Single word for "to start earlier"

I'm looking for a word that indicates that a time interval (or event) will start earlier than previously expected. It should contrast with "to prolong", because that's also something that can happen to the same interval (and "prolongation" is already used in that context).

Summary:

"last longer"   -> "prolongation"
"start earlier" -> ???

Context:

We are sending severe weather warnings to customers, mostly a few hours in advance. Sometimes it happens that the severe weather lasts longer than expected, we call that a "prolongation" internally. In this case we may send "prolongation warnings".

Similarly, it can happen that the severe weather starts earlier than expected. The duration may or may not be affected by this (the event can be longer than we anticipated, have the same duration and just start earlier, or it may even be shorter). I've started calling this an "earlification", which transports the meaning, but is a little lacking in elegance.

Just to clarify, these words are used in internal, informal documentation and source code. They are not used in communication with customers.

Solution 1:

For severe weather starting earlier: hastening.

to cause (something) to happen more quickly - MW

Solution 2:

When something occurs earlier than expected, it is premature.

Solution 3:

Consider, early/earliness Oxford French-English Dictionary

early: occurring, developing, or appearing before the expected or usual time

earliness: quality of coming early or earlier in time Wordnet by Farlex

The earliness of the storm caught cars without snow tires or chains

Solution 4:

You may consider prematurely

: happening too soon or earlier than usual : happening, arriving, existing, or performed before the proper, usual, or intended time; especially

From Merriam-Webster

I also like the word over-early because it is fun to say, but I don't think people use it much outside of prose