textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 00z TAFs.

KEY MESSAGES

1. Warm temperatures and near-critical RH expected again this afternoon. Bans on outdoor burning continue in both North Carolina and South Carolina. 2. Pattern change this weekend into next week with a welcome return of rain chances.

DISCUSSION

Key message 1: Warm temperatures and near-critical RH expected again this afternoon. Bans on outdoor burning continue in both North Carolina and South Carolina.

A slowly progressive upper level blocking pattern in the nrn stream supports one last day with temps getting up to 10 to 15 degrees above normal this afternoon. While the dewpoint continues to creep upward thanks to a light SSW sfc flow courtesy of weak high pressure off the Southeast Coast, the RH will once again fall down to near-critical levels during peak heating for one last day in this string. No Fire Danger Statements were issued because winds are light enough, though burn bans remain in place across SC and NC. Air quality alerts also remain in place in some parts east of the mountains.

Meanwhile, satellite and radar imagery show that convection has indeed formed across the ridgetops of NC, the extreme northeast part of GA, and downstream of the South Mtns. The convection was making the absolute most of the meager and shallow CAPE (around 250 J/kg) that is out there on the mesoanalysis, but we will take it. Precip probs were bumped up mainly at elevations above 3000 feet through peak heating. This is more a curiosity than anything, being that we've had so little rain lately. All this activity should end by sunset. Then...we await the approach of a front from the west.

Key message 2: Pattern change this weekend into next week with a welcome return of rain chances.

A long awaited pattern change is forecast to take place starting tomorrow into next week with cooler temperatures and a much needed return of rain chances. A large northern stream closed upper low continues to spin over the Canadian Prairies with a belt of southern stream westerlies extending from the Desert Southwest to the southeast states. A convective complex over Arkansas will drop into Mississippi this evening with CAMs in good agreement on the potential for an MCV to develop along the northern flank of the QLCS. Guidance lifts this feature across northern Alabama and northern Georgia tomorrow morning and across the forecast area during the afternoon. This will help foster the return of rain chances, especially across the mountains, as the MCV interacting with peak heating kicks off at least scattered to numerous showers and perhaps a couple thunderstorms. Associated cloud cover will also help to keep temperatures several degrees cooler compared to the last several days.

By early next week, a series of southern stream shortwave troughs are progged to slide across the Southern Plains and lift into the Southern Appalachians. The first of this activity may arrive as early as Monday night into early Tuesday morning. A frontal boundary may stall just to our west with subsequent shortwaves brining additional rounds of precipitation Tuesday into Wednesday before the boundary finally clear later in the week. How much rain we may see will depend on how convective elements evolve upstream, but hopefully we'll finally have appreciable widespread rainfall for the first time in weeks. Any severe weather threat also remains uncertain at this time range, but most certainly cannot be ruled out, especially if any organized upstream convection makes a run at the area.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: We're still seeing a few isolated showers over our area early this evening, but they should have no impact on any taf sites and should dissipate over the next hour or two. It looks like our SWLY winds have lost their low-end gusts since the sun set. They should go light and VRB to calm again tonight/ overnight and then pick back up from the SW by the early afternoon tomorrow. The approaching front will bring lower clouds from the west by the early afternoon tomorrow, with shower chances increasing from west to east during the afternoon. I have prevailing SHRA at KAVL beginning around 18z and at 19z for the Upstate terminals along with some low-end gusts. At KHKY and KCLT, prevailing SHRA begins at 21 and 23z, respectively. I also included a roughly 4 hr PROB30 for -TSRA at all taf sites as some amount of sfc-based instability will likely be present tomorrow. In addition, prevailing cigs are expected to lower to MVFR at KCLT late tomorrow night by the end of the taf period.

Outlook: Shower chances will taper off from west to east Saturday night. Generally dry, VFR conditions are expected to return for Sunday and Monday.

GSP WATCHES/WARNINGS/ADVISORIES

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