Interlaken from Luzern: to stay the night or pass on through?

Do you want big OTT mountains, or a nice lakeside town (slightly less mountainous than Luzern).
If you want the mountains, stay not in Interlaken, but in one of the smaller locations further into the mountains south of Interlaken: Lauterbrunnen, Mürren, Wengen or Grindelwald. For info and hotels: https://jungfrauregion.swiss/en/summer/
Interlaken is best seen as a"gateway" to these locations.

If you want a placid lake town with views, stay in Montreux.

If you want my opinion, this is what Lauterbrunnen looks like (photo): https://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/1_lauterbrunnen_valley_2012b.jpg/1280px-1_lauterbrunnen_valley_2012b.jpg

The idea of a half-day around Interlaken doesn't make much sense to me. I think I'd either go there and sleep there and "make myself available" to any cloud break within 24 hours, or else skip it altogether. But if the predictions hold for both 50% chance of showers during every morning hour and 95% chance of thunderstorms during every afternoon hour on 5/23, then you're not going to see much onboard the Golden Pass line, either. You might consider which museums you have not yet visited in Lucerne or could visit in Bern via faster train. Also see if you can buy an interesting book before leaving Luzern.

You've gotta ask yourself one question: "Do I feel lucky?"

Thanks for the helpful advice Laura and Chris! I’m going to watch the weather today and see what happens. Fingers crossed the thunderstorms move on so I can explore the areas around Interlaken!

Just because there are thunderstorms around - and there are, based on the projections I saw this morning - by no means indicates that there will be storms all day, nor that they will necessarily be where you are.

The Berner Oberland is famous for creating its own weather unlike that just a few miles away.

Often the big storms - if there are any - are in the later afternoon and evening, and the morning in the mountains are often clear in the morning and clouds boil up around lunchtime. They often blow through.

I remember one year having descended to Interlaken for dinner there was an absolutely huge thunderstorm right over me. The light and echoing noise were incredible. I went back up the hill a little later and it hadn't even rained. Sometimes it the opposite. Many years ago before I realized how mistaken I was to stay in Interlaken I was staying at the late lamented Fritz Hutmacher's Hotel Lötschberg when I heard a huge storm all around me. Nothing at Interlaken West but the area between Lauterbrunnen and Interlaken got well hosed down.

Nigel, thank you! Where do you suggest staying if one stays overnight? I’m going to go early and then see how all plays out. Currently booked at aarburg b&b (based on price and Rick’s rec in his book), but would love to know where is truly worth it.