Persistence Forecast
Saturday, August 8, 2026 · 6:21 AM
Lyrics
EIGHTH OF AUGUST! EAST OF I-65! ONE POINT EIGHT INCHES PWAT! AIR IS LEAD! NO STEERING FLOW! NO COLD FRONT! NO SURFACE FORCING! SOUTH OF I-40 BURNS! STATIONARY DOWNPOURS! PULSE CONVECTION! OUTFLOW COLLISION! HEAT INDEX ONE HUNDRED FIVE! LOCALIZED FLASH FLOODING! TRAPPED IN ZONAL FLOW! TRAPPED IN ZONAL FLOW! NO RELIEF! PERSISTENCE FORECAST! BORDERLINE ADVISORY! THE BOUNDARY STALLS! AIRMASS SOGGY! NO FRONT IN SIGHT! NO FRONT IN SIGHT! SINK!
The forecast discussion
KEY MESSAGES
Updated at 621 AM CDT Sat Aug 8 2026
- Scattered afternoon/early evening showers and storms each day.
Low coverage west of I-65 with medium coverage east of I-65.
- No severe weather is expected, but any storm has the potential to produce gusty winds around 40 mph and heavy downpours causing localized flash flooding.
- Heat index values in the upper 90 to low 100s this weekend, approaching 105 each day next week.
SHORT TERM
(Tonight through Sunday Night) Issued at 1026 PM CDT Fri Aug 7 2026
Things have finally simmered down after another afternoon of active convection.
Expect a very similar situation to unfold this weekend with afternoon storms producing outflow boundaries that trigger new storms through sunset.
Over the weekend, the highest PoPs (60-80%) are concentrated south of I-40 and east of I-65, but almost all of Middle TN has at least 30% PoPs each day.
This is all due to a high moisture content - PWATs in the upper quartile near 1.8 inches - and a lack of forcing at the surface or steering flow in the upper levels.
This leaves storms with very slow motions, creating heavy stationary downpours leading to isolated instances of flash flooding.
LONG TERM
(Monday through next Saturday) Issued at 1026 PM CDT Fri Aug 7 2026
Not much is different in the long term forecast.
Forecast surface analyses don't have anything on the horizon that could be qualified as a bonafide cold front in Middle TN until well beyond the forecast period.
PoPs are in the 40-50% range pretty much every day with hot and humid afternoons.
Moving into next week, the airmass becomes a little more soggy and thus increases heat indices back into the triple digits through at least Thursday.
It looks pretty borderline with Heat Advisory criteria right now, so this will be something to monitor on a day-to-day basis next week for heat headlines.
The upper level flow looks pretty much zonal each day, leading to a persistence forecast of afternoon showers and thunderstorms with hot and humid conditions through next week.