An air carrier Captain reported encountering weather enroute that led to a diversion.

Narrative

Enroute to MLI; Dispatch called us on Commercial Radio about 150nm from MLI to update us on the severe squall line that was approaching MLI (our destination). Dispatch added a second alternate of Cedar Rapids that was not on our original release. Our first alternate was Appleton. About 80nm from MLI we could see on the wx radar that the wx at MLI was too severe to approach or land at MLI. A line of magenta and red cells with hooks and shadows stretched from Burlington to MLI and then hooked to the right over to ORD. Current wx at MLI was below landing mins. 100' and 1 mile. The only approach available was 13/8 and 500' LOC approach 6500' runway. There was severe wx approaching MLI. Analyzing the radar and working with ATC we realized that the only way to get to our alternate was to go through severe wx or back track many miles to circumnavigate the wx. We chose instead to turn around and land at ZZZ1 which was only 60 miles away and had good wx. We could not raise Dispatch to let them know of our diversion. The wx was closing in fast. 20 minutes after landing severe wx hit the airport. We kept the passengers on board due to heavy rain; lightning; and winds. After the wx passed we got redispatched to MLI.