Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 180139 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 939 PM EDT Thu Aug 17 2017 .SYNOPSIS... A surface pressure trough will linger in the forecast area through early next week. Upper ridging over the region will weaken somewhat Friday and Saturday, and then become a little stronger early next week. The pattern supports partly cloudy skies with scattered mainly afternoon and evening thunderstorms. It will be hot with heat index values peaking 100 to 108. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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A few leftover convective debris clouds and a weak low level jet will inhibit early morning stratus/fog development. Model guidance also suggests a lack of early morning fog and stratus. Overnight lows will again be very mild with temperatures in the mid to upper 70s, near record values. Record highest lows for CAE and AGS on August 18 are 77 degrees and 78 degrees respectively.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/... A weak cold front will approach the area by Friday evening. Expect scattered afternoon and evening thunderstorms due to the usual daytime heating surface instability. Precipitable water around 2 inches supports heavy downpours with the thunderstorms. However, shear will be weak and instability should remain limited with relatively warm mid-level air, so there is a low threat of severe thunderstorms. It will remain hot with maximum heat index values 105 to 108, just a little below the heat advisory criteria of 110. The front will stall between Columbia and the coast on Saturday. This will be a focus for more showers and thunderstorms, mainly in the afternoon. Model guidance has shown a drying trend for Saturday and Sunday, pushing the drier air further south over the past few runs. 90 percent of the European Ensemble members and all of the GEFS members suggest pops no higher than 40 percent across the eastern Forecast Area (FA) and no higher than 25 percent across the western FA. Reduced pops based on the model trends and ensemble spread but kept them on the higher end for consistency. Temperatures on Saturday and Sunday may not be quite as hot as Friday, but heat indices will still be 100 to 105 degrees. && .LONG TERM /MONDAY THROUGH THURSDAY/... Upper ridging will continue to build over the area on Monday as surface high pressure strengthens over the western Atlantic. Low- level moisture should remain high due to a southeast flow off the ocean. The pattern supports partly cloudy skies with a chance of mainly diurnal afternoon thunderstorms. Similar conditions are expected on Tuesday. Another weak front will approach on Wednesday, and thunderstorms will remain possible. Upper level troughing should remain in place over the eastern U.S. on Thursday, therefore showers and thunderstorms will continue. It will remain warm through the period with high temperatures in the low 90s and heat index values in the low 100s. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Generally VFR conditions through the period except possible restrictions in thunderstorms. Isolated convection winding down this evening...therefore not mentioned in TAFs. Light winds forecast overnight. Fog/stratus not expected overnight with a low level jet around 15 knots and some lingering convective debris clouds. Diurnal cumulus clouds should begin develop around 15Z with strong heating and winds becoming west to southwest 5 to 10 knots. Conditions favor isolated to scattered convection developing during the afternoon. Have included VCSH at all after 17Z. EXTENDED AVIATION OUTLOOK...Scattered mainly afternoon and evening showers and thunderstorms possible each day. Also, low-level moisture could result in early morning fog and/or stratus. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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