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Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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611 FXUS62 KCAE 161759 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 159 PM EDT Tue Jul 16 2024 .SYNOPSIS... Shower and thunderstorm chances increase during the mid-week period as a trough sets up over the eastern US and a cold front approaches from the northwest. This boundary is expected to stall over the Southeastern US during the late week period keeping elevated rain chances in the forecast. A gradual decrease in daytime temperatures can be expected through Friday. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Hot and humid conditions once again with heat indices of 105+, resulting in a Heat Advisory for the eastern central and eastern Midlands. - Isolated to scattered thunderstorms possible once again this afternoon and evening, with some strong winds possible. Upper level trough over the upper Midwest this afternoon which is expected to amplify a bit by this evening. A southern stream low was located over TX with trough extending to the northeast to TN. Short wave noted over north AL with convection developing ahead of it in northwest GA. Upper ridging continues over SC/east GA with axis over the Piedmont. At the surface, the Piedmont trough remains in place with weak surface convergence noted into the Midlands at 16z. Precipitable water remains high near 2 inches with lower values to the west. The air mass is moderately to strongly unstable at the moment mainly due to strong diabatic heating and resulting steep low to mid level lapse rates around 8.5C/km. With some mixing some drier low- level air this afternoon, expect surface CAPE around 2500-3000 J/kg. The overall forcing today looks a little weaker than yesterday with short waves mainly to the northwest of the area. Convection may be focused near weak surface convergence near the Piedmont trough/west Midlands/CSRA and sea breeze in the east. Also, outflow boundaries from yesterday. The 12z HRRR shows limited convective coverage, while the overall HREF suggests scattered. NBM suggests scattered, so continued low chance pops for the entire area this afternoon into the early evening then diminishing. Temperatures running a little cooler than yesterday at this time but expect highs in the mid to upper 90s. With the high humidity, heat advisory for the east Midlands appears on track. Muggy again tonight with lows in the mid to upper 70s. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... Key Message(s): - Scattered to numerous showers and thunderstorms expected during the afternoon and evening which may produce locally heavy rainfall - A few thunderstorms may be strong with gusty winds as the primary hazard - Continued hot and humid but with lower Heat Index values Upper trough will continue to dig into the eastern half of the CONUS in response to a building ridge out west. Meanwhile, PWATs will remain between 1.75 and 2.25 inches as moisture continues to move into the region around the Bermuda High. The continued lack of steering flow combined with the high moisture could result in areas of localized heavy rainfall and potential hydrological issues due to slow moving and/or training thunderstorms. The Day 2 CSU MLP highlights a large area of higher wind probabilities that stretches from the Pee Dee through Massachusetts. Given adequate instability and inverted-V soundings, would not be surprised if we see a few stronger thunderstorms which could produce locally gusty winds and perhaps hail as well, similar to what we saw yesterday. Another hot and humid day is expected with forecast peak heat index values just below criteria. Will need to monitor for the possibility of one more day of heat products but the likelihood appears lower at this time. Having said that, time outdoors should be limited during peak heating regardless of whether a Heat Advisory is issued. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Key Message(s): - A stalled frontal bounday will keep shower and thunderstorm chances in the forecast through the period - Near to below normal daytime temperatures expected starting on Friday A cold front approaches the region on Thursday, stalling across the Southeastern US. The front, combined with passing short waves, are expected to promote the development of scattered to numerous showers and thunderstorms each day through the extended with widespread rain most likely Thursday and Friday. The potential for locally heavy rainfall and possible flash flooding in addition to a few stronger thunderstorms producing localized wind gusts will continue through the long term. Due to the expected increase in cloud cover and higher rain chances, temperatures are expected to be lower on Thursday with near to below normal values likely for the remainder of the period. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR conditions generally expected through the TAF period. Weak surface trough over the area may provide some convergence. Air mass is moderately to strongly unstable. Scattered cumulus will develop through the afternoon. Forcing for convection limited to low level convergence. Expect scattered thunderstorms this afternoon but confidence too low to include in terminals at this time. Any convection should diminish after 00z. So scattered cumulus with some higher mid level clouds by evening. Winds southwest 10 knots with a few higher gusts this afternoon. Models show a low-level jet tonight around 20 knots so south- southwest winds may stay up overnight but less than 10 knots. EXTENDED AVIATION OUTLOOK...Typical summertime afternoon showers and thunderstorms may cause periodic restrictions each day with abundant moisture causing possible, brief early morning restrictions around sunrise. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory until 7 PM EDT this evening for SCZ016-022- 027>029-031-037-038-041-115-116-135>137. GA...None. && $$