


Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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831 FXUS62 KGSP 261727 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 127 PM EDT Thu Jun 26 2025 .SYNOPSIS... The upper ridge which was responsible for the very hot weather we have had will gradually weaken, allowing temperatures to get closer to normal through the weekend. A disturbance meandering over the Deep South will help produce mainly afternoon and evening showers and thunderstorms each day. A weak cold front reaches our region by Tuesday and becomes stationary west to east through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 928 AM Thursday... Key Messages: 1) Hot and Humid Again but not as Hot or Humid as the Last Two Days 2) Heat Advisory in Effect from 2PM to 8PM Along the I-77 Corridor 3) Another Round of Strong to Severe Storms Develops this Afternoon and Evening but Coverage and Intensity Should be Less than Yesterday A couple stray showers continue to drift across the area with a couple returns over the mountains and another small shower over Lincoln County. Overall, the forecast remains dry through the rest of the morning before another round of diurnally driven storms this afternoon. No changes were needed with this update. Weak upper ridging remains over the eastern United States while a weak upper low lifts northward over Florida through the period. This will allow the heat and humidity to lower just a bit today (we will take any relief we can get at this point). Temps this afternoon will end up ~3-4 degrees cooler compared to yesterday but will still end up around 5-10 degrees above normal. Highs will range from the low to mid 90s east of the mountains and the upper 80s to lower 90s across the mountain valleys. Triple digit heat indices are once again expected, mainly east of the NC mountains. However, the Caldwell, Burke, McDowell, Rutherford and Polk mountain zones will see triple digit heat indices return today. Locations along/near the I-77 corridor are most likely to reach Heat Advisory criteria this afternoon/early evening so the Heat Advisory remains in effect from 2pm to 8pm. Heat indices in the advisory will range from 105-108 degrees F. Another round of strong to severe storms can be expected this afternoon and evening but activity is not expected to be a robust as what we saw yesterday. Although deep layer shear will increase slightly, ranging from 10-15 kts, both SBCAPE and DCAPE will a few hundred J/kg lower than yesterday. SBCAPE should generally range from 2,000-3,000 J/kg with DCAPE ranging from 900- 1,300 J/kg per the latest high res guidance and model soundings. The Day 1 SPC Severe Weather Outlook has the entire forecast area in a Marginal risk for severe storms and this appears warranted based on the expected environment today. Damaging wind gusts from microbursts will continue to be the main hazard with any severe storms that develop but isolated, brief large hail is also possible. The Day 1 WPC Excessive Rainfall Outlook has most of the forecast area in a Marginal risk so the isolated heavy rainfall/flooding threat will return again today (especially for areas that saw heavy rainfall yesterday and that get heavy rainfall again today). Drier conditions will gradually develop late this evening into tonight once convection wanes. Lows tonight will be similar to this morning, ending up around 5-8 degrees above normal. Patchy mountain valley fog and low stratus should develop again tonight into daybreak Friday. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 250 AM EDT Thursday: The pattern will remain unsettled with showers and storms expected again Friday and Saturday. Coverage should be enhanced with an upper diffluent pattern in between a weak upper low near FL and a flat trough over the Great Lakes. The typical mountaintop and lee trough convergence will be the triggers for convective initiation, and shear and thermal profiles will support a pulse storm mode. The NBM has categorical PoPs in the mountains tapering to likely in the Foothills and high-end chc southeast of I-85. This seems a little high, but over a 12-hour period, coverage may largely verify these values. A few strong wet microbursts can be expected both days from mid aftn to early evening. Also, weak steering flow and elevated PWATs will yield an isolated/localized heavy rain/flood threat. Temps will continue to be slightly above normal, with highs in the upper 80s in the lowest mountain valleys and lower 90s east of the mountains. Lows in the 60s in the mountains and generally 68-74 east. Dewpts do not mix out much either day, keeping heat indices elevated and possibly topping out in the 100-105 deg F range in the southern Upper Savannah Valley and the Charlotte area. But not expecting to need a Heat Advisory either day. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 300 AM EDT Thursday: A weak upper low will open up into a relative weakness in the subtropical ridge over FL/GA Sunday, while a northern stream trough digs into the Great Lakes and Ohio Valley. This set up should keep enhanced diurnal convection going thru the first half of next week. In fact, the deterministic guidance shows even more convective response Sunday thru Tuesday than what we`re expecting Friday and Saturday. The digging trough will bring a weak cold front SE toward the forecast area and may provide extra convergence for convection Tuesday. Pretty much every day has similar PoPs and temps, with a slight uptick in PoPs and a slight downward trend in max temps Tuesday. The above-climo PoPs may increase excessive rain/flash flood threats as we continue with this pattern. Sever threat should remain a few wet microbursts each day, with perhaps an increase in more organized storms Tuesday thanks to a little more shear and upper divergence associated with the digging upper trough. There is disagreement between the GFS and ECMWF on whether the cold front will push far enough thru the forecast area to dry us out and bring temps back to normal. The GFS hangs the front up across the Piedmont, while the EC pushes it to the I-20 corridor. It`s difficult for a front to clear thru the area this time of year, and the EC seems to be on the more amplified side of the LREF guidance on the 500 mb trough. So while PoPs are lower, they are still elevated for Wednesday (50-70%). && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... At KCLT and elsewhere: VFR conditions are ongoing at most terminals early this afternoon but another round of afternoon showers and thunderstorms is already underway. Temporary restrictions from thunderstorms will be possible at KAVL and KHKY over the next several hours. Activity may spread farther east through the rest of the afternoon with restrictions possible along the I-85 terminals. Any storms should dissipate this evening with loss of daytime heating. VFR conditions will prevail overnight with the exception of any patchy fog, especially in mountain valleys. Confidence is too low to warrant mention in any TAFs at this point. Another batch of afternoon storms will be possible again tomorrow. Outlook: Daily chances for afternoon and evening showers and thunderstorms continue into next week. Fog and/or low stratus will be possible each morning in the usual mountain valleys as well as near lakes and rivers. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Heat Advisory until 8 PM EDT this evening for NCZ036-037-057- 071-072-082. SC...None. && $$ SYNOPSIS...ARK NEAR TERM...AR/TW SHORT TERM...ARK LONG TERM...ARK AVIATION...TW