Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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245 FXUS62 KGSP 151606 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1206 PM EDT Mon Jul 15 2024 .SYNOPSIS... Hot high pressure lingers above the region through Tuesday. A pattern change starts on Wednesday with a cold front forecast to approach from the north then become stationary across our region for several days. Expecting waves of low pressure to move along the front enhancing the chances for rain. && .NEAR TERM /THROUGH TONIGHT/... Morning Update...Current obs are running below the fcst curve by 1-3 degrees across the area. However, some locales have lost cloud cover which will allow for a quick warm up this afternoon. Will be tricky with the heat index values, but being so close to advisory criteria have opted to extend the Heat Advisory into Mecklenburg county. Other surrounding counties likely wont have enuf coverage for an advisory mention. Otherwise, the atmosphere is forecast to destabilize more robustly, with the weak capping inversion that was seen over the past couple of days largely absent from this afternoon`s forecast soundings. A consensus of guidance sources, including convection-allowing models, support a solid 20% or so increase in PoP over what was observed Sunday, with 30-50% covering much of the area, except for 60% in the climatologically favored initiation zones closer to the Blue Ridge escarpment. The increased instability should support more in the way of strong storms today, while a couple of pulse severe storms are possible. With precipitable water values expected to creep up close to 2", a localized heavy/possibly excessive rainfall threat could materialize, especially with any cells anchoring on terrain features. Convection will diminish in typical fashion this evening, with another very warm and muggy night expected. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 150 AM Monday: Synoptically, the CONUS remains under high pressure, including the southeast. Flow aloft is weak Tuesday, but profiles start to really moisten up. Guidance from modeled soundings show another day with a stout inverted-V and around 1000 J/kg of muCAPE. There is less dry air aloft to mix down during the daytime, which suggests hot temps and hotter heat index values likely. Diurnally driven showers and thunderstorms are possible with higher chances (50-80%) in the mountains and (30%-50%) elsewhere. Despite the higher humidity, if showers can get going, this could reduce heat index values and provide some relief. Will continue to monitor. The heat is likely to continue Wednesday, but not be as hot as a pattern shift emerges. Long range guidance from the GFS/EURO signal a developing upper low and trough across Canada, north of the Great Lakes. This amplification leads to a trough dipping toward the south by the end of the this forecast period. Flow aloft shifts more SW as a cold front makes its way toward the area, stalling over Tennessee. Though QPF response isn`t high, highest PoPs over the mountains again (60%-80%) and (40%-50%) elsewhere for showers and thunderstorms. Overall, heat busting precip and height falls toward the end of the short term, sets up a rainy pattern in the extended. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 200 AM Monday: By Thursday, a weakened second trough begins to protrude southward and sets up a persistent SW flow and moisture advection into the area. Looking at long term guidance, this should be the overall pattern through the end of the forecast period. QPF response this far out at least shows rainfall, but how much cannot yet be determined with confidence as the forecast will change. Widespread PoPs each day with highest probability ramping up each afternoon, especially over the mountains. As for temperatures, expect a break from the heat for a while. Thursday will be the warmest of the stretch. After Thursday, temps should start to decline through the end of the weekend and into the start of next week. Though temps will be lower, humidity is not expected to decline as the front holds the dry air west of the CWA. Persistent moisture advection keeps the area muggy, but cool through the end of the period. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: VFR conditions are expected to persist through much of this forecast period. There is a little mountain valley fog and low stratus this morning, but this is expected to remain confined to the valleys west and north of KAVL. Otherwise, an uptick in coverage of diurnal convection is expected today above the past couple of days, and VCTS (early/mid afternoon) and Prob30s for TSRA (late afternoon/early evening) appear warranted at all sites. Convection will diminish during the evening, with little expected overnight. Winds will generally be calm or light/variable this morning, but will become SW at 5-8 kts during the afternoon. Outlook: Isolated/scattered diurnal showers and storms are expected mainly over the mountains through the middle of the week. Showers and thunderstorms are expected to increase in coverage during the latter half of the week as a cold front pushes into and stalls near 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...Heat Advisory until 8 PM EDT this evening for NCZ071-082. SC...None. && $$ SYNOPSIS...CP NEAR TERM...JDL/SBK SHORT TERM...CP LONG TERM...CP AVIATION...JDL