Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 222256 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 656 PM EDT Sat Jul 22 2017 .SYNOPSIS... Upper ridging will remain over the forecast area today then weaken Sunday into early next week. Along with the troughing moisture will increase across the area with slowly increasing chances of thunderstorms through Wednesday. It will remain hot this weekend with heat index values peaking between 105 and 115 degrees. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Subtropical ridging will continue to extend into the region through tonight. Lee side troughing will remain over the Upstate. Isolated convection developed early this evening in the CSRA...otherwise lack of trigger and high LFC/weak cap limiting development. Main threat appears to be locally heavy rain with precipitable water near 1.7 inches in moderately unstable air mass. Any convection should diminish rapidly after sunset. Overnight low temperatures in the middle 70s. Fog is not expected due to a well mixed boundary layer.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Synoptic situation will continue changing Sunday and Monday as the upper level trough digs into the eastern US and the upper level ridge retreats to the south. Southwest winds on Sunday will push Gulf moisture northward with PWAT values exceeding 2 inches from the late morning hours through Monday night. Instability will again be moderate to strong Sunday...however minimal divergence aloft will work to suppress convection. As such expect a slight increase in pops due to the combination of moisture and instability on Sunday and with slightly better flow aloft Monday another slight increase in pops. With the freezing level above 15 kft expect the main threat from thunderstorms to remain damaging wind gusts...however with slow storm movement expected will also need to monitor for locally heavy rainfall. With the upper level trough over the eastern US and increased cloud cover temperatures will moderate slightly with afternoon highs in the mid 90s Sunday and low 90s Monday. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Models remain in good agreement through the long term with the upper level trough exiting the region Tuesday then returning Thursday through Saturday as the next system drops from Canada into the Great Lakes region. This will keep the forecast area stuck between the upper level ridge to the south and the trough to the north and under an influx of Gulf moisture. As such have remained with chance pops through the long term with temperatures near normal with highs in the low 90s and lows in the low to mid 70s. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... VFR conditions expected for a majority of the TAF period. Isolated showers and thunderstorms are expected to develop later this afternoon with coverage diminishing this evening. So far this afternoon, convection has been confined well west of the terminals, in the Upstate of South Carolina and northeastern Georgia. With low coverage of storms and low confidence in exact timing, have decided not to include any mention in the TAFs at this time. Will continue to monitor radar trends and make updates as necessary. Models are indicating a 25 knot low level jet developing overnight, so believe this will preclude fog development in most locations. The HRRR is not showing any early morning fog even at fog prone AGS and OGB, which increases confidence in low fog potential. There will be a chance for shower and thunderstorm development again on Sunday, but the most likely timing will be after 18Z, so have not included mention in current TAF issuance. EXTENDED AVIATION OUTLOOK...Increasing chances of afternoon/evening thunderstorms, and late night/early morning fog/stratus, Monday through Wednesday. && .CAE WATCHES/WARNINGS/ADVISORIES...
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GA...None. SC...None.
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