This can be done, there are limitations but for the most part you can tune and configure this using the following steps to start: https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClGjCAK
Not sure what those look like as I am not experiencing low disk issues atm but if you cannot set up a filter on anything in the logs (like this)
Then maybe you can set up an email alert in your SNMP monitoring solution (if you do not have one then you can get a free version of PRTG, or use LibreNMS which is free and supports PAN devices very well)
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