Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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798 FXUS62 KGSP 131753 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 153 PM EDT Sat Jul 13 2024 .SYNOPSIS... Hot high pressure will dominate the area into early next week, with only isolated showers and thunderstorms each afternoon. The pattern is expected to change mid-week as a cold front stalls across the area and brings above normal rain chances and cooler weather. && .NEAR TERM /THROUGH TONIGHT/... As of 140 PM EDT Saturday: Garden variety convection beginning to pop up in parts of the area, mainly over the BR Escarpment and Upper Savannah River Valley. Updated PoPs to reflect the current radar trends. Not expecting this activity to produce strong to severe storms, but a slight uptick in coverage is possible as we enter the peak heating of the day. Otherwise, a broad, low-amplitude long wave trough will remain centered west-through-north of the forecast area through the period. Weak subsidence and mid/upper level drying is anticipated in the wake of a disturbance that will lift away from the NC/ Mid-Atlantic coast today. As a result, forecast soundings are generally capped, albeit modestly unstable this afternoon. As such, convection- allowing models limit diurnal convective development to rather spotty activity over the mountains and foothills. PoPs are limited to 20-30% in these areas, with <20% chances across much of the Piedmont. Chances for severe storms are practically non-existent, and in fact thunder may be difficult to come by this afternoon, while the drier atmosphere will also limit the heavy rainfall potential. Max temps are expected to be around 5 degrees above normal in most locations, but deep mixing is expected to limit the potential for reaching the Heat Advisory criteria of 105, but some locations across the lower elevations of the Piedmont could reach the century mark for an hour or two this afternoon. Any convection should diminish quickly this evening, giving way to a warm overnight. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 155 AM Saturday: Synoptically, the majority of the CONUS remains under high pressure, including the southeast. The Bermuda high off the east coast churns and amplifies into Sunday as does the persistent anti-cyclone over the southwest. The CWA remains in a pattern of high pressure during the short term, keeping the area relatively dry and hot. Sunday looks dismal in terms of any precip chances. Sounding guidance has a batch of mid-level dry air atop a modest temperature inversion. Even if precip could form in the afternoon, the boundary layer has such a stout T/Td spread, anything that does fall through that layer should evaporate. The GFS and EURO do indicate an uptick in moisture with PWAT profiles reaching the 1.5-1.75 inch range east of the mountains, but this will not suffice. Rinse and repeat with very similar environmental parameters on Monday. Nothing of note with winds either, as the pattern remains in a very broad, stagnant summertime pattern. As for any heat index concerns, moisture return is slow and helps to keep values around the low 100s for a few areas south of I-85 and east of the I-77 corridor on Sunday. Monday could have a few areas in the eastern NC Piedmont approach 105 degree heat index values. Confidence is increasing on this given the strong height rises and persistent high pressure. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 205 AM Saturday: By Tuesday, high pressure continues to dominate the lower CONUS and keeps the area dry for the most part. Long term guidance shows little QPF response as a small signal over the mountains on Tuesday afternoon and to the south by the overnight hours. Again, similar to Monday, modeled soundings with abundant mid- level dry air and an inverted-V in the boundary layer. Confidence for any rain during the beginning of the week is very low given such strong chances for evaporation. However, a pattern swing by mid-week could be in the works. Long range guidance from the GFS/EURO signal a developing upper low and trough across Canada, north of the Great Lakes. This amplification could lead to height falls across the eastern portion of the CONUS, and spilling into the CWA starting Wednesday. A stronger cold front could make its way toward the CWA and stall by the end of the week. This pattern could create higher chances for more rainfall over multiple days. At the surface, amplifying high pressure off the east coast should setup a persistent SW flow and moisture advection into the area. But, as always, this is far out in the forecast time and will likely change. As for temperatures, Tuesday still looks to be the hottest day with actual temps reaching triple digits across most of the CWA east of the mountains. Heat index could be a concern as model guidance has trended more toward an increase in moisture content, especially east of the mountains. Heat index values of 105 are possible and confidence is increasing on this. Wednesday could also see another day of hot temps and similar heat index values of the day prior. The cold front looks to approach the CWA Wednesday night into Thursday, which should provide some heat relief to much of the area. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... At KCLT and elsewhere: VFR conditions are expected through the forecast period. Low-end VFR cu beginning to settle over most of the area, with isolated showers popping up. Decided to include a VCSH mention at KAVL through 01Z based on current radar observations and latest model trends. Also, included a TEMPO for -SHRA and associated restrictions at KAND through 21Z due to a few showers developing within 10 nautical miles of the terminal. Otherwise, confidence is too low for a SHRA/TSRA mention at the other TAF sites as the coverage will remain isolated. Winds continue to toggle mostly south to southwesterly through the evening before going light and variable overnight with mostly clear skies. Can`t rule out mountain valley fog and fog near bodies of water, but confidence is too low for a TAF mention at KAVL/KHKY/KAND at this time. Wash, rinse, and repeat for Sunday as isolated diurnal SHRA/TSRA will be in store with afternoon VFR cu and winds continue to run southwesterly. Outlook: Isolated/widely scattered diurnal showers and storms are expected mainly over the mountains early next week. Shower and thunderstorm are expected to increase during the latter half of the week as a cold front pushes into the region. Morning fog/low stratus will be possible each morning, especially across the mountain valleys and for areas that received heavy rainfall the day prior. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...TDP NEAR TERM...CAC/JDL SHORT TERM...CP LONG TERM...CP AVIATION...CAC