Post-Tropical Cyclone Helene Discussion Number  18
NWS National Hurricane Center Miami FL       AL092024
400 PM CDT Fri Sep 27 2024

Helene has been producing catastrophic flooding over portions of
the southeast U.S. and southern Appalachians, and the associated
heavy rains are shifting westward into the Ohio and Tennessee
Valleys.  Satellite images and surface observations indicate that
Helene has completed extratropical transition, and the initial
intensity is set at 30 kt.

The cyclone is moving to the north-northwest at 15 kt.  A slowdown 
is expected tonight, and the cyclone is forecast to stall over the 
Tennessee Valley this weekend, likely resulting in continued and 
prolonged rainfall.

This is the last tropical cyclone discussion issued by the
National Hurricane Center on Helene.  Future information on
this system can be found in discussions issued by the Weather
Prediction Center beginning at 1000 PM CDT, under AWIPS header
TCDAT4, WMO header WTNT44 KWNH, and on the web at
www.hurricanes.gov.

Rainfall forecasts for the United States can always be found at
https://www.wpc.ncep.noaa.gov/qpf/qpf2.shtml
and outlooks of flash flood risks can be found at
https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php
.

KEY MESSAGES:

1. Historic, catastrophic and life-threatening flash and urban 
flooding, including numerous major landslides, will continue across 
portions of the southern Appalachians through this evening, followed
by gradual improvement tonight and into Saturday.  Widespread 
serious river flooding is ongoing, some of which will be major to 
record breaking.

2. There is a possibility of long-duration power outages in
portions of the southeast U.S.  If you use a generator, be sure it
is placed outside at least 20 feet away from doors, windows, and
garages to avoid deadly carbon monoxide poisoning.

3. Use caution after the system passes as deadly hazards remain
including downed power lines and flooded areas.


FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 37.5N  85.5W   30 KT  35 MPH...POST-TROPICAL
12H  28/0600Z 37.9N  87.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
24H  28/1800Z 37.7N  87.2W   20 KT  25 MPH...POST-TROP/EXTRATROP
36H  29/0600Z 37.5N  87.3W   20 KT  25 MPH...POST-TROP/EXTRATROP
48H  29/1800Z 37.3N  87.0W   20 KT  25 MPH...POST-TROP/EXTRATROP
60H  30/0600Z...DISSIPATED

$$
Forecaster Cangialosi