Update-feeds issue

[PL2588]

I am working on creating a weather server using FoF that constantly
gets storm information via an rss feed from noaa.gov. For instance
this in a link to one of my rss feeds http://www.weather.gov/alerts/wwarssget.php?zone=OHZ009
Everything has worked great so far except that it only updates when
there actually are storms but never updates again once the rss feed
has changed back to its normal state meaning that the warnings and
watches are over. is there anyway to get it to capture the rss feed
that says

There are no active watches, warnings or advisories in Ohio (Erie/
OHZ009)

when it updates.