Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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124 FXUS62 KCAE 051721 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 121 PM EDT Fri Jul 5 2024 .SYNOPSIS... Moisture increases into the weekend with isolated to scattered showers and thunderstorms each day. Above normal temperatures are expected again Saturday with Heat Index values up to 110 possible. Atmospheric moisture remains high through the long term supporting a chance of showers and thunderstorms each day. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Heat Advisory in effect Friday for heat indices 105-110 across the entire area. Ridge axis remains across the region this afternoon, yielding intense heat and humidity across the forecast area. Temperatures are already in the upper 90s, with dewpoints in the mid to upper 70s. This is creating dangerous heat, and the Heat Advisory remains in place until this evening. Instability has been quicker to develop this afternoon, though, and agitate cumulus is actually being noted across the Midlands as of this writing. Some isolated to scattered showers and storms may develop here, but better chances for storms are possible this evening. A line broken line of thunderstorms (not severe in nature at this time) is more concise and a bit faster than most CAMs in the HREF had it across N GA and E TN. This will likely continue to move eastward given the uncapped, unstable air ahead of it in SC. I see no reason why this wouldn`t at least bring some showers or storms to the western Midlands and CSRA this evening, and this idea is supported by some CAMs despite them being a bit slower with it. So have bumped up PoPs in general this afternoon, with rain being the only hope of some relief from the heat. Highs should end up between 99F and 102F most places. Some isolated showers/storms may hang around into the overnight hours, but whatever is left should weaken tonight. Given high dewpoints and warm airmass, its unlikely that lows fall much lower than the mid 70s tonight, with some (especially in urban areas) potentially remaining near 80F overnight. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Key Message(s): - Heat Indices as high as 110 degrees Saturday. A Heat Advisory may be needed. - Scattered to numerous showers and thunderstorms this weekend. - Isolated Flash Flooding threat over the weekend. Main upper trough axis will continue across the middle of the country through the weekend, with some upper ridging still being indicated across the forecast area. At the surface, a decaying surface front will move into the cwa, which will at least enhance lift somewhat. Add in high pwat values above the 2 inch mark, and some instability by the afternoon each day, and we should see scattered to possibly numerous showers and thunderstorms developing bot Saturday and Sunday. High pwat readings and potentially slower moving storms could lead to some heavier rainfall at times. Another day of higher heat indices are expected to be high over the weekend. Afternoon highs in the middle 90s,and a good amount of moisture, will lead to heat index readings above 105 to 110 for a period Saturday. Can not rule out another Heat Advisory through the afternoon, but will wait until the current Advisory expires this evening before possibly pulling the trigger on that. There is still some uncertainty as to exact heat index values, mainly due to when convection starts and how much cloud cover gets created by that. Earlier convection and clouds would keep slightly cooler readings, while later convection and more sunshine will more than likely cause readings to rise to advisory criteria. Sunday will be slightly cooler with more clouds, and this will keep heat index readings between 95 to 105 degrees. && .LONG TERM /MONDAY THROUGH FRIDAY/... Key Message(s): - After Monday, heat indices climb back over 100 degrees. - Daily diurnal convection expected. We get back into a slightly more typical Summertime pattern through the week. Pwat values remaining relatively high, at or above 2 inches, with continued upper ridge just off the east of the region across the western Atlantic. The main upper trough axis continues to be west of the area, with stronger dynamics deflecting further off to the north through the period. With plenty of moisture, and afternoon highs forecast in the low to mid 90s each day, much of the guidance shows high likelihood for diurnal showers and thunderstorms. With the high pwat values, any slow moving storms could produce periods of heavy rainfall. In addition, can not rule out an isolated severe thunderstorm threat. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... VFR conditions expected through the TAF period. Cumulus has developed in earnest this afternoon as the surface has heated up quickly. Some of this has yielded towering CU and even some showers near CAE/CUB. This will likely remain isolated enough to not include at either site. Better chances for showers/storms will arrive at AGS/DNL this afternoon, with VCSH looking reasonable for a couple of hours there. Vis restrictions are probable if a shower/storm passes directly over a site given how much moisture is in the atmosphere; otherwise, restrictions are not expected at all through the period. Strong low-level jet should prevent stratus or fog tonight. Winds are generally expected to be out of the south or southwest between 5 and 10 knots. Showers/thunderstorms are expected at all TAF sites tomorrow but should be after 18z. EXTENDED AVIATION OUTLOOK...Restrictions possible in diurnally driven convection each day. The greatest convective coverage expected Sat/Sun afternoon. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory until 8 PM EDT this evening for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Heat Advisory until 8 PM EDT this evening for GAZ040-063>065- 077. && $$