Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 210051 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 851 PM EDT Fri Jul 20 2018 .SYNOPSIS... A weak upper wave of low pressure will move NE away from the forecast area this evening with drier air pushing in tonight and early Saturday. An upper trough and surface boundary will lead to chances of showers and thunderstorms late Saturday and Saturday night, and possibly into Sunday, with some storms possibly severe. A deep upper trough will then remain over the E CONUS into the middle of next week, providing a continued chance of showers and thunderstorms. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Regional radar this evening shows showers and thunderstorms have tapered off across the area. Surface low pressure centered along the southern South Carolina coast will lift northeastward toward the Outer Banks overnight. Drier air will gradually move in from the west on the back side of a weak upper level shortwave exiting the area. Most of the high-resolution models keep the area dry overnight. Have lowered pops over the next couple of hours. Some areas of fog late tonight southeast where heavier rain fell today. Overnight lows are forecast in the lower 70s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... A very weak ridge of high pressure will help to trap some low level moisture Saturday morning, allowing for plentiful low clouds, along with some areas of fog. However, as the atmosphere starts to mix by mid morning, the fog should burn off, and the sun will break through the low clouds, allowing for some typical late July heat to build. The increase in surface temp, along with plentiful low level moisture, will set the area up for a round of potentially severe convection in the late afternoon or evening. Add in some mid-level dry air and 0-6km shear approaching 40 knots with a jet on the south side of an upper low in the Ohio Valley, and you get the ingredients for some potentially significant winds. DCAPES will like be in the 1200-1500 range late in the day, and there will even be some modest veering of the winds throughout the lower layers, indicating the potential for an isolated tornado or two. It would not surprise me to see SPC raise part of the region into the enhanced risk category by tomorrow morning. Saturday night, the convection may linger for a while due to the synoptic support even with the loss of daytime heating, gradually diminishing after midnight. Clouds will likely hang on most of the night. On Sunday, some drier air will work into the area, so convection will be more limited. Wind fields will be weaker through the column as well. We will still be under the influence of cyclonic flow, so scattered afternoon convection will still be around, and one or two thunderstorms could produce a localized severe wind gust with DCAPES well north of 1000 by afternoon. Temps should be seasonable in the lower to mid 90s. On Monday, the upper low will begin to drop southward into the southeast, setting up deep southerly flow over the area. Afternoon showers and thunderstorms will be likely once again, with seasonable July temps. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The upper low will continue it`s trek southward, dropping into the eastern Gulf of Mexico for the first half of next week. Deep and moist southerly flow will continue over the area, with plentiful shower and thunderstorm activity. PWs will routinely be around 2 inches, meaning that we could start to see some locally heavy rain. Considerable cloud cover will keep maximum temps a few degrees below normal through at least the first half of the week with locations struggling to reach 90. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Low pressure will continue moving northeast away from the terminals this evening. The few lingering showers will dissipate over the next few hours. Drier air is moving into the area which will help prevent widespread ceiling restrictions as was seen last night. Although there may be periods of MVFR or IFR ceilings around sunrise. Models are also in good agreement with only a brief period of restrictions. The exception may be OGB which received a large amount of rainfall today. The amount of low level moisture may be enough to produce fog from 06Z-13Z. Upstream convection will approach the forecast area tonight from the west, dissipating through the night. At this point it appears unlikely that the thunderstorms will make it to the CSRA before dissipating. Dry air will continue to feed into the FA under west winds preventing precipitation through the rest of the morning. Saturday afternoon, the environment supports lines of thunderstorms progressing across the CWA from west to east. There is low confidence in the timing which prevents adding thunderstorms to the TAFs at this time. The most likely timing of thunderstorms is near the end of the 24 hour TAF period. .AVIATION /12Z TUESDAY THROUGH SUNDAY/... EXTENDED AVIATION OUTLOOK...Late night and early morning IFR to MVFR ceilings and visibilities possible Saturday and Sunday mornings at the terminals, especially OGB and AGS. Otherwise, restrictions will be mainly associated with scattered convection through the weekend and into next week. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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