Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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286 FXUS62 KCAE 050005 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 805 PM EDT Thu Jul 4 2024 .SYNOPSIS... Atmospheric 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 /UNTIL 6 AM FRIDAY MORNING/... Key Message(s): - Muggy conditions overnight with lows well above average. Cumulus clouds dissipating as the sun sets this evening. Some high cirrus clouds across the north coming over the top of the upper level ridge centered southwest of the area. As the surface ridge has moved offshore and a cold front approaches the forecast area, a strengthening southwesterly low level jet develops overnight which will increase low level moisture as well as keep low temperatures warm overnight. Expect muggy conditions overnight as a result with low temperatures near the daily record max in the mid to upper 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Key Message(s): - A Heat Advisory is in effect from 11am to 8pm Friday - Low threat of severe thunderstorms and flash flooding Saturday Heat: Moisture increases on Friday pushing Heat Index values up to 110. MOS dewpoints in the afternoon are in the low to mid 70s which are several degrees higher than the previous day. With warming 850mb temps and only widely scattered convection expected, we will likely see highs in the upper 90s to around 100 degrees. Despite PWAT values around 1.7 to 1.9 inches, upper ridging over the FA should be sufficient to suppress widespread convection. Dewpoints continue to increase on Saturday with PWAT values over 2 inches. However increased convergence ahead of a front and some shortwave energy moving into the region will promote higher convective coverage than Friday. So confidence in a Heat Advisory for Saturday is limited. Convection and cloud cover should keep us cooler than Friday. Thunderstorms: An upper level trough will move into the Great Lakes region then into New England this weekend. The associated front will remain west of the area however increased convergence ahead of the front and rising atmospheric moisture will lead to scattered or numerous showers and thunderstorms for Saturday afternoon. Shortwave energy rounding the base of the trough may also support convection in the afternoon and evening. PWAT values as high as 2.5 inches indicates potential for flash flooding however the threat will be hampered by 10 to 20 kt cloud layer winds. The flash flooding potential may be limited to training storms or urban areas. A tall, skinny CAPE profile suggests limited updraft strength but precip loading may promote isolated downbursts in some of the deeper storms. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Key Message(s): - Daily afternoon thunderstorms expected for much of the period A fairly persistent synoptic pattern dominates the long term period. Global ensembles favor positive 500mb height anomalies over the Southeast with mean PWAT values very steady around 2 inches through the end of the long term. With near or above normal atmospheric moisture and weak ridging in place, we would expect a common summertime pattern of diurnal showers and thunderstorms with temperatures near or a little above normal. As is typical for the season, there could be an isolated severe threat each day. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... VFR conditions expected through the TAF period. Cumulus have generally dissipated as heating quickly wanes. with scattered cirrus expected to cross the region overnight. Concern for the period remain potential for early morning fog and stratus. This is complicated by particulates from area fireworks displays. Although moisture has been gradually increasing there will be a 20 knot LLJ over the area so the potential is lowered and have remained without mention of early morning and sunrise restrictions. Will continue to monitor and for impacts of fireworks displays. With sunrise and onset of mixing cumulus will once again begin developing with winds turning more southerly through the day with speeds remaining 10 knots or less. Convection will be possible near the end of the TAF period however confidence in timing and coverage remain too low to include. 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 minimize 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 to 8 PM EDT Friday for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Heat Advisory from 11 AM to 8 PM EDT Friday for GAZ040-063>065- 077. && $$