Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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670 FXUS62 KGSP 240723 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 323 AM EDT Mon Jun 24 2024 .SYNOPSIS... A cold front will cross the area early this morning leading to scattered showers and isolated thunderstorms, mainly across the mountains. Drier and less humid conditions return behind the front this afternoon into Tuesday. Humidity returns again on Wednesday and lingers through the weekend. Another cold front will track across the area Wednesday night into Thursday bringing better shower and thunderstorm chances. Showers and thunderstorm chances may Friday into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM: A weak "cold" front is pushing into the area. A band of showers extends from near Hendersonville across the southern Escarpment into north GA. This activity will run generally into more stable air as it pushes further southeast, although in short term progs some moisture pooling is evident near the front and convection thus stands some chance of surviving for at least another hour or two. Downslope flow however will be an additional limiting factor, and thus it is not much of a surprise that CAMs depict the current activity fizzling before it reaches the I-85 corridor. CAM consensus does so far look to be timed well, although too focused on the NW NC Piedmont. Made another tweak to PoP trends to depict best coverage in the aforementioned areas, the western Upstate and Savannah Valley. Precip should be pretty much over for the lower elevations by 6-7 AM. Further upstream, some low cloud cover and spotty showers are seen over the Cumberland Plateau/Mountains; with upslope moisture remaining, saw fit to keep small PoPs until 8-9 AM along the TN border. The aforementioned moisture pooling will keep dewpoints elevated this morning, but diurnal mixing and developing NW winds will start to eat away at the moisture after daybreak. 850mb drying should set in by around midday as sfc high moves across the Ohio Valley, which will allow dewpoints to drop more appreciably. NBM temps proved just a little too cool yesterday, although the spotty cloud cover may have had a bit of impact. Debris clouds associated with the early morning precip should advect out during the early day, and although some diurnal cu will develop we will have plenty of sunshine this afternoon and continuing downslope. Temps should be somewhat cooler in the mountains/valleys, but for the Piedmont maxes end up about the same as yesterday. Dewpoints dipping into the upper 50s and lower 60s will keep heat index well below Heat Advisory criteria. As the high moves onto the Eastern Seaboard tonight, dveloping easterly flow might generate a few low clouds in our east, but likely of no consequence. The lower dewpoints will allow min temps to cool almost to normal for the Piedmont, and a couple degrees below normal in the mountains. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Key Messages: 1) Lower Humidity and Dry Weather Continues Tuesday 2) Humidity Increases East of the Mountains Wednesday Ahead of an Approaching Cold Front 3) This Front will also Increase Shower and Thunderstorm Chances Wednesday Afternoon into Wednesday night As of 200 AM Monday...Dry sfc high pressure will remain over the region Tuesday into early Wednesday before a cold front tracks across the western Carolinas Wednesday night. Lower humidity will stick around on Tuesday before increasing on Wednesday as winds turn SW`ly ahead of the approaching front. Highs on Tuesday should climb into the low 90s in the mountain valleys and low to mid 90s east of the mountains. Highs on Wednesday will be a few degrees warmer, climbing back into the lower 90s in the mountain valleys and the mid to upper 90s east of the mountains Wednesday afternoon. Thus, temperatures will remain well above climo through the short term. Heat indices should reach into the lower 100s in the Charlotte metro and the Upper Savannah River Valley Wednesday afternoon but should remain below Heat Advisory Criteria (Heat Advisory criteria begins at a heat index of 105 degrees). Dry conditions will linger through at least Wednesday morning before shower and thunderstorm chances increase from west to east ahead of the FROPA Wednesday afternoon into Wednesday evening. Convection will linger through the overnight hours on Wednesday as the cold front tracks overhead. Capped PoPs to chance (45% or less) area-wide Wednesday afternoon into Wednesday night as global models still diverge on the exact timing/coverage of convection. Guidance generally shows 20 kts or less of deep shear and less than 2,000 J/kg of SBCAPE ahead of and along the cold front Wednesday, so the severe potential looks to be low at this time. However, if storms are able to develop ahead of the FROPA during peak heating on Wednesday, a few isolated strong to severe storms cannot be entirely ruled out (with the main hazard being damaging wind gusts). The severe wx threat will be highly dependent on the exact timing of the FROPA so confidence on the severe threat remains low for now. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Key Messages: 1) Humidity Lingers East of the Mountains through the Long Term 2) A Cold Front Will Sink South of the Area Thursday into Friday but Shower and Thunderstorm Chances Linger Behind the Front 3) Another Cold Front Will Track Across the Area on Sunday Keeping Shower and Thunderstorm Chances Around As of 230 AM Monday...Hot and humid conditions, as well as above normal temps, stick around east of the mountains through the long term period. A cold front will gradually sink south across the eastern third of the forecast area early Thursday before pushing into the Coastal Carolinas early Friday. With dry sfc high pressure expected to remain just north of the Carolinas during this timeframe, shower and thunderstorm chances will linger across the area through the end of the workweek. Capped PoPs to chance (30% or less) area-wide for now. Heat indices should once again climb into the lower 100s each afternoon across the Charlotte metro and the Upper Savannah River Valley, but look remain below Heat Advisory Criteria for now. Another large upper anticyclone will build over the southern US on Saturday before gradually retrograding westward throughout Sunday. At the sfc, a cold front will track across the Midwest on Saturday before pushing across the western Carolinas on Sunday. This will keep shower and thunderstorm chances around through the weekend. Went with low-end chance PoPs (35% or less) on Saturday with higher chance PoPs (45% or less) on Sunday for now. Humidity looks to increase slightly this weekend which may allow for heat indices to flirt near Heat Advisory Criteria each afternoon in the Upper Savannah River Valley (Heat Advisory criteria begins at a heat index of 105 degrees). && .AVIATION /08Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Weak sfc front to cross the terminal area early this morning. This will bring an area of SHRA near KAVL and potentially KGSP/KGMU/KAND before dawn. An isolated TSRA is additionally possible, but confidence only high enough to mention this at KAVL. Lower VFR clouds will develop as the front passes the terminals, with a small chance of MVFR at KAVL as well. Winds will shift to NW after the fropa, but not expected to occur at KCLT until diurnal mixing begins around 13z. A very small chance of diurnal convection exists well south of KCLT and the SC sites today, but otherwise post-frontal drying and subsidence is expected to result in just cumulus. Development of easterly flow tonight could lead to some low VFR stratocu near KCLT/KHKY but of low impact. Brief mountain valley fog not out of the question at KAVL after 06z Tue. Outlook: Dry weather and suppressed convection again Tuesday. Widely scattered SHRA/TSRA may return as soon as Wed aftn/evening, with seasonable summertime weather returning then and continuing into the weekend. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...AR NEAR TERM...Wimberley SHORT TERM...AR LONG TERM...AR AVIATION...Wimberley