Here is an example where ProbSevere increased from 20% to 97% within 18 minutes (2218 to 2240 UTC) (click image to animate):

A three-body scatter signature (TBSS) developed at the end of this time frame, indicating the presence of hail aloft.

By 2248 UTC, MRMS indicated 65.5 dBZ at -20C:

This is another example where the rapidly increasing ProbSevere indicated an intensifying storm. A severe thunderstorm warning was issued for the storm.

Polarimetric Researcher