Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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197 FXUS62 KCAE 290509 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 109 AM EDT Mon Apr 29 2024 .SYNOPSIS... Weak high pressure centered northeast of the region will remain in control through Monday along with a warming trend. A weak front is expected to bring a chance of showers and thunderstorms late Tuesday into Wednesday, mainly northern and eastern areas. Above normal temperatures persist into the weekend. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... Satellite observations as of 8pm show clearing across the forecast area with weak high pressure continuing to ridge over the forecast area. HiRes guidance does point to the potential of some patchy stratus and maybe even some fog late tonight into early Monday morning. Fairly persistent forecast with lows in the mid-50s. && .SHORT TERM /8 AM THIS MORNING THROUGH TUESDAY NIGHT/... Monday and Monday Night: Generally quiet weather expected with an upper ridge axis over the forecast area. All of the active weather remains off to the northwest as a series of shortwaves move through the western OH and MS/TN Valleys on the west side of the upper ridge. Atmospheric moisture over our area with be slightly lower on Monday compared to today with PWATs falling below an inch through the day as low level flow shifts from southeasterly to more south or southwesterly. Due to low level moisture trapped beneath the subsidence inversion, would not be surprised to see some stratus in the morning. However, once any stratus burns off there should be some sunshine through the afternoon. Model forecast soundings indicate a strong subsidence inversion around 850mb which will limit instability. 850mb temps should warm a couple of degrees and with more sunshine this should result in warmer max temperatures in the lower to mid 80s. Dry weather continues Monday night with slightly warmer overnight lows in the upper 50s to around 60 degrees. It would not be surprising to see some predawn stratus develop along the Coastal Plain and move into the forecast area early Tuesday morning. Tuesday and Tuesday Night: Ensemble and global guidance is in reasonable agreement bringing shortwave energy into the forecast area from the TN Valley late Tuesday and Tuesday night which will bring an increase in rain chances. There are some timing differences among the faster GFS and slower ECWMF but this shortwave trough is forecast to amplify a bit as it moves into the area with the existing upper ridge shifting offshore and another upper ridge building over the MS Valley in response to deep upper troughing over the intermountain west by Tuesday night. Atmospheric moisture is forecast to increase to slightly above normal on Tuesday combining with upper forcing that moves in later in the afternoon to support at least scattered showers and thunderstorms across the region into Tuesday night. Deep southwesterly flow should yield some instability but the degree of instability may depend on how long it takes to erode the capping inversion around 700mb, and nevertheless should support possible thunderstorms, though the chance of severe thunderstorms seems unlikely. Temperatures should warm further with max temperatures in the mid to upper 80s, while overnight lows Tuesday night are expected to be in the upper 50s west to lower 60s east with lingering cloud cover and possible showers. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... There is somewhat lower confidence in rain chances on Wednesday as the slow moving upper trough traverses toward the coast due to timing issues with the guidance. Kept some low pops across the eastern Midlands, lower CSRA and Pee Dee region to account for possible slower timing. The western portion of the forecast area should have lower chances as some drier air begins to work into the region with a weak surface front/trough slowly pushing through the area by Wednesday evening. Ensemble guidance is consistent in showing another shortwave ridge building over the forecast area on Thursday and persisting into Friday with forecast soundings showing a strong subsidence inversion around 700mb. This will support continued above normal temperatures through the extended forecast period. Chances of rain will increase again over the weekend as shortwave energy from the west effectively weakens the upper ridge and 500mb flow becomes more zonal in nature giving way to additional shortwaves interacting with above normal moisture resulting in scattered showers and thunderstorms. Depending on the amount of instability available over the weekend, strong to severe storms cannot be ruled out and CSU ML probabilities are highlighting a potential threat, although confidence remains low this far out. Wednesday through Friday look to be the warmest days of the period with highs in the mid to upper 80s and cannot totally rule out a 90 degree reading, but with increased moisture and clouds and possible storms over the weekend, highs should be slightly cooler. && .AVIATION /05Z MONDAY THROUGH FRIDAY/... Mainly VFR. Patchy fog possible early this morning at fog prone sites AGS, OGB. Skies are mainly clear overnight. Pressure ridge along the coast extending into the area. Models show some increase in low level moisture toward morning. Some mixing expected in the boundary layer but surface winds already de-coupling. Nocturnal cooling may exceed the cross-over temps and soundings support at least a threat for some fog toward daybreak. No fog signal in mos, lamp or HRRR guidance. But based on persistence will mention a tempo MVFR fog at AGS and OGB 09z-12z. Expect scattered to possibly broken high based cumulus in the afternoon. Winds southwest to south 5 to 10 knots becoming southeast early in the evening. High clouds increase late in the evening. EXTENDED AVIATION OUTLOOK...Restrictions possible in early morning fog or stratus. Restrictions possible in scattered thunderstorms Tuesday afternoon and evening. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$