Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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399 FXUS62 KCAE 051137 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 637 AM EST Tue Nov 5 2024 .SYNOPSIS... High pressure will extend into the area from the northeast. Scattered light rain expected today due to moist onshore flow. A frontal boundary will approach from the northwest Wednesday into Thursday. As tropical storm Rafael moves northwest toward the Gulf of Mexico Wednesday from the Caribbean Sea, deep moisture is expected to spread north into the Georgia and South Carolina. This will lead to numerous showers late Wednesday into Thursday. Locally heavy rain will be possible. Moisture may linger into the weekend but showers will become more isolated. Temperatures are expected to be above normal. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Scattered showers, especially in the Midlands today. Scattered light showers and drizzle mainly in South Carolina counties this morning as onshore flow and isentropic lift continues over the forecast area. This has led to widespread low cloudiness as well. Temperatures remain on the warm side this morning as a result, in the mid 60s. Plentiful moisture today in the low and mid levels with a narrow band of highest PWATs between 1.4 to 1.5 inches over the Midlands. While overall lift will be relatively weak, there will be enough isentropic lift to support scattered showers. Surface high pressure remains centered near Bermuda which will continue to support onshore flow. As it moves slowly east, the strongest lift will shift a bit to the east as well where a surface trough will promote low level surface convergence. While rainfall amounts will not be overly impressive, HREF indicates high probability of at least a quarter inch today, centered along the I-26 corridor, which is substantially more rain than we`ve seen since late September. Precipitation expected to taper off tonight as isentropic lift weakens. Upper ridging remains over the area with 500mb heights well above average with NAEFS mean near the 99th percentile. This combined with the warm start to the day will lead to above average temperatures today with highs in the mid 70s to around 80, even with clouds and scattered showers. Lingering low clouds tonight with low temperatures remaining warm once again, in the low to mid 60s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Key Message(s): - Moderate rainfall expected. Locally heavy rain possible. Upper ridge off the coast of the Southeastern states with increasing southwest flow aloft. The surface ridge will be well east of South Carolina. Tropical storm Rafael is expected to be moving northwest through the northern Caribbean Sea during the day. Ensembles and deterministic models continue to show a plume of moisture ahead of the storm spreading north across the eastern Gulf of Mexico into Georgia and South Carolina. GEFS and EPS show precipitable water increasing to above 2 inches with highest confidence across the CSRA and southeast/central Midlands. This is also now supported by the HREF. So expect precipitable water near 300 % of normal by Wednesday night into Thursday morning. The axis of deeper moisture shifts to the east a bit Thursday. A frontal boundary will be approaching from the northwest Wednesday night and may set up across the area, likely enhancing low level convergence. Models show increasing isentropic lift/moisture flux with onshore flow late Wednesday into Thursday. Additional lift provided by weak mid level short waves in southwest flow aloft. Raised the pops a bit from previous forecast and trending toward widespread showers with highest confidence in the CSRA. WPC has put CSRA into the central Midlands in a slight risk of excessive rain. Ensemble QPF means are high but the distributions show large spread. Ensemble guidance mean total qpf 2-3 inches especially CSRA but median values a little lower due to positive skewness leading to outliers. Despite dry pattern of the last 30 days, there appears to be an elevated risk for excessive rain especially in the CSRA. The showers are expected to shift to the east Thursday afternoon. Temperatures will be still above normal despite rain and clouds. && .LONG TERM /FRIDAY THROUGH MONDAY/... Key Message(s): - Lower chances for showers but low confidence forecast. - Temperatures remain above normal. Flat upper ridge over the southeast with confluent flow to the north. Deep low in the Desert Southwest moving into the Plains over the weekend. Expect surface ridge to be build south into the Carolinas from the north. Front near the area Friday, possibly near the coast. Tropical Storm expected in the Gulf of Mexico. Scattered showers expected Thursday night. Ensembles keep lingering moisture across the area into the weekend but precipitable water slowly decreases. Uncertainty high early in the weekend due to tropical system in the Gulf. NBM keeps low pops into early next week with above normal temperatures. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... IFR Ceilings with Occasional Visibility Restrictions this Morning. Restrictions Redevelop Tonight. IFR ceilings are in place at all terminals this morning with scattered showers also leading to decreased visibility at times. As the plume of moisture over the terminals slowly shifts eastward, expect decreasing chances for rain and improving ceilings mid to late morning into the afternoon. VFR conditions expected at all terminals by mid to late afternoon with cumulus deck around 4kft. Tonight, while some drier air will likely move in aloft, lingering low level moisture will once again support restrictions developing. Uncertainty among models as to whether IFR or MVFR restrictions but based on persistence, mostly favored IFR ceilings. EXTENDED AVIATION OUTLOOK...Early morning restrictions continue to be possible as onshore flow continues into midweek. Increasing chance for rain and associated restrictions for the second half of the week. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$