Shortcode with variables for location values not working

I am using WP Wunderground, WP Geolocation JS and PHP Shortcode.

I am attaching the city and state of the visitor to variables like so:

$weathercity = do_shortcode('[mmjs-city]');
$weatherstate = do_shortcode('[mmjs-regionname]');

I can echo those locations within a page or post using the PHP Shortcode plugin like so:

[php]
$weathercity = do_shortcode('[mmjs-city]');
$weatherstate = do_shortcode('[mmjs-regionname]');
echo $weathercity .', '.$weatherstate;
[/php]

Which essentially renders something like Chicago, Illinois.

I can echo a shortcode using the PHP Shortcode plugin like so:

[php]
$weathercity = do_shortcode('[mmjs-city]');
$weatherstate = do_shortcode('[mmjs-regionname]');
echo $weathercity .', '.$weatherstate;
echo '[forecast location='.$weathercity.', '.$weatherstate.']';
[/php]

It will actually spit out the shortcode as :

[forecast location="Chicago, Illinois"]

However, if I try to run do_shortcode on the last line like so:

[php]
$weathercity = do_shortcode('[mmjs-city]');
$weatherstate = do_shortcode('[mmjs-regionname]');
echo $weathercity .', '.$weatherstate;
echo do_shortcode('[forecast location='.$weathercity.', '.$weatherstate.']');
[/php]

The weather does not show up at all. Any ideas on how I can handle this? I really just want to be able to sniff the location of the user and display weather for that location.

http://wordpress.org/extend/plugins/wunderground/