Down and Dirty:
Set your Recurring check-in frequency to 60 minutes.
Use a jamfHelper script to send the notice, ongoing, on the recurring check-in.
Were you looking to use something built in to the Casper Suite for this, like the policy user interaction settings? I ask because, while certainly possible to use this to send up Notification Center messages, they aren't going to stay on screen for too long. I think NC messages stay up for around 4 or so seconds before they disappear.
There's also jamfHelper in a script, which would let you send up a hud style window for example and use some kind of time out function to have it auto dismiss.
Outside of this, you could look at a tool like Yo, which let's you send up a more persistent Notification Center message that the user would have to dismiss. Not sure if that's what you're really looking for though.
There are some other 3rd party tools which can help as well.
@mm2270 Yes thinking Casper built in, like the interaction settings. Definite down side is the shortness at which the notification presents itself to the user. But considering the lateness that I am beginning to work on this and that we only need it for a day or two, I'm not sure figuring out something 3rd party is something I can dive into.
Sounds like a jamfHelper script might be the way to go, thanks @dpertschi and @mm2270 I'll look into that a little further.
Its not immediately apparent, but its possible to send up a jamfHelper message with no buttons, so it appears as a panel that can't be dismissed right away by the user. An example:
#!/bin/sh
/Library/Application Support/JAMF/bin/jamfHelper.app/Contents/MacOS/jamfHelper -windowType hud -description "Hello" -lockHUD -timeout 5
This sends up:

which dismisses automatically after 5 seconds. Just change the integer value from 5 to however long you need it. I would also consider using the positioning controls in jamfHelper to put it in a corner so its not obstructing the user's documents too much.
@mm2270 beat me to it...
How about something with jamfHelper?
https://jamfnation.jamfsoftware.com/article.html?id=107
/Library/Application Support/JAMF/bin/jamfHelper.app/Contents/MacOS/jamfHelper -windowType utility -title "Important Remider" -icon path /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/AlertCautionIcon.icns -button1 "OK" -description "Mission critical service upgrades are happening tomorrow" -alignDescription center -lockHUD
@mm2270 Been a while since I opened this thread but revisited today and used the "jamfHelper message with no buttons". Very cool, worked perfectly. Thanks very much.