Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
691 FXUS62 KCAE 220625 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 225 AM EDT Sun Sep 22 2024 .SYNOPSIS... High pressure building over the SE US will keep warm and dry conditions in place through Sunday. A return to more seasonable conditions is expected early to mid week along with chances for showers. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... Key Message(s): - Partly cloudy with near normal low temperatures Weak high pressure will remain over the area overnight. Some moisture increase in the mid and upper levels as remains of convection well northwest of the area moves through the region. Expect the bulk of the clouds associated with the convection to move north of the area and with current weakening of the convection and the mountains yet to cross do not expect any showers through daybreak. Overnight lows will be in the mid to upper 60s. && .SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/... Key Message(s): - Upper ridge dominates over the area with above temps The upper ridge axis will build over the forecast area this period while shortwave energy dives southeastward through the Mid-Atlantic region on Sunday and shifts the upper trough off the Mid-Atlantic coast. A series of shortwaves will continue to spill over the ridge Sunday and Monday before the ridge axis shifts off the southeast coast. Surface high pressure centered over New England will extend southward and along the coast of the Carolinas into early next week. Forecast soundings continue to show a capping subsidence inversion and this should limit convection on Sunday but this feature weakens Monday and Tuesday. PW values remain around 1.5 inches on Sunday, but do increase along the SC/NC border on Monday/Monday night to around 2.0 inches. The atmosphere appears to be too capped on Sunday, but by late Monday afternoon/evening there could be a few isolated showers/thunderstorms across the northern Midlands. The rising 500mb heights should support continued above normal temperatures with highs expected in the lower to possibly mid 90s on Sunday. Monday high temperatures may be a bit cooler across the northern Midlands due to slightly cooler 850mb temps but highs should range from the mid 80s north to lower 90s south. Overnight lows will also continue above normal with temperatures upper 60s to lower 70s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Key Message(s): - Chances of rain increase by midweek with limited confidence - Continued above normal temperatures The extended forecast features a lot of uncertainty regarding the evolution of the upper level pattern and possible tropical development near the Yucatan Peninsula. Medium range ensembles diverge on the 500mb pattern evolution beyond Thursday after being in reasonable agreement earlier in the week. The upper ridge axis shifts east of the forecast area Tuesday afternoon allowing for increasing chances of rain with deeper southwesterly flow and PWATs rising to around 130-150 percent of normal. The GEFS/CMC/ECMWF all try to bring a trough into the central portion of the country then cut the system off by mid/late week. However, the depth and location of this development differs from model to model and run to run. Additionally, the high pressure ridge along the southeast coast settles differently depending on the model. This leads to lower confidence in the forecast, especially the probability of precipition through the period. It does seem reasonable that chances of rain will increase later in the week given increased moisture and may be reasonable to expect isolated diurnal convection late in the week. The other uncertainty in the forecast revolves around a possible development of low pressure near the Yucatan Peninsula moving into the Gulf of Mexico by mid/late week. The deterministic and ensemble forecasts indicate something over the eastern half of the Gulf of Mexico during the period, but timing and location still very uncertain. It will most likely take the system to actually begin forming for the models to have a better handle on timing and location along with the developing mid/upper level pattern across the eastern portion of the country. Temperatures are expected to remain above normal and warm with NBM probabilities of max temperatures above 85 degrees at 80% or higher across most of the area through Thursday. Slightly cooler temperatures expected by Friday and Saturday with increasing clouds and possible rain. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... Generally VFR conditions anticipated through the TAF period. Satellite imagery showing some mid level clouds north of the terminals but these should move over the region by sunrise if it holds together. A 30 knot low level jet should prevent significant predawn fog but cannot rule out some brief MVFR vsbys at prone AGS. A weak shortwave over eastern TN is expected to shift southeastward through the day and may spark isolated convection this afternoon during peak heating across the eastern Midlands and CSRA. Will include VCSH at OGB/AGS/DNL from 19z-00z time frame. Otherwise partly cloudy skies expected with some mid level clouds associated with the mid level trough and scattered cumulus clouds after late morning as temperatures rise. Light and variable winds around sunrise expected to become more westerly around 5 to 6 knots through the afternoon with CAE/CUB possible shifting more northwesterly or northerly as the upper trough moves through. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected through Wednesday. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$