Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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912 FXUS62 KGSP 191844 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 244 PM EDT Fri Jul 19 2024 .SYNOPSIS... A nearly stationary front will meander across our region through the first half of next week providing a focus for above-normal chances of mainly afternoon and evening showers and thunderstorms. Temperatures will be near normal or just a bit cooler than normal. && .NEAR TERM /THROUGH SATURDAY/... As of 2:25 PM Friday: Sct showers with some embedded thunderstorms have developed across our fcst area over the past couple of hours. A couple of storms have warranted an SPS, but we`ve yet to see any- thing stronger than that. Still expect coverage to increase thru the late aftn/early evening and then shift more over the eastern half of the CWA after that. Otherwise, broad upper trofing to our north will flatten/deamplify today and tonight as broad upper ridging persists to our west and to our east. A weak upper shortwave will lift over our area from the SW later tonight providing some amount of additional support for sct showers and thunderstorms. At the sfc, we will remain sand- wiched between weakening high pressure to our NW and the western extent of the dominate Bermuda High to our SE. A weak low pressure center will move off the NC Coast and along what`s left of a stalled frontal boundary today/tonight. With deeper moisture lingering over our region, we can expect another round of scattered to numerous showers and thunderstorms this afternoon and evening with showers likely lingering into the overnight. Despite the increased cloud cover today, there should be enough instability across our area for thunderstorms, but less instability compared to the past few days. In addition, lower amounts of dCAPE and effective shear should keep severe chances minimal at best. The main threat will likely be localized heavy rain with the potential for flooding. Convective coverage tapers off tonight but will likely linger into the over- night, especially over our eastern zones. Lows overnight should be near normal for mid-July, with areas of fog/low stratus likely developing again early Saturday morning. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 130 PM Fri: Not really any meaningful change in the forcing regime across the region thru Monday. Upper troughing generally will persist over the lower Mississippi Valley; as shortwave fills and/or advects toward the Mid-Atlantic coast late Sat into early Sun, weak height rises over the Southeast are soon negated by upper low swinging south out of the Missouri Valley. The seasonably diffuse boundary or convergence zone remaining from the central Gulf Coast to the VA/NC coast won`t become any better defined, but could pivot and/or shift slightly further north by Monday. Its presence near the region, combined with relatively deep SW flow and above-normal PWAT values, suggest elevated precip chances each day: basically likely for most of the Piedmont and categorical for the mountains. Any northward movement in the boundary would probably result in a slight uptick in daily dewpoints and PWAT, although only a minimal change in those fields is depicted in synoptic guidance, so we cannot say with much confidence that will actually increase precip coverage. Mean cloud-layer flow and deep layer shear are nonzero but small, so storms are likely to move only slowly, and could organize loosely into clusters. Widespread cloud cover should limit diurnal temps, keeping them 2-3 degrees below normal, and so diurnal CAPE should be on the low side for the season as well. Sfc-midlevel delta-theta-e values also will be muted on account of the moist profiles. Altogether main impact weather for the short term looks to remain locally heavy rainfall particularly where cells train. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 200 PM Fri: On a large scale, the overall setup remains in place through late next week: deep Bermuda anticyclone to our east, persistent trough centered in the mid-Mississippi Valley, and broad, ill-defined frontal zone in between, likely remaining just to our northwest. The Bermuda high does look to strengthen Tue-Wed, and that would seem only to push the front northward. However, by then some guidance members depict the upper low or another embedded disturbance moving toward the NE CONUS and driving the sfc boundary eastward thru the Mid-Atlantic. This could allow the peak convergence zone to shift back south into our area as soon as late Thursday, but if so it would probably stall SE of the Appalachians to end the week. Altogether, without a major pattern shift indicated by any of the available guidance sources, we can`t confidently advertise a significant trend in temps or precip chances. Daytime temps will remain a little below normal due to cloud cover; PoPs diminish slightly by Day 6-7 simply due to lower confidence with increasing forecast range. Main concern will be slow-moving or training storms producing locally heavy rainfall, and potential for deteriorating antecedent conditions following what will by then be almost a week under the influence of this moist and somewhat active pattern. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Expect another round of sct to numerous showers and thunderstorms and associated restrictions this aftn/ evening across the fcst area. This was handled with VCSH and TEMPOs for TSRA going thru roughly 23 to 24z. SHRA may linger overnight with at least MVFR cigs becoming IFR overnight with a decent chance for MVFR visby as well. Expect the lower cigs to linger thru late morning at most sites with VFR returning for the last few hours of the period. Winds will remain light thru the period and eventually favor a SWLY direction by the end of the period early tomorrow afternoon. Outlook: Expect sct to numerous showers and thunderstorms each afternoon/evening into early next week. Morning fog/low stratus will be possible each day, especially in the mtn valleys and over areas that received rainfall from the previous day. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...Wimberley NEAR TERM...JPT SHORT TERM...Wimberley LONG TERM...Wimberley AVIATION...JPT