Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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733 FXUS62 KCAE 061112 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 712 AM EDT Sat Jul 6 2024 .SYNOPSIS... Moisture increases today with scatter to numerous showers and thunderstorms expected this weekend. 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 from 11am to 8pm for heat index values up to 110 degrees. - Scattered to numerous showers and thunderstorms. - Isolated Flash Flooding possible Temperatures this morning remain quite warm in the upper 70s and lower 80s with some convective debris clouds over the western Midlands. This may set the stage for another hot day with high heat index values. Water vapor imagery shows an upper trough moving through the Great Lakes region with the upper ridge holding strong across Florida and south Georgia. At the surface, an weakening frontal boundary is expected to push into the forecast area this afternoon, which may aid in providing a focus for convective initiation. Instability is forecast to be moderate with MLCAPE values 500-1000 J/kg, though wind shear remain generally weak. The axis of deeper moisture with PWATs around 2.3-2.5 inches will combine with instability and low level moisture convergence to promote scattered to numerous thunderstorms initiating after 16z-17z with better coverage across the forecast area compared to yesterday, with some sea breeze interaction as well over the eastern Midlands. Overall severe threat appears low but cannot rule out an isolated severe thunderstorm threat, but think there is an isolated flash flood threat as well with any training storms due to the excessively high atmospheric moisture and WPC has the area outlooked in a slight risk for excessive rainfall. Storms are likely to linger into the overnight hours due to interacting outflow boundaries until the instability wanes after midnight. The combination of high temperatures and elevated dewpoints and humidity should result in heat advisory criteria being met across the forecast area. Confidence is a bit lower today given the expectation of more widespread convection, depending on when it develops. Heat indices could reach as high as 110 degrees before storms develop. Overnight lows expected to be very warm again in the mid to upper 70s. && .SHORT TERM /SUNDAY THROUGH MONDAY/... Key message(s) - Not as hot with an increase in convective activity. A fairly static upper level pattern will be in place across the Eastern U.S. early next week with an level trough over the Upper Great Lakes and Central Mississippi River Valley and a downstream H5 ridge over the Southeast U.S. A diffuse frontal boundary over The Midlands and CSRA will be the focus for an increased probability of showers and thunderstorms on both days. More extensive cloud cover should result in high temperatures closer to normal for early July. In addition, precipitable water values in excess of two inches will increase the risk of locally heavy rainfall near stronger thunderstorms. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Key Message(s) - More typical summertime weather across the region. High pressure aloft should be over the Western Atlantic Ocean next week and the upper level trough over the Great Lakes weakens as the week goes on. Precipitable water levels will remain in excess of two inches. Scattered to numerous afternoon and evening thunderstorms are expected each day with the potential for locally heavy rainfall. Temperatures will be near to slightly above normal for mid July. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... VFR conditions generally expected through the TAF forecast period with afternoon convection expected. A frontal boundary is expected to stall near the area today providing a focus for shower and thunderstorm development this afternoon. Winds expected to be light and variable through sunrise, then pick up from the south around 5 to 7 knots late morning. Abundant moisture with increased instability should result in numerous showers and thunderstorms this afternoon and have included this in the forecast mainly from 20z to 00z. IFR vsby in heavy rain possible along with variable gusty winds. Stratus development is also anticipated late in the TAF period. EXTENDED AVIATION OUTLOOK...Restrictions possible in diurnally driven showers and thunderstorms each day. Sunday is expected to have the highest coverage in the extended period. && .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. && $$