Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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747 FXUS62 KCAE 300813 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 413 AM EDT Tue Apr 30 2024 .SYNOPSIS... A shortwave trough aloft will push through the area Tuesday and bring scattered showers-storms in the afternoon and evening. Drier air will fill in for Wednesday and Thursday but temps will again push back in the mid-upper 80`s as ridging develops aloft. Shower-storm chances will gradually increase for Friday over the weekend as low level moisture returns and some weak troughs cross the region. && .NEAR TERM /THROUGH TONIGHT/... A robust short wave trough is evident over Mississippi this morning. It is already becoming a little negatively tilted. Moisture is increasing ahead of the trough across the Deep South into Georgia. Precipitable water will increase to around 1.4 inches, possibly a little higher in the CSRA and southeast Midlands as the surface ridge that is centered offshore weakens. The trough will move through South Carolina late this afternoon and this evening although appears to de- amplify a bit. Relatively strong upper lift expected ahead of the trough. Despite increasing high cloudiness, sufficient diabatic heating and modest warm advection should result in afternoon temperatures mainly in the low 80s. This will result in weak to possibly moderate instability with surface based CAPE likely above 500 J/kg especially in the CSRA and southeast Midlands based on latest CAMS. Overall mid level lapse rates appear weak limiting instability. Deep layer shear appears moderately high with HREF 0-6km values 25 to near 30 knots. The latest CAMS suggest scattered convective coverage, perhaps a little more coverage in the CSRA and southeast Midlands, less northwest into the SC Piedmont/north Midlands. Went ahead and raised the pops a bit across the area late this afternoon through the early evening when best forcing is expected. Severe threat appears low due to mainly weak instability. The showers and thunderstorms should diminish by around 03z but kept pops through the overnight with showers moving to the east. Overnight lows mainly in the low 60s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Excellent model-ensemble consensus is seen through the end of the week with deep ridging quickly building into the region as the 500 mb shortwave from Tuesday lifts northeast by early Wednesday. Dry and warm northwest flow from the surface through 250mb will help clear skies out on Wednesday and some downslope component flow will help further push temps back above average, in the mid- upper 80`s. The associated moisture gradient from the Tuesday trough passage will slide south to the GoM coast, driving dew points down into the 50`s throughout the day as surface winds remain out of the north- northwest. As we move into Thursday, broad ridging will deepen across the SE CONUS and the ridge axis will set up nearly directly overhead. So while the dry northwest flow will weaken, general subsidence will continue and skies will remain mostly clear again Thursday. Temps again expected in the mid-upper 80`s. Surface high pressure will strengthen a bit off the coast so surface winds will turn more out of the east in the afternoon and allow dew points to push back into the 60`s. && .LONG TERM /FRIDAY THROUGH MONDAY/... Broad ridging aloft is likely to dominate the long term period with gradually increasing low-mid level moisture; NAEFS highlights the relatively anomalously warm and moist setup through this period well with 50-90th percentile heights, temps, and PWAT`s. GEFS and EC members then consistently show a series of weak shortwaves sliding to our northwest starting late Friday through the end of the period. Given the warm and moist airmass in place thanks to the mid-level ridging and southwest surface flow, this shortwaves should serve as sufficient lift to trigger some scattered-widespread showers- storms each day in the long term. GEFS and EC particularly focus on Saturday-Monday afternoons for likely convection. Instability and shear look to be limited overall in this period however thanks to mediocre low-mid level lapse rates and very weak flow aloft. Joint probability in the LREF suite of > 500 J/kg CAPE and > 15 knots 0-6km shear remains less than 10% through the period (probs for greater than 500 J/kg alone are around 40-50% each day). So weakly forced showers-storms are probable in the afternoons, with limited severe threat. Regardless of precip chances, confidence is high in well above average temps through the end of the period with high temps running about 10 degrees above average, especially as we move into next week. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... VFR conditions expected through the early afternoon. Restrictions possible late this afternoon into the evening as convection moves through the area. High pressure offshore is extending into the area. The ridge will weaken this afternoon as an upper trough approaches the area. Satellite indicating mid and high level clouds will increase across the area through the morning. Some mixing in the boundary layer and less nocturnal cooling expected so fog not expected early this morning. The air mass will become weakly to moderately unstable by this afternoon. Scattered to broken cumulus possible late morning through the afternoon but should remain VFR. Ceilings more likely to be mid level. Convective models show scattered convection developing ahead of the upper trough late this afternoon into the evening. Brief restrictions possible mainly 20z-01z time period. Patchy light showers possible through 06z Wednesday. EXTENDED AVIATION OUTLOOK...Restrictions possible Tuesday night. Additional restrictions become possible again by Saturday ahead of a frontal boundary. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$