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Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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767 FXUS62 KGSP 141020 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 620 AM EDT Wed Aug 14 2024 .SYNOPSIS... Dry high pressure gradually builds in from the north through Thursday, resulting in mainly isolated afternoon showers and thunderstorms in the mountains. The high will drift east off the East Coast Friday, as a cold front approaches from the west over the weekend. The front will bring a return of better chances of shower and thunderstorms through Sunday, then lower chances early next week. && .NEAR TERM /THROUGH TONIGHT/... Key Messages... 1) Patchy to Dense Fog at Times Expected Across Portions of Western North Carolina this Morning 2) Below Normal Temperatures for Most Locations Today Despite More Sunshine 3) Isolated to Scattered Convection Possible Across the Mountains this Afternoon and Early Evening with Dry Conditions Expected Elsewhere As of 620 AM EDT Wednesday: Patchy fog and low stratus has developed this morning across portions of western North Carolina. Locally dense fog has developed across the northern NC Foothills with Hickory and Morganton both reporting dense fog. Thus, went ahead and issued an SPS through 9am for patchy to locally dense fog for locations along and north of I-40. Fog and low stratus should mix out by mid-morning. Otherwise, cloud cover will continue to gradually decrease through this morning. Temps are near to just below climo along/near I-77 and I-40, with temps running a few degrees above climo elsewhere. Dry conditions will persist area-wide through at least this morning. It will be sunnier today but highs across the forecast area expected to be near climo to a few degrees below climo. Slightly warmer temps are expected across the eastern half of the forecast area this afternoon, with the western zones seeing slightly cooler temps. 00Z CAMs show scattered convection developing this afternoon and early evening across the mountains, with dry conditions elsewhere. Thus, have chance PoPs in place across the western zones during this timeframe. With the HREF ensemble probability showing SBCAPE not exceeding 500 J/kg during peak heating, mostly showers are expected. However, an isolated thunderstorm cannot be entirely ruled out, mainly along the southern Blue Ridge Escarpment. Dry conditions can be expected tonight with the potential for another round of mountain valley fog and low stratus. Some fog may spill into the NC Foothills again but confidence on this is low for now. Lows tonight will remain a few degrees above climo across the western zones with low near climo to just below climo across the eastern zones. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 230 AM EDT Wednesday: Flat Upper ridging will build into the area Thursday into Friday from the Lower MS Valley, while a deep trough digs into the Upper Midwest. The trough will continue to dig into the Ohio Valley Friday into Fri night with the upper ridge axis shifting east off the East Coast. Meanwhile, a sfc ridge axis will be along the spine of the Appalachians at 12z Thursday, and shifts to the East Coast by 12z Friday, which will begin a weak return flow atop the forecast area. An area of low pressure will track across the Great Lakes, bringing a trailing cold front into the Ohio Valley on Friday. A moderately unstable warm sector air mass with some bulk shear upstream of the NC mountains may support organized convection, but confidence is low on surviving all the way to the mountains. But the mountains should see an uptick in convective activity with diurnal heating and a SWLY upslope flow. Less instability (and possibly some CIN) should keep the Piedmont largely quiet Friday. Temps will be a degree or two below normal Thursday and warm to near or slightly above normal Friday. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 245 AM EDT Wednesday: The main concern will be PoPs and any severe potential with a cold frontal passage on Saturday. A digging upper trough should provide DPVA for synoptic support, while SWLY low-level flow should bring in some moisture along/ahead of the front. The frontal forcing doesn`t look that strong, however. So not a slam dunk for severe storms, but probably will be at least a marginal threat. The 00z guidance has come into better agreement on the trough axis pivoting east to the Eastern Seaboard, allowing the front to reach the Carolina Coast Sunday into Monday. Drier air will filter in from the NW atop the forecast area and should cut back on diurnal convective chances for the first part of next week. Temps will be slightly above normal Saturday, then cool to near normal behind the front. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... Key Messages... 1) Patchy to Dense Fog at Times and Low Stratus are the Main Concerns through Daybreak at KHKY and KAVL this Morning and Possible Again Tomorrow Morning 2) Scattered Showers will Develop at KAVL this Afternoon with Dry Conditions Lingering Elsewhere 3) Mostly MVFR to VFR Cigs Expected through the 12Z TAF Period At KCLT and elsewhere: Dry conditions will continue through this morning. Patchy to dense fog and low stratus have already developed at KHKY, with only low stratus at KAVL so far. Have TEMPOs at both sites to account for the fog/low cigs. Went ahead and added TEMPOs for MVFR cigs at both KGSP and KGMU for this morning per the latest OBS and satellite imagery. Fog/stratus should mix out around 13Z- 14Z. Still seeing mostly MVFR to VFR cigs elsewhere this morning with mostly calm to light N/NE`ly across the terminals. Winds east of the mountains will remain NE through the morning hours before gradually turning more ENE/E this afternoon. Winds will then briefly toggle back NE this evening into late tonight. Winds at KAVL should gradually turn N/NE after daybreak. KAVL will then see winds turn SE`ly this afternoon into this evening before going calm to light and VRB tonight. Have a TEMPO for -SHRA at KAVL this afternoon as showers are expected to develop across the mountains. Dry conditions will persist elsewhere. Mountain valley fog and low stratus may develop tonight into daybreak Thursday, with KHKY looking to have a lower fog potential compared to this morning. Dry conditions are expected tonight into Thursday morning. Winds should gradually turn SE`ly across the terminals Thursday morning after sunrise. Outlook: Isolated diurnal convection returns Thursday. Coverage of convection increases Friday into Saturday as a cold front approaches out of the west. Patchy fog and low stratus will be possible each morning in the mountain valleys and in any locations that received heavy rainfall the day prior. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...ARK NEAR TERM...AR SHORT TERM...ARK LONG TERM...ARK AVIATION...AR