The real time weather feature on FlightGear is broken due to noaa.gov website moving http to enforce https traffic instead.

Based on this post https://forum.flightgear.org/viewtopic.php?f=17&t=35343#p343940 it is a known bug and seems to have been fixed in the git repo.

For those who don't want to git clone and build from source there is an simple alternative: Setup an HTTP Proxy 

The following steps were executed in Linux, it shold be simple to implement on Windows or Mac:

1. Edit /etc/hosts and added the following entry:

$ sudo echo 127.0.0.1 tgftp.nws.noaa.gov. >>/etc/hosts

2. Install Apache web server:

$ sudo apt install apache2

3. Update default server virtualhost  in /etc/apache2/sites-available/000-default.conf configuration to:

<VirtualHost *:80>
#ServerName www.example.com
ServerAdmin webmaster@localhost
DocumentRoot /var/www/html
#LogLevel info ssl:warn
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
#Include conf-available/serve-cgi-bin.conf
ProxyRequests Off
ProxyPreserveHost On
SSLProxyEngine on
<Proxy *>
Order deny,allow
Allow from all
</Proxy>

ProxyPass "/data/observations/metar/stations/" "https://140.90.101.79/data/observations/metar/stations/"
ProxyPassReverse "/data/observations/metar/stations/" "https://140.90.101.79/data/observations/metar/stations/"

</VirtualHost>

4. Enable proxy and ssl modules:

$ cd /etc/apache2/mods-enabled
$ sudo ln -s ../mods-available/proxy.load
$ sudo ln -s ../mods-available/proxy.conf
$ sudo ln -s ../mods-available/ssl.load
$ sudo ln -s ../mods-available/ssl.conf
$ sudo ln -s ../mods-available/proxy_http.load
$ sudo ln -s ../mods-available/proxy_http2.load

5. Restart Apache:

$ sudo apachectl stop; sudo apachectl start

Have fun!