Areal Flood Advisory 112, NWS Nashville, TN

Area Forecast Discussion
National Weather Service Nashville TN
202 PM CDT Sat Aug 28 2021

.DISCUSSION...

High pressure continues to dominate the weather across Middle
Tennessee both at the surface and aloft. Scattered cells have been
developing in this warm, humid air mass, most notably along the
Cumberland Plateau. In fact, the special 18Z sounding from OHX
shows a SBCAPE of 3,133 J/kg, a Lifted Index of -7, and a PWAT of
1.84". So the instability is definitely present. Tomorrow will be
similar to today, with isolated/scattered convection mainly in the
afternoon and typical temperatures for late August. High pressure
will start to break down Sunday night and Monday as Ida comes
onshore the Louisiana coast and begins its trek toward Middle
Tennessee. So look for POP's to begin increasing on Monday and
Monday night, with the heaviest rainfall expected on Tuesday and
Tuesday night. The latest GFS places the center of the low just
west of Nashville at 18Z Tuesday, while the Euro at the same time
places the low center near Corinth, MS. While there are
differences in timing, both models bring the extratropical low
center directly across Middle Tennessee. Fortunately, drying
behind the low should be quick as this system makes a quick exit
to the northeast. The most recent WPC QPF from 00Z Tuesday until
12Z Thursday gives us widespread 4" to 5" across all but the
Cumberland Plateau, which is not something we wish to happen given
the catastrophic flooding that occurred here exactly one week
ago. Needless to say, rainfall amounts of this magnitude will
greatly increase the risk of more flash flooding and also river
flooding, and these are the threats we're most focused on at this
time.

&&

.AVIATION...
18Z TAF DISCUSSION.

Generally VFR are expected through the TAF. Rain and some thunder
is occurring closest to CSV but may move in the direction of
MQY/BNA in the next few hours. VCTS/VCSH was used to handle this
afternoon's convection with low confidence in specific terminal
impacts. Rain will dissipate after 00z-01z.

Southerly winds remain at or below 10 kts, becoming nearly calm
overnight.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      73  91  73  88  71 /  10  40  10  50  60
Clarksville    72  90  72  86  70 /  10  40  10  60  60
Crossville     69  86  68  84  67 /  10  30  10  40  40
Columbia       71  89  71  87  69 /  10  30  10  50  70
Lawrenceburg   71  89  71  86  69 /  10  30  10  50  60
Waverly        73  90  72  86  70 /  10  40  10  50  70

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DISCUSSION......08
AVIATION........Schaper

Hazardous Weather Outlook
National Weather Service Nashville TN
500 AM CDT Sat Aug 28 2021

TNZ005>011-023>034-056>066-075-077>080-093>095-291000-
Stewart-Montgomery-Robertson-Sumner-Macon-Clay-Pickett-Houston-
Humphreys-Dickson-Cheatham-Davidson-Wilson-Trousdale-Smith-Jackson-
Putnam-Overton-Fentress-Perry-Hickman-Lewis-Williamson-Maury-
Marshall-Rutherford-Cannon-De Kalb-White-Cumberland-Bedford-Coffee-
Warren-Grundy-Van Buren-Wayne-Lawrence-Giles-
500 AM CDT Sat Aug 28 2021

This Hazardous Weather Outlook is for Middle Tennessee.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Hurricane Ida is forecast to make landfall in Louisiana on Sunday
night, then turn northeast and weaken to a Tropical Depression as it
moves near or across Middle Tennessee from Tuesday into Wednesday.
Although the amount of rainfall we receive will be highly dependent
on the track of Ida, current indications are that 2 to 4 inches of
rain, with some locally higher amounts, is possible during this
timeframe. This may lead to localized flooding issues. In addition,
damaging wind gusts and an isolated tornadoes cannot be ruled out as
the remnant low crosses our area.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed next Tuesday & Wednesday depending
on the future track of Hurricane Ida.

Adcock