Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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923 FXUS62 KCAE 050837 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 437 AM EDT Fri Jul 5 2024 .SYNOPSIS... Moisture increases into the weekend with isolated to scattered showers and thunderstorms each day beginning Friday. Above normal temperatures are expected Friday and 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. The primary mid-upper level ridge axis continues to pivot east and is starting to show signs of flattening ahead of the approaching trough in the central US. Thanks to the ridge shifting east, southerly low level flow has driven up both surface dew points and PWAT`s, in the low-mid 70`s and nearing 2.0" respectively. The combination of increasing moisture and persistent ridging will allow heat indices to rise above 105 today, likely over 110 in spots; NBM 75th percentile high temp today is 104 at CAE, but increasing moisture and cloud cover should prevent us from quite reaching that. So "only" forecasting a high at CAE of 102 with afternoon dew points in the low 70`s. While moisture and boundary layer heat are increasing, shower- storm activity will remain limited today as the ridge related capping and subsidence aloft is still very evident in all forecast soundings. The best chances (but still only 20-30%) for convection is across the CSRA and western Midlands where mid- level capping is slightly weaker and the overall moisture- instability is slightly more favorable. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Key Message(s): - Heat Indices as high as 110 degrees. A Heat Advisory may be needed. - Scattered to numerous showers and thunderstorms this weekend - Isolated Flash Flooding threat over the weekend An upper trough will move through the Great Lakes region Saturday while a weak frontal boundary pushes into the Carolinas and stalls near or just west of our forecast area. A very moist air mass will be in place with PWATs well over 2 inches and possibly as high as 2.4 inches. Surface high pressure centered over the western Atlantic will continue to feed moisture into the area with southerly low level flow. Forecast instability is forecast to be higher than it has been and the combination of above normal PWATs, very warm temperatures, instability and low level moisture convergence should result in scattered to numerous showers and thunderstorms both Saturday and Sunday. Cannot rule out an isolated pulse severe threat but widespread severe weather is not expected. Extremely high atmospheric moisture and possible training of storms with very high rain rates may support an isolated flash flooding threat and WPC has outlooked the area in a slight risk of excessive rainfall for Saturday. Heat indices are expected to be high over the weekend with values forecast over 100 degrees and heat advisory criteria may be met on Saturday with forecast heat index values 105 to 110 degrees. Confidence is limited though, with the possibility of convection developing early enough to prevent those values from being reached. && .LONG TERM /MONDAY THROUGH THURSDAY/... Key Message(s): - Heat Indices over 100 degrees - Daily diurnal convection expected A persistent and somewhat stagnant pattern is expected in the extended forecast period with global ensembles favoring positive 500mb height anomalies over the forecast area and mean PWAT values near or in excess of 2 inches through the period. Generally expect scattered diurnal convection each day through the forecast period in a typical summer pattern with near to above normal temperatures. Cannot rule out an isolated severe thunderstorm threat. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... VFR conditions expected through the TAF period. Little to no vsby or cig restrictions are expected this morning thanks to a strong low level jet driving some boundary layer mixing all night; some 6k foot stratus is the only feature of note as of 09z. Southerly winds will pickup later this morning, with gusts up to 12-15 knots this afternoon. Typical summer cu also expected throughout the late morning and afternoon. Shower-storm activity is possible across the CSRA and western Midlands later today, potentially impacting AGS and DNL but confidence is too low for any TAF mention at this time. EXTENDED AVIATION OUTLOOK...Restrictions possible in diurnally driven convection each day. The greatest convective coverage expected Sat/Sun afternoon. && .FIRE WEATHER... Key messages(s): -Hot temperatures will continue through the weekend -Rainfall probabilities increasing Friday through early next week Hot temperatures will continue through the weekend with increasing moisture and chances of showers and thunderstorms Friday into early next week. Although there was some rain late in the weekend and into early this week, the hot and dry conditions over the past few days have generally minimized any improvement from the rain. Moisture has begun increasing over the area and scattered afternoon and evening thunderstorms possible Friday mainly along and north of I-20. Increasing coverage of afternoon and evening showers and thunderstorms are expected to spread across the Midlands and CSRA Saturday through much of next week. Temperatures will also be a concern with afternoon highs in the upper 90s to around 100 which will push heat index values to 110 Friday and between 105 and 110 Saturday. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for SCZ016-018-020>022-025>031-035-037-038-041-115-116- 135>137. GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for GAZ040-063>065-077. && $$