Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
761 FXUS62 KCAE 211035 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 635 AM EDT Sat Sep 21 2024 .SYNOPSIS... High pressure building over the region, resulting in generally dry and warm conditions through Sunday. A return to more seasonable conditions is expected early to mid week along with daily slight chances for showers. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Patchy fog possible early this morning. - Above average temperatures this afternoon. Through sunrise: Satellite imagery indicates there are a few pockets of fog and stratus developing across the forecast area. Expect fog and stratus to continue developing through the pre- dawn hours. After sunrise, the fog and low clouds are expected to dissipate rather quickly. Rest of today and tonight: A dirty ridge continues to slowly build over the area as an upper trough slides further eastward. As a result, temperatures are expected to be about 5 degrees above average for this time of year, topping out in the upper 80s to lower 90s. A shortwave is forecast to rotate around the periphery of the dirty ridge overnight, bringing shower or thunderstorm activity to North Carolina and Virginia. Confidence is low, but there is a small (~10%) chance that some of the activity is able to extend down to our neck of the woods. Have left mention of any rain out of the forecast grids for the time being. Tonight, temperatures are expected to be seasonably mild in the mid to upper 60s for lows. && .SHORT TERM /SUNDAY 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 coast further eastward. Surface high pressure centered over New England will remain in place across the Carolinas. Forecast soundings continue to show a capping subsidence inversion and this should limit convection both days, although on Monday afternoon there could be isolated showers or thunderstorms approach the northern Midlands associated with some weak shortwave energy rounding the top of the upper ridge, but think it will remain to the north at this time. 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. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Key Message(s): - Chances of rain increase on Wednesday 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 in the Gulf of Mexico. 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 brings a deeper upper trough to the east coast by Thursday with upper ridging over the Northern Plains and south central Canada, while the EPS splits off some of the energy from the base of the upper trough and closes it off over the Southern Plains by Thursday. This leads to lower confidence in the forecast, especially the pop forecast, but it seems 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 low developing in the southern Gulf of Mexico and possibly approaching the Gulf Coast by the weekend. The GFS and its ensembles have been trending toward a faster solution and bringing a system to the central Gulf coast sometime next weekend while the ECMWF and its ensembles have been slower and further west with this feature, but the latest 00z run of the EC has trended toward the GFS so this will be a feature of interest to watch in the coming days. 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 with increasing clouds and possible rain. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... Generally VFR conditions anticipated through the TAF period. Satellite imagery and surface observations indicate some patchy fog has developed in portions of the area. However, AGS is the only terminal affected thus far. There remains potential for some fog at the terminals through 13z or so, with the exception of DNL where the dew point depression is 3 degrees. Should fog form at any of the terminals, it will likely dissipate quickly after sunrise. VFR conditions persist after that. Winds are anticipated to be light, generally 5 kts or less. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected through Wednesday. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$