Current Radar
Attention Turns To Heavier Rain Wed. PM – Thurs. PM
A surface low is expected to track from the Gulf Coast northward along the Mississippi River, increasing shower/thunderstorm activity across much of the mid-south. Rainfall here in Nashville could accumulate to 1″+ in some spots, considering the strength of this system. No severe weather is expected at this time.
GFS Forecast, Wed. 6PM – Fri. 12PM

Let’s compare rainfall totals…the GFS model (only computer guidance) versus the Weather Prediction Center’s human-refined forecast:
GFS Forecasted Rainfall through Friday 12PM…

…versus WPC Rainfall Forecast through 6AM Friday

Bottom line: it appears that 1″ of rain by Friday at noon is likely. Whether some spots receive 1.50″ or greater seems to be based on rainfall rates, which could be fairly steady on Thursday.
Thundery Weekend Weather
NWS Nashville thinks Saturday night through Sunday could be a bit bumpy:
In the ext fcst, An unsettled and mild pattern can be expected
through the period, for the most part. A strong storm system will
bring showers and some tstm activity Sat nt and Sun. An upper level
low will track across the southeastern U.S. by Monday and may bring
some cooler temps and some additional rainfall. read more