Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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542 FXUS62 KCAE 151035 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 635 AM EDT Sun Sep 15 2024 .SYNOPSIS... There will be a chance of showers and thunderstorms each day through early next week with deep moisture over the region. Drier air may move into the region mid-week lowering rain chances. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Mostly cloudy conditions. - Periodic light showers are possible this evening. Surface high pressure remains centered across New England, while a developing area of sub-tropical low pressure will be off the southeastern U.S. coast through tonight. This will keep a tight pressure gradient and somewhat gusty winds across the region. The developing surface low is forecast to track towards the coastline of SC late tonight, but should remain offshore. The surface high should prevail through the day, allowing only a few isolated showers to move into the eastern cwa through the day. Better moisture increase should occur overnight into early Monday morning as the low moves closer to the coast. So, mainly slight chance pops today and early tonight, then increase to chance pops towards Monday morning across the east and northeastern cwa. As for temperatures, below normal readings will continue again this afternoon with highs mainly in the lower 80s. Lows tonight fall back into the mid to upper 60s. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Key Message(s): - Periods of heavy rain possible Monday and Monday night Low pressure is expected to move onshore between early Monday morning to Monday night. Models continue to differ on the strength and trajectory of this surface low. Ultimately this low will be the main influence on the sensible weather for The Midlands and CSRA in the short term. However, the uncertainty in the exact strength and track lowers confidence in the amount and location of any potential heavy rainfall. The most likely area for rainfall will be across the Pee Dee region with lower rain chances to the southwest. An isolated thunderstorm will be possible but the steeper lapse rates should remain east of the forecast area. Mostly cloudy or overcast skies and potential rainfall should keep temperatures well below normal, in the mid 70s, for much of the area and upper 70s in the CSRA. Moisture could linger across the region for Tuesday as the low pulls away from the forecast area. A few showers will be possible but overall rain chances are lower as the deepest moisture shifts north. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Key Message(s): - Drier weather expected for mid-week - Forecast uncertainty increases for late week As a surface low moves north of the forecast area by mid-week, relatively dry air is expected to wrap around the system and move into the forecast area. Mean PWAT values from the GEFS and ECMWF ensemble generally decrease through the week but remain within 1.25 to 1.5 inches. With no strong forcing mechanism expected through Thursday this should limit rainfall chances. The pattern becomes more uncertain toward the end of the week with ensemble members showing a larger spread in temps and atmospheric moisture as mean 500 mb heights lower over the region. So there will be at least a slight chance of showers and thunderstorms through the extended. With drier air over the region mid-week, we may see temperatures rise to near normal with less cloud cover, otherwise below normal temperatures are expected for daytime highs. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... MVFR ceilings will continue through the morning hours, then a return to vfr expected by this afternoon. Potential again for mvfr late tonight into Monday morning. Developing surface low remains off the southeastern coast the next 24 hours. Meanwhile, strong northeasterly wind flow associated with an area of high pressure centered across the Mid-Atlantic will continue. This will keep a tight pressure gradient across the forecast area, and thus strong winds and wind gusts will continue through the period at all sites. Scattered showers remain closer to the coast, with a few isolated light showers near the Midlands terminals this morning, so can not rule out a brief passing shower through the period at any site. Will include initial vcsh at cae/cub due to regional radar showing light showers near those terminals. At remaining sites, confidence not high enough to mention timing at this time. Increasing rain chances possible near the end of the 24 hour taf period as moisture from offshore surface low moves further inland. As for ceilings, mvfr conditions will prevail through about noon. Guidance then shows improvement back to vfr after noon, similar to the past several days. After sunset, mvfr ceilings will then return towards 03z Monday. EXTENDED AVIATION OUTLOOK...Scattered showers with possible restrictions at times through Monday as moisture pools over the area along a front and low pressure near the southeast coast. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$