000 FXUS64 KOHX 211134 AFDOHX Area Forecast Discussion National Weather Service Nashville TN 634 AM CDT Sat Aug 21 2021 .UPDATE... FOR 12Z AVIATION DISCUSSION. .DISCUSSION... Potential flooding/flash flooding scenario setting up through late today, especially around and on the west side of I24. Healthier moisture source currently below H70 but strong moisture advection will kick in shortly, and by late morning, moisture will have become very deep. Several models showing PWATs 2.2-2.5 range by midday over much of the area. Instability will not become excessively high and shear will stay low end, but a SFC/LL boundary cutting across our west and an incoming upper wave will help plenty in developing numerous showers and storms, with storms possibly producing heavy rainfall/localized flooding. Many showers/storms expected to pop up early this morning, with the main flood threat toward sunrise and into the afternoon. This SFC/LL boundary does look to wash out in the afternoon, and with the upper wave largely east of us, we should see some decrease in coverage overall later today. However, instability remains pretty good and moisture abundant into early tonight, and redevelopment over the watch area very possible mid/late afternoon. Thus have updated Flood Watch to run through 3 PM. Big decrease in coverage is really more so as we go through the evening. On Sun, and upper ridge finally builds, and holds largely into Tue night. Compared to the recent activity, Sun-Tues will see a dramatic decrease in showers/storms with possibly isolated storms popping up mostly in the afternoon heat. Sun afternoon looking like best chance during this period. Upper ridge does weaken mid-week and on Thu a weak frontal boundary sets up across the southern OH valley. This pattern will bring a good increase of shower/storm activity back to the area for late week, especially if a weak upper low forms over the deep south which a few models suggest. .AVIATION... 12Z TAF DISCUSSION. BNA/MQY/CKV/CSV...Messy set of TAF`s this morning. A surface boundary has set up just west of Nashville and has provided the focus for a band of excessive rainfall and is moving slowly eastward. We`ll start the TAF`s with generally low ceilings and visibilities owing to widespread showers, with TEMPO TSRA/CB`s for the embedded convective cells. Rain should gradually lessen in intensity and coverage during the next several hours while ceilings improve, but the HRRR brings in another round of storms later this afternoon. .OHX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 3 PM CDT this afternoon for Bedford- Cheatham-Dickson-Giles-Hickman-Houston-Humphreys-Lawrence-Lewis- Marshall-Maury-Montgomery-Perry-Stewart-Wayne-Williamson. $$ DISCUSSION......07 AVIATION........08