Area Forecast Discussion
Issued by NWS Greer, SC

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126 FXUS62 KGSP 231850 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 250 PM EDT Sun Jun 23 2024 .SYNOPSIS...
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A cold front will cross the area tonight and bring a chance of showers with isolated thunderstorms. Drier conditions return through Wednesday, before another active cold front moves in from the northwest Wednesday night into Thursday.
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&& .NEAR TERM /THROUGH MONDAY/...
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As of 245 PM Sunday: The KGSP radar shows that isolated showers have developed east of the mtns as of mid-afternoon, in an environment characterized by sfc-based CAPE on the order of 1000-2000 J/kg. Mid-level lapse rates are unimpressive, but low level lapse rates are steep and profiles show enough dCAPE, generally above 1000 J/kg, to suggest that if we manage to get a strong enough updraft to get a thunderstorm, and then perhaps some cloud ice, we could get strong enough downdrafts to produce some brief gusts that could knock down some tree limbs. Will add some wording about possible wind damage in the HWO. Precip probs will be kept in the slight chance range mainly over NC and along/N of I-85. As for the temps, yes it will be seasonally hot, but the RH looks like it will stay low enough to keep the Heat Index in check and below criteria. Meanwhile, a band of showers moving off the Cumberland Plateau was weakening as shown by most of the CAMs. Recent model trends for tonight and Monday continue in the latest forecast guidance. The main concern, albeit minor, is the thunderstorm chances over the mtns tonight. Models continue to show a vort lobe dropping in from the WNW tonight, digging a broad upper trof axis over the Mid-Atlantic region. The forcing should help to develop and bring a broken band of showers and thunderstorms into the area after dark, with some timing differences between the various CAMs. The expectations for any strong to severe storms are low as the timing is poor. A few of the showers might survive east of the mtns into the pre-dawn hours on Monday, especially over the NC foothills and NW Piedmont, but altogether no big deal and most places will stay dry. Low temps will be mild as the weak sfc reflection of this short wave will not cross the region until the hours around daybreak. In reality, this isn`t so much a cold front as it is more of a dry front, which is typical for this area at this time of year. Behind the boundary, a sfc high will build in thru Monday afternoon from the NW on the strength of an upstream ridge. The upshot is that temps Monday afternoon might ultimately be similar to Sunday afternoon, but the RH should be noticeably less (and less than we expected a few days ago), such that apparent temps should stay well below the Heat Index criteria. Precip chances will also be limited to a slight chance over the eastern-most zones in the middle part of the day before the boundary moves off toward the Coastal Plain in the afternoon.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 1230 PM Sunday...Upper heights will begin to rise early Tue which will support a Canadian sfc high to the north. This high will dominate the weather into Wed as it becomes reinforced and ridges down the east coast. Relatively dry and cool air will mix in, but still expect deep subs to allow for temps in the l90s east of the mtns and u80s across the mtn valleys. Soundings show mixing into the drier air aloft which will help keep sfc dwpts in the u50s to l60s and HI values below adv criteria. The atmos becomes more dynamic early Wed as a pos tilted h5 s/w pushes in from the west. This wave will likely produce sct showers and a few general to strong tstms across the NC mtns with isol activity east thru the day. Rainfall amts will be modest and wont make much of a dent in the below normal precip amounts received this month. Surface dewps will bump up in this environ ahead of the front and along with temps reaching the mid to upper 90s east of the mtns, heat index values could rise into advisory levels across the Lakelands. Overnight temps will remain rather warm with mins held abt 5-7 degrees abv normal. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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As of 205 PM Sunday...An upper trof axis continues to cross the area Wed night which will likely maintain chance thunder across the NC mtns and isolated storms east. With high pressure pushing a llvl convg zone into the area during the afternoon, expect another round of tstms across the NC mtns. Meanwhile, heights will rise as a subTrop ridge builds in from the west. This neg forcing will help keep tstm strength in the general category Thu afternoon and again Fri afternoon when the llvl flow brings in an upslope e/ly se/ly flow. The building ridge dominates the pattern into the weekend and makes for a summertime pattern with PoPs a little below climo and temps remaining above normal. Expect highs in the m90s each afternoon and lows likely held a couple cats abv normal. Heat indices look to remain below adv level Thu and Fri, yet may reach criteria Sat as dewpts surge ahead of a sfc front approaching from the northwest Sat night.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/... At KCLT and elsewhere: Each day the coverage of cu gets a little better across the region, so once again today we will contend with temporary VFR ceiling restrictions with a cloud base 040-050 through late afternoon. Radar shows isolated showers across the area, so most terminals get a VCSH until it looks more like one would actually impact a terminal, at which point we will amend. Wind should be SSW to SW through early evening. A better-defined band of showers and a few storms will move into the NC mtns this evening but should not make it past the mtns before falling apart. Have included a PROB30 for the mtn/foothill terminals to account for this. The showers will be ahead of a weak frontal boundary that is expected to move across the area in the early morning to daybreak, and the passage of the boundary should bring the wind around to W to NW by mid-morning. VFR thereafter. Outlook: Drying trend now expected to continue Mon-Tue with little to no diurnal convection those afternoons. Summertime humidity returns Wed-Thu with SHRA/TSRA chances also returning. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...SCW NEAR TERM...PM SHORT TERM...AR/SBK LONG TERM...SBK AVIATION...PM