Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
054 FXUS62 KCAE 182357 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 757 PM EDT Wed Sep 18 2024 .SYNOPSIS... An upper low over the area will move slowly east to the coast by early Thursday. A few showers or thunderstorms are possible Thursday mainly in the east Midlands closer to the upper low. Moisture is expected to decrease Friday. High pressure will build into the area from New England over the weekend into early next week with dry and seasonable temperatures expected. && .NEAR TERM /THROUGH 7 AM/... Key Message(s): - Lingering scattered showers this evening An upper level low over upstate South Carolina has been moving slower than rush hour traffic the last couple of days, but finally shows some signs of at least drifting eastward this evening on the water vapor loop. Still, spokes of vorticity continue to rotate cyclonically around the upper low, and with precipitable water values in the 1.6 to 1.7 inch range, there is plenty of moisture around to allow for some scattered showers for a few more hours. Where it doesn`t rain, skies will still be mostly cloudy overnight. Late tonight after midnight, I do think we will see some patchy fog. We will have an extended period of very light to calm winds tonight, and we could start to get some subsidence as the final upper level vort pushes slowly eastward, setting up a nice inversion. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Key Message(s): - Isolated to scattered showers Thursday mainly in the east Midlands, drier Friday. - Seasonable temperatures. Thursday and Thursday night...Upper low will move into eastern North Carolina Thursday with long wave trough axis along the coast moving east in the morning. Moisture remains relatively high in the east Midlands with precipitable water near 1.75 inches. Models show a short wave trough moving through the area in the afternoon with the strongest lift focused closer to the Coastal Plain. Expect stronger diabatic heating than today across the region. Latest model forecast soundings for Thursday afternoon suggests moderate instability in the east Midlands with surface based CAPE around 1000-1500 J/kg. Weaker instability to the west due to lower moisture. Mid level subsidence inversion stronger in the west. So, a few light showers in the morning, then widely scattered/scattered showers mainly in the eastern area during the afternoon as moisture axis/short wave trough rotate through the area. Temperatures in the low to mid 80s. Convection should diminish in the early evening. Friday and Friday night...Low-level moisture remains high through the day especially in the east. Precipitable water only decreases slightly. There appears to be a weak cold front/moisture boundary moving south from eastern North Carolina in the afternoon. Latest GFS/Nam suggest a few showers may develop in the east again as another short wave moves through upper trough, but appears more focused in the Coastal Plain potentially aided by sea breeze convergence. The NBM pops are quite low and mean CAPE lower than Thursday. Any convection should be isolated. Temperatures a little warmer than Thursday. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Key Message(s): -Drier into early next week with warming trend over the weekend The ensembles continue to be in good agreement. Upper trough off the east coast with upper ridge over the southern Plains building east but flattening with time. Surface high ridging down the Eastern Seaboard. Low-level moisture remains high, high level moisture may increase by early Monday as the ridge flattens. Ensemble qpf probabilities > 0.1 inch only 10-20 % Sunday/Monday. NBM pops very low at this time so will continue dry forecast. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Restrictions expected during the early morning through mid morning hours. Upper level low continues to spin over the terminals while slowly moving eastward. Satellite and radar imagery shows a couple showers across the area and with sunset the remaining cells are beginning to diminish. Expect the showers to end by 03z with no impacts to the terminals with the main focus being the early morning stratus and fog potential. With plenty of moisture in the low levels and similar conditions to last night expect another round of stratus and fog to develop with indications for IFR and possibly LIFR around daybreak. Have generally kept with previous thinking and adjusted times slightly. Restrictions will begin mixing out shortly after sunrise however will take until mid to late morning before all sites return to VFR. Winds on Thursday generally becoming north to northeast around 5 knots behind the departing upper level system with skies clearing late in the period from west to east. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected through Monday. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$