quality...smoke from wildfires over southern GA will eventually begin to impact our region, perhaps as early as Thursday afternoon over the lower Piedmont and Lakelands. The 12Z run of the HRRR shows a plume of high near-sfc smoke density emanating from southeast GA tomorrow and moving across the area from Abbeville and Greenwood toward Laurens/Union/Rock Hill tomorrow night.

Key message 2: Shower coverage across the region will become numerous on Saturday along and out ahead of an approaching cold front. Moisture returns later Monday ahead of the next front with showers redeveloping by Tuesday.

The inherited sensible wx forecast for Saturday remains virtually unchanged. Showers are still expected to become numerous, especially across the mountains, and as a ribbon of weak positive MUCAPE bubbles north in the piedmont, a few tstms may be embedded. QPF remains paltry, as there is a potential for deep convection to remain or become scattered east of the blue ridge in the afternoon leading to a few locales missing out on the brief wetting rainfall. The 22/00Z LREF QPF trend continues, limiting 30-50% probabilities for values exceeding half an inch to the Smokies.

After a brief period of post-frontal drying Sunday night, developing southerly flow atop departing weak sfc ridge is expected Monday. The early work week system is featuring low pressure lifting from the plains to the Great Lakes with an ever narrowing frontal band well south of the parent low. This frontal feature will affect the Southern Appalachians Monday night into Tuesday. With forcing for pcpn limited, it remains to be seen on just how much pcpn makes it east of the mountains. No surprises with respect for QPF probabilities from the 22/00Z LREF which still confine best chances for values exceeding on half inch to SW NC

AVIATION /19Z WEDNESDAY THROUGH MONDAY/

At KCLT and elsewhere: VFR expected at all terminals through the period, with a caveat. Eventually, visibility is expected to be impacted as smoke from wildfires over south GA drifts toward the Carolinas. For now, the guidance does not indicate problems, but it is a definite possibility that smoke/haze could begin to reduce the vis to the MVFR category by Thursday afternoon at the Upstate terminals and possibly even KCLT. Otherwise, only high clouds, and just a wind forecast. Most terminals will have occasional low end gusts from the SW thru early evening, then a light/variable wind overnight. Wind should not be as strong Thursday, still light SW.

Outlook: Dry, VFR conditions are expected to persist thru the work week as broad sfc high pressure lingers over the region. A frontal system is expected to bring showers and associated restrictions this weekend.

GSP WATCHES/WARNINGS/ADVISORIES

GA...INCREASED FIRE DANGER until 8 PM EDT this evening for GAZ010- 017-018-026-028-029. NC...INCREASED FIRE DANGER until 8 PM EDT this evening for NCZ033- 035>037-048>053-056>059-062>065-068>072-082-501>510. SC...None.