Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
721 FXUS62 KGSP 161042 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 642 AM EDT Tue Sep 16 2025 .SYNOPSIS... A coastal low meanders over eastern North Carolina through tonight keeping shower and thunderstorm chances as well below normal high temperatures around. The coastal low lifts northward towards the Mid- Atlantic mid to late week while weak surface high pressure builds back over the Southeast, allowing drier conditions to return. High Temperatures end up near normal Wednesday before trending above normal Thursday into the weekend despite shower and thunderstorm chances possibly returning over the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 640 AM Tue: Lingering showers early this morning west of the I- 26 corridor should dissipate by mid morning. Mountain valley fog will do the same. Another short wave is expected to rotate around the upper low over eastern NC and move across the area this afternoon and evening. The surface ridge over the area weakens as a low pressure system moves north across the northern NC coast this afternoon into VA this evening. There will be some moisture transport into the area on the easterly flow associated with the low, but deeper moisture and stronger forcing remain to our east. Still, instability is expected to develop once again, this combined with lingering low level moisture and forcing from the short wave, scattered convection is expected across the mountains and northern portions of the Upstate and NE GA. Isolated to scattered showers will move into the NC foothills and Piedmont on the easterly flow around the low. Overall, QPF will be light, but brief, heavy rainfall will be possible in any storm. Highs will be up to 5 degrees below normal, on the cooler side where clouds rotate in and showers develop. Showers taper off through the evening as instability weakens, and the short wave and surface low rotate away from the area. Some clouds will linger over the I-40 corridor but should clear out elsewhere. Mountain valley fog likely to form once again. Lows will be a few degrees below normal. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 100 AM EDT Tuesday... Key Messages: 1) Warming Trend Continues as Drier Conditions Return 2) Near Normal Highs on Wednesday with Above Normal Highs on Thursday 3) Humidity Increases Slightly Thursday, Mainly East of the Mountains The upper low lifts northeast away from the region while gradually weakening through the period. The associated coastal low lifts northward towards the Mid-Atlantic through early Thursday before taking a northeastward turn late Thursday into daybreak Friday while gradually weakening. Meanwhile, weak surface high pressure builds back over the Southeast allowing drier conditions to return during the period. Both the 00Z CAMs and 00Z global models depict the potential for some spotty showers to return each day but confidence is low as coverage should be lower compared to earlier in the week with both the upper low and coastal low lifting away from the region. The warming trend continues with temps ticking up a few degrees each day/night. Near normal highs are expected on Wednesday, with highs on Thursday running ~3-5 degrees above normal. Humidity increases slightly Thursday, mainly east of the mountains, as surface winds toggle southwest. Lows each night will remain a few degrees above normal. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 130 AM EDT Tuesday... Key Messages: 1) Warming Trend Continues through Friday 2) Cooling Trend Begins Saturday, Lingering through Monday 3) Mostly Dry Again Friday with Shower and Thunderstorm Chances Possibly Returning this Weekend and Lingering on Monday Weak upper ridging builds over the Southeast Friday into the weekend before upper troughing pushing towards the region Monday. At the sfc, a cold front approaches out of the north Friday into daybreak Saturday before the southwestern periphery of high pressure noses down into the Southeast Saturday into Monday. Mostly dry conditions linger through at least the morning hours on Saturday before shower and thunderstorm chances return the remainder of the period. However, confidence is low as 00Z global models are not in agreement regarding the exact coverage or timing of convection. 00Z global guidance seems to generally agree on PoPs returning Saturday. However, the GFS is dry Sunday into Monday while the ECMWF keeps wetter conditions around. The Canadian lies somewhere in between. Thus, NBM PoPs being limited to chance this weekend into early next week seems reasonable. The warming trend continues through Friday night before a cooling trend develops the rest of the period. Friday should end up being the warmest day of the week with highs trending several degrees above normal. Afternoon temps on Friday should climb into the mid to upper 80s across the mountain valleys and east of the mountains. Highs on Saturday should be a few degrees cooler but still ~4-6 degrees above normal. Despite the cooling trend continuing, highs on both Sunday and Monday should end up just above normal. Lows each night should remain ~4-7 degrees above normal. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: Isolated showers may bring a brief restriction to KAND this morning before dissipating. IFR cigs at KAVL will dissipate by mid morning and MVFR vsby at KHKY will do the same. VFR then expected through most of the day. Scattered diurnal convection develops over the western portions of the area. PROB30s in place for these. Showers should dissipate through the evening. Mountain valley fog likely again. With patchy fog possible elsewhere. Light N wind increases in speed with low end gusts this afternoon at KCLT. N wind for the rest of the NC sites through the day become light and variable overnight. Light N wind becomes NW to NNW for the SC sites during the afternoon, then light overnight. Outlook: Rain chances and potential restrictions will stick around Wednesday. Dry conditions then expected through Saturday. Some mountain valley fog will remain possible where clouds do not inhibit nocturnal radiation. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...AR NEAR TERM...RWH SHORT TERM...AR LONG TERM...AR AVIATION...RWH